Re: reading file byLine
On Saturday, 7 November 2015 at 17:13:33 UTC, Namal wrote: On Saturday, 5 September 2015 at 14:49:13 UTC, deed wrote: On Saturday, 5 September 2015 at 14:44:19 UTC, deed wrote: .map!(s => chomp(s, "\"") .map!(s => chompPrefix(s, "\"") should be .map!(s => chomp(s, "\"")) .map!(s => chompPrefix(s, "\"")) Hello again, Now I have a file that looks like a b c d e f g h I want to get that in an element of strings but without quatation marks auto a = f.byLine() .map!(a => a.split) .array(); f.close(); Sorry for double post, I pressed accidently 'enter'. How can I ad chomp so the quatation marks are removed?
Re: reading file byLine
On Saturday, 5 September 2015 at 14:49:13 UTC, deed wrote: On Saturday, 5 September 2015 at 14:44:19 UTC, deed wrote: .map!(s => chomp(s, "\"") .map!(s => chompPrefix(s, "\"") should be .map!(s => chomp(s, "\"")) .map!(s => chompPrefix(s, "\"")) Hello again, Now I have a file that looks like a b c d e f g h I want to get that in an element of strings but without quatation marks auto a = f.byLine() .map!(a => a.split) .array(); f.close();
Re: reading file byLine
On Friday, 18 September 2015 at 10:48:25 UTC, Namal wrote:
On Friday, 18 September 2015 at 10:34:41 UTC, Edwin van Leeuwen
wrote:
On Friday, 18 September 2015 at 10:26:46 UTC, Namal wrote:
Hello guys, is there a nice functional way to read the file
which is like
1,2,3,4,5,6
2,3,4,5,6,7
8,9,0,9,2,3
line by line, split numbers and remove each ','
convert it to int and save in a matrix int[][] arr?
Not tested, but I think the following should work:
auto matrix = str
.byLine
.map!((l) => l.split(",")// Split each line
.map!(to!int) // Turn into ints
.array)// Return an array
.array // Copy into an array
And how do tell here to read my file?
Replace str with File("myfile"):
auto matrix = File("myfile")
.byLine
.map!((l) => l.split(",")// Split each line
.map!(to!int) // Turn into ints
.array)// Return an array
.array // Copy into an array
Re: reading file byLine
Hello guys, is there a nice functional way to read the file which is like 1,2,3,4,5,6 2,3,4,5,6,7 8,9,0,9,2,3 line by line, split numbers and remove each ',' convert it to int and save in a matrix int[][] arr?
Re: reading file byLine
On Friday, 18 September 2015 at 10:34:41 UTC, Edwin van Leeuwen
wrote:
On Friday, 18 September 2015 at 10:26:46 UTC, Namal wrote:
Hello guys, is there a nice functional way to read the file
which is like
1,2,3,4,5,6
2,3,4,5,6,7
8,9,0,9,2,3
line by line, split numbers and remove each ','
convert it to int and save in a matrix int[][] arr?
Not tested, but I think the following should work:
auto matrix = str
.byLine
.map!((l) => l.split(",")// Split each line
.map!(to!int) // Turn into ints
.array)// Return an array
.array // Copy into an array
And how do tell here to read my file?
Re: reading file byLine
On Friday, 18 September 2015 at 11:37:15 UTC, Edwin van Leeuwen wrote: On Friday, 18 September 2015 at 11:11:51 UTC, Namal wrote: compiles but crashes For me it works fine. You probably have extra spaces or something in your file. It would help if you posted the error message you get when running the program. Oh, yes, sorry, there was a space after the end of one line
Re: reading file byLine
On Friday, 18 September 2015 at 10:26:46 UTC, Namal wrote:
Hello guys, is there a nice functional way to read the file
which is like
1,2,3,4,5,6
2,3,4,5,6,7
8,9,0,9,2,3
line by line, split numbers and remove each ','
convert it to int and save in a matrix int[][] arr?
Not tested, but I think the following should work:
auto matrix = str
.byLine
.map!((l) => l.split(",")// Split each line
.map!(to!int) // Turn into ints
.array)// Return an array
.array // Copy into an array
Re: reading file byLine
On Friday, 18 September 2015 at 11:06:46 UTC, Edwin van Leeuwen
wrote:
On Friday, 18 September 2015 at 10:48:25 UTC, Namal wrote:
On Friday, 18 September 2015 at 10:34:41 UTC, Edwin van
Leeuwen wrote:
On Friday, 18 September 2015 at 10:26:46 UTC, Namal wrote:
Hello guys, is there a nice functional way to read the file
which is like
1,2,3,4,5,6
2,3,4,5,6,7
8,9,0,9,2,3
line by line, split numbers and remove each ','
convert it to int and save in a matrix int[][] arr?
Not tested, but I think the following should work:
auto matrix = str
.byLine
.map!((l) => l.split(",")// Split each line
.map!(to!int) // Turn into ints
.array)// Return an array
.array // Copy into an array
And how do tell here to read my file?
Replace str with File("myfile"):
auto matrix = File("myfile")
.byLine
.map!((l) => l.split(",")// Split each line
.map!(to!int) // Turn into ints
.array)// Return an array
.array // Copy into an array
import std.file, std.stdio, std.string, std.conv, std.algorithm,
std.array;
void main(){
auto matrix = File("test.txt")
.byLine
.map!((l) => l.split(",")// Split each line
.map!(to!int) // Turn into ints
.array)// Return an array
.array();
matrix.writeln;
}
compiles but crashes
Re: reading file byLine
So do I understand it right: does => in map! indicates a lambda function?
Re: reading file byLine
On Friday, 18 September 2015 at 12:28:29 UTC, Namal wrote:
So do I understand it right: does => in map! indicates a
lambda function?
Yes exactly. There are a number of ways you can define a lambda
function in D. For example if the function is multiline I often
use:
(l) {
...; // do something
return result;
}
More details here http://ddili.org/ders/d.en/lambda.html (half
way down the page)
Re: reading file byLine
On 09/18/2015 05:58 AM, Edwin van Leeuwen wrote:
On Friday, 18 September 2015 at 12:28:29 UTC, Namal wrote:
So do I understand it right: does => in map! indicates a lambda
function?
Yes exactly. There are a number of ways you can define a lambda function
in D. For example if the function is multiline I often use:
(l) {
...; // do something
return result;
}
More details here http://ddili.org/ders/d.en/lambda.html (half way down
the page)
As of a few hours ago, you can go to the book index and search for =>,
or lambda, or anything else. :)
http://ddili.org/ders/d.en/ix.html
(Excuse the page format for now.)
Ali
Re: reading file byLine
On Monday, 14 September 2015 at 18:36:54 UTC, Meta wrote: As an aside, you should use `sort()` instead of the parentheses-less `sort`. The reason for this is that doing `arr.sort` invokes the old builtin array sorting which is terribly slow, whereas `import std.algorithm; arr.sort()` uses the much better sorting algorithm defined in Phobos. Thanks for pointing out.
Re: reading file byLine
On Monday, 7 September 2015 at 10:25:09 UTC, deed wrote: Right, it's like int x = 3; // x + 5; // Just an expression evaluated to 8, // but what do you want to do with it? // It won't affect your program and the // compiler will give you an error. int y = x + 5; // But you can assign the expression to // a new variable x = x + 5; // or you can assign it back writeln(x);// or you can pass it to a function. // For your case: int[] arr = [1, 2, 3, 2, 1, 4]; arr.sort; // Operating on arr in place -> arr itself is mutated arr.writeln; // [1, 1, 2, 2, 3, 4] arr.uniq; // Not operating on arr, it's like the expression // x + 5 (but no compiler error is given). arr.uniq.writeln; // [1, 2, 3, 4] (Expression passed to writeln) arr.writeln; // [1, 1, 2, 2, 3, 4] (Not affected) int[] newArr = arr.uniq.array; // Expression put into a new array assigned to newArr newArr.writeln;// [1, 2, 3, 4] arr.writeln; // Still the sorted array. [1, 1, 2, 2, 3, 4] arr = arr.uniq.array; // Now arr is assigned the uniq array arr.writeln; // [1, 2, 3, 4] You need to know whether the function will mutate your array; sort does, while uniq doesn't. If you want to do things requiring mutation, but still want your original data unchanged, you can duplicate the data with .dup before the mutating operations, like this: int[] data = [1, 2, 2, 1]; int[] uniqData = data.dup.sort.uniq.array; data.writeln; // [1, 2, 2, 1] Unchanged, a duplicate was sorted. uniqData.writeln; // [1, 2] As an aside, you should use `sort()` instead of the parentheses-less `sort`. The reason for this is that doing `arr.sort` invokes the old builtin array sorting which is terribly slow, whereas `import std.algorithm; arr.sort()` uses the much better sorting algorithm defined in Phobos.
Re: reading file byLine
On Sunday, 13 September 2015 at 03:20:31 UTC, deed wrote:
string s = "Some text";
s.retro.find("e"); // `Some te` (Surprising to me.
Error? 2.067.1)
Sorry, the above is wrong, .retro.find does indeed return what's
expected.
string s = "Some text";
s.retro.find("e").writeln; // Prints `et emoS`, as expected.
Re: reading file byLine
On Sunday, 13 September 2015 at 03:20:31 UTC, deed wrote: ... and since `string` is an alias for `const(char)[]`, it's not ... string is an alias for immutable(char)[], not const(char)[]. http://dlang.org/arrays.html#strings Sorry about the noise.
Re: reading file byLine
On Saturday, 12 September 2015 at 12:51:04 UTC, Namal wrote:
Anyway, there is no .reverse for strings I guess, what is the
way to completely reverse a string in D?
What do you want to do? Do you want to keep your data in original
order, but get a reversed view of it for something, or do you
actually want to reverse your original array?
You can use `retro` to simply read your array backwards, i.e.:
string s = "Some text";
s.retro.writeln; // `txet emoS`
s.writeln; // `Some text`
s.retro.find("e"); // `Some te` (Surprising to me. Error?
2.067.1)
s.retro.until("e").writeln;// `tx`
s.find("e"); // `Some`
The string is still kept in original order, but `retro` returns a
range reading the array backwards. If you want to store a
reversed string in memory, that's possible too, of course. One
way of doing it, is to convert your retro range to a string:
s = s.retro.to!string;
s.writeln; // `txet emoS`
This will allocate new memory for the reversed copy and assign it
to `s`.
Reverse is an algorithm that swaps values at different indices
and since `string` is an alias for `const(char)[]`, it's not
allowed. It means that each element of the array is const, so you
cannot mutate any elements, but you can append or remove elements
or assign the slice to view another part of the string or some
other string. Hence, a `s.reverse` will give you an error. If you
use `char[]` instead of `const(char)[]` you can use reverse and
reuse the same memory for the reversed `char[]`. To illustrate:
char[] t = ['a', 'b', 'c'];
std.algorithm.reverse(t);
t.writeln; // `cba`
// s[0] = s[$-1]; // Error, cannot mutate const elements
auto r = s.retro;
s.length = 0;
r.each!(e => s ~= e);
s.writeln; // s has the reversed string, obtained
through
// a temporary range object, setting
length to
// zero and appending the elements
from the
// range, which is allowed for
const(char)[]
Re: reading file byLine
On Monday, 7 September 2015 at 10:28:20 UTC, deed wrote: On Monday, 7 September 2015 at 10:25:09 UTC, deed wrote: writeln(x);// or you can pass it to a function. I meant `writeln(x + 5)` If I have just red your post before I started using reverse on dynamic arrays... Anyway, there is no .reverse for strings I guess, what is the way to completely reverse a string in D?
Re: reading file byLine
On Sunday, 6 September 2015 at 22:04:55 UTC, Namal wrote: oh, sorry. But I found out what I have been doing wrong besides that. arr.sort.uniq; uniq(arr) or arr.sort.uniq; compiles but doesn't store it in the arr array, I need to store it in a new one. Right, it's like int x = 3; // x + 5; // Just an expression evaluated to 8, // but what do you want to do with it? // It won't affect your program and the // compiler will give you an error. int y = x + 5; // But you can assign the expression to // a new variable x = x + 5; // or you can assign it back writeln(x);// or you can pass it to a function. // For your case: int[] arr = [1, 2, 3, 2, 1, 4]; arr.sort; // Operating on arr in place -> arr itself is mutated arr.writeln; // [1, 1, 2, 2, 3, 4] arr.uniq; // Not operating on arr, it's like the expression // x + 5 (but no compiler error is given). arr.uniq.writeln; // [1, 2, 3, 4] (Expression passed to writeln) arr.writeln; // [1, 1, 2, 2, 3, 4] (Not affected) int[] newArr = arr.uniq.array; // Expression put into a new array assigned to newArr newArr.writeln;// [1, 2, 3, 4] arr.writeln; // Still the sorted array. [1, 1, 2, 2, 3, 4] arr = arr.uniq.array; // Now arr is assigned the uniq array arr.writeln; // [1, 2, 3, 4] You need to know whether the function will mutate your array; sort does, while uniq doesn't. If you want to do things requiring mutation, but still want your original data unchanged, you can duplicate the data with .dup before the mutating operations, like this: int[] data = [1, 2, 2, 1]; int[] uniqData = data.dup.sort.uniq.array; data.writeln; // [1, 2, 2, 1] Unchanged, a duplicate was sorted. uniqData.writeln; // [1, 2]
Re: reading file byLine
On Monday, 7 September 2015 at 10:25:09 UTC, deed wrote: writeln(x);// or you can pass it to a function. I meant `writeln(x + 5)`
Re: reading file byLine
On Sunday, 6 September 2015 at 20:39:27 UTC, deed wrote:
On Sunday, 6 September 2015 at 17:57:49 UTC, Namal wrote:
Yeah, I just checked, it is 2.066, how can I install the new
version on ubuntu with sudo apt-get?
sudo apt-get install dmd
will give you dmd v2.067.1. Don't know when it will be upgraded
to 2.068 though.
I used the software center to install the newest one. Now it
compiles but I have no clue how to use uniq properly. I just tried
uniq(sort(arr));
and
auto arr = sort(a).uniq!("a==b").array;
but I don't get an array with unique elements.
Re: reading file byLine
That should be it though... Could you try this minimal complete
test?
import std.stdio;
import std.algorithm;
void main(string[] args) {
int[] arr = [1, 2, 4, 2, 3, 4, 1];
arr.sort.uniq.writeln;
}
// [1, 2, 3, 4]
yes, it works likte that.
unique(arr) I get
Error: undefined identifier 'unique', did you mean template
'uniq(alias pred = "a == b", Range)(Range r) if
(isInputRange!Range && is(typeof(binaryFun!pred(r.front,
r.front)) == bool))'?
Re: reading file byLine
Well, if you don't type function names right, it will be hard to help you. oh, sorry. But I found out what I have been doing wrong besides that. arr.sort.uniq; uniq(arr) or arr.sort.uniq; compiles but doesn't store it in the arr array, I need to store it in a new one.
Re: reading file byLine
On Sunday, 6 September 2015 at 21:01:09 UTC, Namal wrote:
On Sunday, 6 September 2015 at 20:39:27 UTC, deed wrote:
On Sunday, 6 September 2015 at 17:57:49 UTC, Namal wrote:
Yeah, I just checked, it is 2.066, how can I install the new
version on ubuntu with sudo apt-get?
sudo apt-get install dmd
will give you dmd v2.067.1. Don't know when it will be
upgraded to 2.068 though.
I used the software center to install the newest one. Now it
compiles but I have no clue how to use uniq properly. I just
tried
uniq(sort(arr));
and
auto arr = sort(a).uniq!("a==b").array;
but I don't get an array with unique elements.
That should be it though... Could you try this minimal complete
test?
import std.stdio;
import std.algorithm;
void main(string[] args) {
int[] arr = [1, 2, 4, 2, 3, 4, 1];
arr.sort.uniq.writeln;
}
// [1, 2, 3, 4]
Re: reading file byLine
On Sunday, 6 September 2015 at 21:18:28 UTC, Namal wrote:
That should be it though... Could you try this minimal
complete test?
import std.stdio;
import std.algorithm;
void main(string[] args) {
int[] arr = [1, 2, 4, 2, 3, 4, 1];
arr.sort.uniq.writeln;
}
// [1, 2, 3, 4]
yes, it works likte that.
unique(arr) I get
Error: undefined identifier 'unique', did you mean template
'uniq(alias pred = "a == b", Range)(Range r) if
(isInputRange!Range && is(typeof(binaryFun!pred(r.front,
r.front)) == bool))'?
Well, if you don't type function names right, it will be hard to
help you.
Re: reading file byLine
On Sunday, 6 September 2015 at 17:57:49 UTC, Namal wrote: Yeah, I just checked, it is 2.066, how can I install the new version on ubuntu with sudo apt-get? sudo apt-get install dmd will give you dmd v2.067.1. Don't know when it will be upgraded to 2.068 though.
Re: reading file byLine
Are you on 2.066 or older? Back then std.algorithm hasn't been split into submodules yet. Just import std.algorithm then instead of std.algorithm.comparison, std.algorithm.iteration, etc. Yeah, I just checked, it is 2.066, how can I install the new version on ubuntu with sudo apt-get? I don't realy want to mess with is manually. Also tried just to use algorithm and I get same error message.
Re: reading file byLine
On Sunday, 6 September 2015 at 15:41:34 UTC, Namal wrote: is there any function that removes double elements in a sorted array? std.algorithm.iteration.uniq http://dlang.org/phobos/std_algorithm_iteration.html#uniq
Re: reading file byLine
Note that there's a specialized `std.algorithm.iteration.sum`. is there any function that removes double elements in a sorted array?
Re: reading file byLine
On Sunday, 6 September 2015 at 15:52:38 UTC, anonymous wrote: On Sunday, 6 September 2015 at 15:41:34 UTC, Namal wrote: is there any function that removes double elements in a sorted array? std.algorithm.iteration.uniq http://dlang.org/phobos/std_algorithm_iteration.html#uniq Hmm, I get Error: module comparison is in file 'std/algorithm/comparison.d' which cannot be read import path[0] = /usr/include/dmd/phobos import path[1] = /usr/include/dmd/druntime/import when I try to load the headers like in the example
Re: reading file byLine
On Sunday, 6 September 2015 at 16:17:29 UTC, Namal wrote: Error: module comparison is in file 'std/algorithm/comparison.d' which cannot be read import path[0] = /usr/include/dmd/phobos import path[1] = /usr/include/dmd/druntime/import when I try to load the headers like in the example Are you on 2.066 or older? Back then std.algorithm hasn't been split into submodules yet. Just import std.algorithm then instead of std.algorithm.comparison, std.algorithm.iteration, etc.
Re: reading file byLine
On Saturday, 5 September 2015 at 18:57:52 UTC, deed wrote:
On Saturday, 5 September 2015 at 17:31:39 UTC, Namal wrote:
Yeah, I have have been trying this example from wiki books
https://en.wikibooks.org/wiki/Learning_D_With_Project_Euler
It is not even compiling.
What exactly is not compiling?
the last codesample on the bottom. I think because of the old D?
Index for the last array.length-1 is now $-1. But also I get
Error: undefined identifier 'file'
for the read line. But even when I fixed those errors the strings
I got were with those quotation marks and backslashes. However,
with your help I could solve it now.
I moved to the next problem and wrote the program for it
import std.stdio, std.algorithm, std.array;
bool abundant(int n){
int[] a;
foreach(i;1..n)
if(!(n%i))
a~=i;
auto sum = reduce!((a,b)=>a+b)(0,a);
return sum>n;
}
void main(){
long sum;
int[] arr;
int[28123] mark;
foreach(i;1..28124)
if(abundant(i))
arr~=i;
foreach(i;arr)
foreach(j;arr){
if(i+j>28123)
break;
mark[i+j-1] = 1;
}
for(auto i = 0;i
Re: reading file byLine
On Saturday, 5 September 2015 at 17:31:39 UTC, Namal wrote: Yeah, I have have been trying this example from wiki books https://en.wikibooks.org/wiki/Learning_D_With_Project_Euler It is not even compiling. What exactly is not compiling?
Re: reading file byLine
On Saturday, 5 September 2015 at 14:49:13 UTC, deed wrote: On Saturday, 5 September 2015 at 14:44:19 UTC, deed wrote: .map!(s => chomp(s, "\"") .map!(s => chompPrefix(s, "\"") should be .map!(s => chomp(s, "\"")) .map!(s => chompPrefix(s, "\"")) Yeah, I have have been trying this example from wiki books https://en.wikibooks.org/wiki/Learning_D_With_Project_Euler It is not even compiling.
Re: reading file byLine
On Saturday, 5 September 2015 at 12:41:37 UTC, Namal wrote:
Thx guys. Now I try out the split function. I read the file as
a single string?
auto arr = split(cast(string)read(filename),",");
where the file has "A", "B", "C"
and I get the output ["\"A\"", " \"B\"", " \"C\"\n"]
I can understand that read functions reads the endl but what
does it with the quotation marks? how can I modify read so I
get just ["A", "B", "C"]
'\' is the escape character and is used to disambiguate start or
end of string (") and a quotation mark within the string (\"),
the same way as "\n" means newline and not '\' 'n', which would
have been "\\n".
So what you have is [`"A"`, ` "B"`, ` "C"\n`], if you use ` for
start\stop of string. You say you want ["A", "B", "C"], so you
need to remove whitespace. You can do that with std.string.strip.
Assuming you also want to remove the quotation marks present in
the file, one solution is to use std.string.chomp and
std.string.chompPrefix, for example:
string s = cast(string) read(filename);
s.split(",")
.map!strip
.map!(s => chomp(s, "\"")
.map!(s => chompPrefix(s, "\"")
.writeln
;
Re: reading file byLine
On Friday, 4 September 2015 at 12:09:19 UTC, Edwin van Leeuwen
wrote:
On Friday, 4 September 2015 at 12:06:08 UTC, Edwin van Leeuwen
wrote:
On Friday, 4 September 2015 at 11:50:23 UTC, deed wrote:
import std.algorithm, std.range, std.array, std.string,
std.stdio,
std.conv;
int[] arr1 = [1, 2, 30];
//arr1.max.writeln; // Doesn't work, as you say
arr1.reduce!max.writeln;// This does. Prints 30.
Again using reduce is the functional way to do it. The above
basically boils down to:
int[] arr1 = [1, 2, 30];
int maxElement = arr1[1];
foreach( element; arr1[2..$] ) //2..$ is short hand for second
till last ($) element
{
maxElement = max( maxElement, element );
}
writeln( maxElement );
Sorry been using too much R, so my indexes are off by 1:
int[] arr1 = [1, 2, 30];
int maxElement = arr1[0];
foreach( element; arr1[1..$] ) //1..$ is short hand for second
till last ($) element
{
maxElement = max( maxElement, element );
}
writeln( maxElement );
Thx guys. Now I try out the split function. I read the file as a
single string?
auto arr = split(cast(string)read(filename),",");
where the file has "A", "B", "C"
and I get the output ["\"A\"", " \"B\"", " \"C\"\n"]
I can understand that read functions reads the endl but what does
it with the quotation marks? how can I modify read so I get just
["A", "B", "C"]
Re: reading file byLine
On Saturday, 5 September 2015 at 14:44:19 UTC, deed wrote: .map!(s => chomp(s, "\"") .map!(s => chompPrefix(s, "\"") should be .map!(s => chomp(s, "\"")) .map!(s => chompPrefix(s, "\""))
Re: reading file byLine
On Friday, 4 September 2015 at 07:27:54 UTC, Namal wrote:
On Friday, 4 September 2015 at 01:55:13 UTC, deed wrote:
On Friday, 4 September 2015 at 01:31:28 UTC, Namal wrote:
How can I get just the maximum element? Do I need to give a
range for it?
Use max?
http://dlang.org/phobos/std_algorithm_comparison.html#max
Sorry, I don't understand the syntax yet. How do I tell max to
search all elements?
You can search all elements by using reduce
http://dlang.org/phobos/std_algorithm_iteration.html#reduce
I mean, why does sort(myarray) is legit and max(myarray) isn't.
I don't know why, other than that is the current design in Phobos.
import std.algorithm, std.range, std.array, std.string, std.stdio,
std.conv;
int[] arr1 = [1, 2, 30];
//arr1.max.writeln; // Doesn't work, as you say
arr1.reduce!max.writeln;// This does. Prints 30.
int[] arr2 = [4, 5, 6];
int[][] arr = [arr1, arr2];
arr.reduce!max.writeln; // Returns either arr1 or arr2.
Element by
// element comparison until one is
greatest.
// Prints arr2, since 1 < 4.
arr.joiner.reduce!max.writeln; // Flattens arr1 and arr2 to one
arr and
// finds max. Prints 30.
//For your example:
auto f = File("filename", "r");
auto numbers = f// 1 2 3\n4 5 6
.byLine // ["1 2 3", "4 5 6"]
.map!(a => a.split) // [["1", "2", "3"], ["4", "5", "6"]]
.map!(a => a.to!(int[]))// [[1, 2, 3], [4, 5, 6]]
.array; // Allocates and puts the elements
into an
// int[][] for reuse of state.
numbers // [[1, 2, 3], [4, 5, 6]]
.map!(reduce!max) // [3, 6]
.writeln; // prints [3, 6]
numbers // [[1, 2, 3], [4, 5, 6]]
.joiner // [1, 2, 3, 4, 5, 6]
.reduce!max // 6
.writeln; // prints 6
Re: reading file byLine
On Friday, 4 September 2015 at 12:06:08 UTC, Edwin van Leeuwen
wrote:
On Friday, 4 September 2015 at 11:50:23 UTC, deed wrote:
import std.algorithm, std.range, std.array, std.string,
std.stdio,
std.conv;
int[] arr1 = [1, 2, 30];
//arr1.max.writeln; // Doesn't work, as you say
arr1.reduce!max.writeln;// This does. Prints 30.
Again using reduce is the functional way to do it. The above
basically boils down to:
int[] arr1 = [1, 2, 30];
int maxElement = arr1[1];
foreach( element; arr1[2..$] ) //2..$ is short hand for second
till last ($) element
{
maxElement = max( maxElement, element );
}
writeln( maxElement );
Sorry been using too much R, so my indexes are off by 1:
int[] arr1 = [1, 2, 30];
int maxElement = arr1[0];
foreach( element; arr1[1..$] ) //1..$ is short hand for second
till last ($) element
{
maxElement = max( maxElement, element );
}
writeln( maxElement );
Re: reading file byLine
On Friday, 4 September 2015 at 11:50:23 UTC, deed wrote:
import std.algorithm, std.range, std.array, std.string,
std.stdio,
std.conv;
int[] arr1 = [1, 2, 30];
//arr1.max.writeln; // Doesn't work, as you say
arr1.reduce!max.writeln;// This does. Prints 30.
Again using reduce is the functional way to do it. The above
basically boils down to:
int[] arr1 = [1, 2, 30];
int maxElement = arr1[1];
foreach( element; arr1[2..$] ) //2..$ is short hand for second
till last ($) element
{
maxElement = max( maxElement, element );
}
writeln( maxElement );
Re: reading file byLine
On Friday, 4 September 2015 at 01:55:13 UTC, deed wrote: On Friday, 4 September 2015 at 01:31:28 UTC, Namal wrote: How can I get just the maximum element? Do I need to give a range for it? Use max? http://dlang.org/phobos/std_algorithm_comparison.html#max Sorry, I don't understand the syntax yet. How do I tell max to search all elements? I mean, why does sort(myarray) is legit and max(myarray) isn't.
Re: reading file byLine
On Wednesday, 2 September 2015 at 22:19:11 UTC, wobbles wrote:
On Wednesday, 2 September 2015 at 21:53:20 UTC, Namal wrote:
Thx guys, this helped alot. The next thing I want to do is
read the file line by line and split the stream into words. I
found this example of code that seems to do sort of something
like it. How can I modyfy it so I can store the words in an
array of strings? Is a => a.length the iterator range?
import std.algorithm, std.stdio, std.string;
// Count words in a file using ranges.
void main()
{
auto file = File("file.txt"); // Open for reading
const wordCount = file.byLine()// Read lines
.map!split // Split into
words
.map!(a => a.length) // Count words
per line
.sum(); // Total word
count
writeln(wordCount);
}
I would do what you want like this
auto file = File("file.txt");
auto words = file.byLine() // you've all lines in
range
.map!(a => a.split); // read each line,
splitting it into words
// now you've a range,
where each element is an array of words
The map!(a => a.split) line simply maps each element to the
return value of a.split - this is the predicate.
The a => a.split syntax is a lambda expression that tells map
what to do on each element.
hello, just copy pasting this brought me those errors:
ep18.d(10): Error: no property 'split' for type 'char[]'
/usr/include/dmd/phobos/std/algorithm.d(427):instantiated
from here: MapResult!(__lambda1, ByLine!(char, char))
ep18.d(10):instantiated from here: map!(ByLine!(char,
char))
and then a long list to the end of my code
Error: undefined identifier a
Re: reading file byLine
On Thursday, 3 September 2015 at 22:48:01 UTC, Jordan Wilson wrote: On Thursday, 3 September 2015 at 22:21:57 UTC, Namal wrote: ep18.d(10): Error: no property 'split' for type 'char[]' /usr/include/dmd/phobos/std/algorithm.d(427): instantiated from here: MapResult!(__lambda1, ByLine!(char, char)) ep18.d(10):instantiated from here: map!(ByLine!(char, char)) and then a long list to the end of my code Error: undefined identifier a Hmm, seems I forgot to add std.string, now it works, but words seems not to be an array, at least I cannot access it like an array. words[0][0] leads to Error: no [] operator overload for type MapResult!(__lambda1, ByLine!(char, char)) So is is a map? How can I convert all the elements in it to integer and store it in a real array? I believe it's by using array: auto words = file.byLine() // you've all lines in range .map!(a => a.split).array(); Sorry, I didn't notice the "convert all the elements in it to integer" part. I think I saw reference to the to! before...that is one way to convert. auto words = file.byLine() // you've all lines in range .map!(a => a.split) .map!(a => to!int(a)).array();
Re: reading file byLine
Sorry, I didn't notice the "convert all the elements in it to
integer" part.
I think I saw reference to the to! before...that is one way to
convert.
auto words = file.byLine() // you've all lines in
range
.map!(a => a.split)
.map!(a => to!int(a)).array();
import std.file, std.stdio, std.string, std.conv;
void main(){
auto file = File("text.txt");
auto numbers = file.byLine()
.map!(a => a.split)
.map!(a => to!int(a)).array();
writeln(numbers);
}
ep18.d(7): Error: no property 'map' for type 'ByLine!(char, char)'
Re: reading file byLine
Actually, need an extra map I think: auto word = file.byLine() .map!(a => a.split) .map!(a => map!(a => to!int(a))(a)) .array();
Re: reading file byLine
On Fri, Sep 04, 2015 at 12:18:14AM +, Namal via Digitalmars-d-learn wrote: [...] > That being said, when do I have to import std.array and std.string? > Every time I use std.array? I can obviously use arrays and strings > without those libs. Arrays and strings are built into the language; but many common operations on arrays and strings are not built-in, but are provided in the standard library, i.e., std.array and std.string. So if you use just the plain ~, ~=, operators, then you don't need std.array or std.string. But if you need functions like split() or array(), then you need to import std.array. If you're only dealing with strings as char arrays, then that's all you need. But if you want some string-specific functions, e.g., isNumeric(), chomp(), capitalize(), etc., then you need std.string. Also, some of the more generic operations that can be applied to more than just arrays or strings, will be found in std.algorithm, such as map(), find(), count(), startsWith(), etc.. Basically, if an operation *only* applies to strings, it should generally be found in std.string; if it can also apply to arrays, then it should be found in std.array. If it can be applied to more than just arrays (that is, ranges, e.g., a file stream, a network socket, a sequence of values produced by a generating function, etc., anything with array-like sequential semantics that are not necessarily actual arrays), then it will generally be found in std.algorithm. One useful rule-of-thumb to decide where to look is to ask yourself if an operation on an array can also be logically applied to a linked-list. If it can, it's probably in std.algorithm. If not (i.e. it depends on semantics specific to arrays), then it's probably in std.array. Hope this helps. T -- Latin's a dead language, as dead as can be; it killed off all the Romans, and now it's killing me! -- Schoolboy
Re: reading file byLine
On Thursday, 3 September 2015 at 23:54:44 UTC, H. S. Teoh wrote:
On Thu, Sep 03, 2015 at 11:38:54PM +, Namal via
Digitalmars-d-learn wrote:
On Thursday, 3 September 2015 at 23:31:27 UTC, Jordan Wilson
wrote:
>On Thursday, 3 September 2015 at 23:28:37 UTC, Namal wrote:
>>On Thursday, 3 September 2015 at 23:25:52 UTC, Jordan Wilson
>>wrote:
>>>And also:
>>>import std.algorithm
>>>
>>>Sorry, I should have taken the time to answer properly and
>>>fully.
>>
>>import std.file, std.stdio, std.string, std.conv,
>>std.algorithm;
>>
>>void main(){
>>
>>auto file = File("text.txt");
>>auto numbers = file.byLine()
>> .map!(a => a.split)
>> .map!(a => map!(a => to!int(a))(a))
>> .array();
>>
>>writeln(numbers);
>>}
>>
>>Error: no property 'array' for type 'MapResult!(__lambda2,
>>MapResult!(__lambda1, ByLine!(char, char)))'
>>
>>Still an error.
>
>import std.array
Thx, finaly, this is so much harder to understand than c++
iostream
I would have written it slightly differently, to emphasize what
exactly is going on:
auto numbers = File("text.txt") // read file
.byLine() // line by line
.map!(a => a.split // split each line into words
.map!(a => to!int(a)) // convert each word into int
.array) // collect the ints into an array (per
line)
.array; // collect all line arrays into one big
array
This is the functional way of doing it, of course. If you're
more comfortable with the C++-style imperative approach, you
could do this instead:
auto file = File("text.txt");
int[][] numbers;
foreach (line; file.byLine) {
auto words = line.split;
int[] lineNums;
foreach (word; words) {
lineNums ~= word.to!int;
}
numbers ~= lineNums;
}
The functional approach is admittedly a bit harder to
understand at first, but it's extremely powerful because it
processes everything in a pipeline, and you can compose
operators on the pipeline easily, rearrange the sequence of
operations, etc..
In the imperative nested-loop approach, things quickly get out
of hand once the loop is nested about 2-3 levels deep. A nested
loop of 6-7 levels deep would be basically impossible to
understand, maintain, or debug without major refactoring into
smaller functions. (In fact, split() is a library-provided
function that basically encapsulates one of those nested
loops.) But if you take the refactoring to its logical
conclusion, you'll eventually end up with a whole bunch of tiny
functions with only a single loop each, each calling the next
function in a chain -- in other words, you arrive at the
functional pipeline approach. :-)
D allows you to do it either way, but the superior approach IMO
is to learn the functional pipeline approach.
T
Thx Theo, this and the lack of foolproof tutorials were the
reason why I gave up on D 2 years ago and went instead to C++.
But I am not giving up this time. That being said, when do I have
to import std.array and std.string? Every time I use std.array? I
can obviously use arrays and strings without those libs.
Re: reading file byLine
On Thursday, 3 September 2015 at 22:21:57 UTC, Namal wrote: ep18.d(10): Error: no property 'split' for type 'char[]' /usr/include/dmd/phobos/std/algorithm.d(427): instantiated from here: MapResult!(__lambda1, ByLine!(char, char)) ep18.d(10):instantiated from here: map!(ByLine!(char, char)) and then a long list to the end of my code Error: undefined identifier a Hmm, seems I forgot to add std.string, now it works, but words seems not to be an array, at least I cannot access it like an array. words[0][0] leads to Error: no [] operator overload for type MapResult!(__lambda1, ByLine!(char, char)) So is is a map? How can I convert all the elements in it to integer and store it in a real array? I believe it's by using array: auto words = file.byLine() // you've all lines in range .map!(a => a.split).array();
Re: reading file byLine
On Thursday, 3 September 2015 at 23:31:27 UTC, Jordan Wilson
wrote:
On Thursday, 3 September 2015 at 23:28:37 UTC, Namal wrote:
On Thursday, 3 September 2015 at 23:25:52 UTC, Jordan Wilson
wrote:
And also:
import std.algorithm
Sorry, I should have taken the time to answer properly and
fully.
import std.file, std.stdio, std.string, std.conv,
std.algorithm;
void main(){
auto file = File("text.txt");
auto numbers = file.byLine()
.map!(a => a.split)
.map!(a => map!(a => to!int(a))(a))
.array();
writeln(numbers);
}
Error: no property 'array' for type 'MapResult!(__lambda2,
MapResult!(__lambda1, ByLine!(char, char)))'
Still an error.
import std.array
Thx, finaly, this is so much harder to understand than c++
iostream
Re: reading file byLine
On Thu, Sep 03, 2015 at 11:38:54PM +, Namal via Digitalmars-d-learn wrote:
> On Thursday, 3 September 2015 at 23:31:27 UTC, Jordan Wilson wrote:
> >On Thursday, 3 September 2015 at 23:28:37 UTC, Namal wrote:
> >>On Thursday, 3 September 2015 at 23:25:52 UTC, Jordan Wilson wrote:
> >>>And also:
> >>>import std.algorithm
> >>>
> >>>Sorry, I should have taken the time to answer properly and fully.
> >>
> >>import std.file, std.stdio, std.string, std.conv, std.algorithm;
> >>
> >>void main(){
> >>
> >>auto file = File("text.txt");
> >>auto numbers = file.byLine()
> >> .map!(a => a.split)
> >> .map!(a => map!(a => to!int(a))(a))
> >> .array();
> >>
> >>writeln(numbers);
> >>}
> >>
> >>Error: no property 'array' for type 'MapResult!(__lambda2,
> >>MapResult!(__lambda1, ByLine!(char, char)))'
> >>
> >>Still an error.
> >
> >import std.array
>
> Thx, finaly, this is so much harder to understand than c++ iostream
I would have written it slightly differently, to emphasize what exactly
is going on:
auto numbers = File("text.txt") // read file
.byLine() // line by line
.map!(a => a.split // split each line into words
.map!(a => to!int(a)) // convert each word into int
.array) // collect the ints into an array (per
line)
.array; // collect all line arrays into one big
array
This is the functional way of doing it, of course. If you're more
comfortable with the C++-style imperative approach, you could do this
instead:
auto file = File("text.txt");
int[][] numbers;
foreach (line; file.byLine) {
auto words = line.split;
int[] lineNums;
foreach (word; words) {
lineNums ~= word.to!int;
}
numbers ~= lineNums;
}
The functional approach is admittedly a bit harder to understand at
first, but it's extremely powerful because it processes everything in a
pipeline, and you can compose operators on the pipeline easily,
rearrange the sequence of operations, etc..
In the imperative nested-loop approach, things quickly get out of hand
once the loop is nested about 2-3 levels deep. A nested loop of 6-7
levels deep would be basically impossible to understand, maintain, or
debug without major refactoring into smaller functions. (In fact,
split() is a library-provided function that basically encapsulates one
of those nested loops.) But if you take the refactoring to its logical
conclusion, you'll eventually end up with a whole bunch of tiny
functions with only a single loop each, each calling the next function
in a chain -- in other words, you arrive at the functional pipeline
approach. :-)
D allows you to do it either way, but the superior approach IMO is to
learn the functional pipeline approach.
T
--
Life is too short to run proprietary software. -- Bdale Garbee
Re: reading file byLine
ep18.d(10): Error: no property 'split' for type 'char[]' /usr/include/dmd/phobos/std/algorithm.d(427): instantiated from here: MapResult!(__lambda1, ByLine!(char, char)) ep18.d(10):instantiated from here: map!(ByLine!(char, char)) and then a long list to the end of my code Error: undefined identifier a Hmm, seems I forgot to add std.string, now it works, but words seems not to be an array, at least I cannot access it like an array. words[0][0] leads to Error: no [] operator overload for type MapResult!(__lambda1, ByLine!(char, char)) So is is a map? How can I convert all the elements in it to integer and store it in a real array?
Re: reading file byLine
On Thursday, 3 September 2015 at 23:25:52 UTC, Jordan Wilson
wrote:
And also:
import std.algorithm
Sorry, I should have taken the time to answer properly and
fully.
import std.file, std.stdio, std.string, std.conv, std.algorithm;
void main(){
auto file = File("text.txt");
auto numbers = file.byLine()
.map!(a => a.split)
.map!(a => map!(a => to!int(a))(a))
.array();
writeln(numbers);
}
Error: no property 'array' for type 'MapResult!(__lambda2,
MapResult!(__lambda1, ByLine!(char, char)))'
Still an error.
Re: reading file byLine
And also: import std.algorithm Sorry, I should have taken the time to answer properly and fully.
Re: reading file byLine
On Thursday, 3 September 2015 at 23:28:37 UTC, Namal wrote:
On Thursday, 3 September 2015 at 23:25:52 UTC, Jordan Wilson
wrote:
And also:
import std.algorithm
Sorry, I should have taken the time to answer properly and
fully.
import std.file, std.stdio, std.string, std.conv, std.algorithm;
void main(){
auto file = File("text.txt");
auto numbers = file.byLine()
.map!(a => a.split)
.map!(a => map!(a => to!int(a))(a))
.array();
writeln(numbers);
}
Error: no property 'array' for type 'MapResult!(__lambda2,
MapResult!(__lambda1, ByLine!(char, char)))'
Still an error.
import std.array
Re: reading file byLine
On Thu, Sep 03, 2015 at 11:22:09PM +, Namal via Digitalmars-d-learn wrote:
> >Sorry, I didn't notice the "convert all the elements in it to integer"
> >part.
> >I think I saw reference to the to! before...that is one way to convert.
> >
> >auto words = file.byLine() // you've all lines in range
> > .map!(a => a.split)
> >.map!(a => to!int(a)).array();
>
>
> import std.file, std.stdio, std.string, std.conv;
>
> void main(){
>
> auto file = File("text.txt");
> auto numbers = file.byLine()
>.map!(a => a.split)
>.map!(a => to!int(a)).array();
>
> writeln(numbers);
> }
>
> ep18.d(7): Error: no property 'map' for type 'ByLine!(char, char)'
import std.algorithm : map;
T
--
Never step over a puddle, always step around it. Chances are that whatever made
it is still dripping.
Re: reading file byLine
On Thu, Sep 03, 2015 at 11:28:36PM +, Namal via Digitalmars-d-learn wrote:
> On Thursday, 3 September 2015 at 23:25:52 UTC, Jordan Wilson wrote:
> >And also:
> >import std.algorithm
> >
> >Sorry, I should have taken the time to answer properly and fully.
>
> import std.file, std.stdio, std.string, std.conv, std.algorithm;
>
> void main(){
>
> auto file = File("text.txt");
> auto numbers = file.byLine()
> .map!(a => a.split)
> .map!(a => map!(a => to!int(a))(a))
> .array();
>
> writeln(numbers);
> }
>
> Error: no property 'array' for type 'MapResult!(__lambda2,
> MapResult!(__lambda1, ByLine!(char, char)))'
>
> Still an error.
import std.array : array;
T
--
Do not reason with the unreasonable; you lose by definition.
Re: reading file byLine
On Friday, 4 September 2015 at 00:18:15 UTC, Namal wrote: On Thursday, 3 September 2015 at 23:54:44 UTC, H. S. Teoh wrote: [...] Thx Theo, this and the lack of foolproof tutorials were the reason why I gave up on D 2 years ago and went instead to C++. But I am not giving up this time. That being said, when do I have to import std.array and std.string? Every time I use std.array? I can obviously use arrays and strings without those libs. My 2 cents, as someone who is newish to D, I'd also recommend the above approach. I found the whole ranges thing to be hard to get at first, but I do find myself using ranges + std.algorithm more and more (even though it's mostly just basic map and filter).
Re: reading file byLine
On Friday, 4 September 2015 at 01:31:28 UTC, Namal wrote: How can I get just the maximum element? Do I need to give a range for it? Use max? http://dlang.org/phobos/std_algorithm_comparison.html#max
Re: reading file byLine
Hope this helps. Yes, it does. I have a question about arrays. I can sort an array A by sort(A); How can I get just the maximum element? Do I need to give a range for it?
Re: reading file byLine
On Wednesday, 2 September 2015 at 15:04:10 UTC, cym13 wrote:
On Wednesday, 2 September 2015 at 13:46:54 UTC, Namal wrote:
Thx, cym. I have a question about a D strings though. In c++ I
would just reuse the string buffer with the "=" how can I
clear the string after i store a line in the buffer and do
something with it. I also tried to append a line to an array
of strings but it failed because the line is a char?
In D you can do as in C++:
buffer = ""; // or a brand new string
You can also reset a variable to its initial state (what you
would hav had if you hadn't initialized it) using:
buffer.init();
When reading files the default type you get is dchar[]. There
are different kind of strings in D, you way want to check
http://dlang.org/arrays.html#strings . If you want to append to
an array of strings, simply convert your line to type string:
import std.conv;
import std.stdio;
void main() {
string[] buffer;
foreach (line ; File("test.txt").byLine)
buffer ~= line.to!string; // <- Here is the magic
writeln(buffer);
}
Actually, even if converting works, what qznc did is better in
the case of file reading. And even better would be to use
.byLineCopy which basically does the same thing as qznc's
solution but more efficiently:
import std.stdio;
void main() {
string[] buffer;
foreach (line ; File("test.txt").byLineCopy)
buffer ~= line;
writeln(buffer);
}
Re: reading file byLine
On Wednesday, 2 September 2015 at 15:04:10 UTC, cym13 wrote: You can also reset a variable to its initial state (what you would hav had if you hadn't initialized it) using: buffer.init(); Huh? That doesn't work... Instead, use: buffer = buffer.init;
Re: reading file byLine
Thx guys, this helped alot. The next thing I want to do is read
the file line by line and split the stream into words. I found
this example of code that seems to do sort of something like it.
How can I modyfy it so I can store the words in an array of
strings? Is a => a.length the iterator range?
import std.algorithm, std.stdio, std.string;
// Count words in a file using ranges.
void main()
{
auto file = File("file.txt"); // Open for reading
const wordCount = file.byLine()// Read lines
.map!split // Split into words
.map!(a => a.length) // Count words per
line
.sum(); // Total word count
writeln(wordCount);
}
Re: reading file byLine
On Wednesday, 2 September 2015 at 21:53:20 UTC, Namal wrote:
Thx guys, this helped alot. The next thing I want to do is read
the file line by line and split the stream into words. I found
this example of code that seems to do sort of something like
it. How can I modyfy it so I can store the words in an array of
strings? Is a => a.length the iterator range?
import std.algorithm, std.stdio, std.string;
// Count words in a file using ranges.
void main()
{
auto file = File("file.txt"); // Open for reading
const wordCount = file.byLine()// Read lines
.map!split // Split into
words
.map!(a => a.length) // Count words
per line
.sum(); // Total word
count
writeln(wordCount);
}
I would do what you want like this
auto file = File("file.txt");
auto words = file.byLine() // you've all lines in range
.map!(a => a.split); // read each line,
splitting it into words
// now you've a range, where
each element is an array of words
The map!(a => a.split) line simply maps each element to the
return value of a.split - this is the predicate.
The a => a.split syntax is a lambda expression that tells map
what to do on each element.
Re: reading file byLine
On Wednesday, 2 September 2015 at 13:12:39 UTC, cym13 wrote:
On Wednesday, 2 September 2015 at 13:01:31 UTC, Namal wrote:
Hello,
I want to read a file line by line and store each line in a
string. I found this example with byLine and ranges. First of
all, do I need the range lib at all to do this and if so what
is the range of the end of the file?
You don't need the range lib at all, std.range provides
advanced functions to work with ranges but ranges are a general
concept. You need std.stdio though as this is doing file
operations.
A way to do it is:
void main() {
auto f = File("myfile");
string buffer;
foreach (line ; f.byLine) {
buffer ~= line;
}
f.close();
writeln(buffer);
}
Note that by default byLine doesn't keep the line terminator.
See http://dlang.org/phobos/std_stdio.html#.File.byLine for
more informations.
Thx, cym. I have a question about a D strings though. In c++ I
would just reuse the string buffer with the "=" how can I clear
the string after i store a line in the buffer and do something
with it. I also tried to append a line to an array of strings but
it failed because the line is a char?
Re: reading file byLine
On Wednesday, 2 September 2015 at 13:01:31 UTC, Namal wrote:
Hello,
I want to read a file line by line and store each line in a
string. I found this example with byLine and ranges. First of
all, do I need the range lib at all to do this and if so what
is the range of the end of the file?
You don't need the range lib at all, std.range provides advanced
functions to work with ranges but ranges are a general concept.
You need std.stdio though as this is doing file operations.
A way to do it is:
void main() {
auto f = File("myfile");
string buffer;
foreach (line ; f.byLine) {
buffer ~= line;
}
f.close();
writeln(buffer);
}
Note that by default byLine doesn't keep the line terminator. See
http://dlang.org/phobos/std_stdio.html#.File.byLine for more
informations.
Re: reading file byLine
On Wednesday, 2 September 2015 at 13:46:54 UTC, Namal wrote:
On Wednesday, 2 September 2015 at 13:12:39 UTC, cym13 wrote:
On Wednesday, 2 September 2015 at 13:01:31 UTC, Namal wrote:
Hello,
I want to read a file line by line and store each line in a
string. I found this example with byLine and ranges. First of
all, do I need the range lib at all to do this and if so what
is the range of the end of the file?
You don't need the range lib at all, std.range provides
advanced functions to work with ranges but ranges are a
general concept. You need std.stdio though as this is doing
file operations.
A way to do it is:
void main() {
auto f = File("myfile");
string buffer;
foreach (line ; f.byLine) {
buffer ~= line;
}
f.close();
writeln(buffer);
}
Note that by default byLine doesn't keep the line terminator.
See http://dlang.org/phobos/std_stdio.html#.File.byLine for
more informations.
Thx, cym. I have a question about a D strings though. In c++ I
would just reuse the string buffer with the "=" how can I clear
the string after i store a line in the buffer and do something
with it.
Just like in C++: buffer = line;
However, you can just use "line" instead of "buffer" then. The
byLine does buffer internally, so it overwrites "line" on the
next iteration of foreach. If you want to keep the line string,
then make a copy "line.idup".
I also tried to append a line to an array of strings but it
failed because the line is a char?
Here is how to get an array of lines:
import std.stdio;
void main() {
auto f = File("myfile");
string buffer[];
foreach (line ; f.byLine) {
buffer ~= line.idup;
}
f.close();
writeln(buffer);
}
Re: reading file byLine
On Wednesday, 2 September 2015 at 13:46:54 UTC, Namal wrote:
Thx, cym. I have a question about a D strings though. In c++ I
would just reuse the string buffer with the "=" how can I clear
the string after i store a line in the buffer and do something
with it. I also tried to append a line to an array of strings
but it failed because the line is a char?
In D you can do as in C++:
buffer = ""; // or a brand new string
You can also reset a variable to its initial state (what you
would hav had if you hadn't initialized it) using:
buffer.init();
When reading files the default type you get is dchar[]. There are
different kind of strings in D, you way want to check
http://dlang.org/arrays.html#strings . If you want to append to
an array of strings, simply convert your line to type string:
import std.conv;
import std.stdio;
void main() {
string[] buffer;
foreach (line ; File("test.txt").byLine)
buffer ~= line.to!string; // <- Here is the magic
writeln(buffer);
}
