Re: Checking template parameter types of class
On 05/24/2015 09:14 PM, tcak wrote: Line 243: auto fileResourceList = new shared FileResourceList( 2 ); main.d(243): Error: class main.FileResourceList(T) if (is(T : FileResource)) is used as a type struct and class templates do not have automatic type deduction; function templates do. The solution is to provide a convenience function template alongside the struct or class. auto fileResourceList = new shared FileResourceList!FileResource( 2 ); Then it works. The error message is not indicating directly this, though logically it is still correct. 'if (is(T : FileResource))' part means if T can implicitly be converted to FileResource. You still provide T so that it gets checked. Ali
Re: Checking template parameter types of class
On Monday, 25 May 2015 at 04:15:00 UTC, tcak wrote: main.d(243): Error: class main.FileResourceList(T) if (is(T : FileResource)) is used as a type The error message is not indicating directly this, though logically it is still correct. Compiler means template is used as a type which is an error since templates are not types. I guess adding the word template to that message would make it more clear.
Re: Idiomatic way to call base method in generic code
On Sun, 24 May 2015 23:32:50 +, ZombineDev wrote:
I know I can call a base implementation of a method like in 3), but I
need to do it generically like in 2). Does anybody now how I can achieve
this?
i don't know why you want that, but something like this may do:
auto callBaseMethod(string MTN, C, Args...) (inout C self, Args args) {
alias FSC = BaseClassesTuple!(C)[0];
return mixin(`self.`~FSC.stringof~`.`~MTN~(args));
}
writeln(d.callBaseMethod!toString);
Additionally is there a way to make 1) work without using string mixins?
no. and again, why do you want that? why do you people are so afraid of
string mixins? ;-)
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Re: Idiomatic way to call base method in generic code
On Monday, 25 May 2015 at 07:57:49 UTC, ketmar wrote:
i don't know why you want that, but something like this may do:
auto callBaseMethod(string MTN, C, Args...) (inout C self, Args
args) {
alias FSC = BaseClassesTuple!(C)[0];
return mixin(`self.`~FSC.stringof~`.`~MTN~(args));
}
writeln(d.callBaseMethod!toString);
Thanks!
[1]:
https://github.com/ZombineDev/Chess2RT/blob/c36ba3e73744cf3912c25abccedbbd742f7f5be3/source/util/prettyprint.d#L7
[2]:
https://github.com/ZombineDev/Chess2RT/blob/master/source/util/prettyprint.d#L14
I initially had [1] a string mixin which goes through all the
members of a class and prints them and also prints its base
class' members, but then it seemed that it would be more cleaner
if I could use a function template [2] (which also improved my
debug experience) so I started exploring alias, but they turned
out to be less powerful then I thought:
alias can't refer to a nested member:
-
struct Point2
{
float x;
float y;
}
struct Line2
{
Point2 start;
Point2 end;
mixin Access;
// alias x1 = this.start.x; - this doesn't work :(
alias x1 = get!start.x;
alias y1 = get!start.y;
alias x2 = get!end.x;
alias y2 = get!end.y;
}
// I need to use a mixin to flatten the access :(
private mixin template Access()
{
ref auto get(string accessPattern)() inout
{
return mixin(accessPattern);
}
}
-
So I wondered if I'm missing something and decided to ask here.
no. and again, why do you want that? why do you people are so
afraid of
string mixins? ;-)
Well I'm not afraid of string mixins, but the `alias` keyword
seemed to possess some mysterious power (I was also under the
influence of this [3] blog post) which I wanted to explore. Also
they're a bit more elegant.
[3]:
http://blog.thecybershadow.net/2015/04/28/the-amazing-template-that-does-nothing/
Regex-Fu
I'm a bit at a loss here. I cannot get the longest possible
match. I tried several versions with eager operators and stuff,
but D's regex engine(s) always seem to return the shortest match.
Is there something embarrassingly simple I'm missing?
void main()
{
import std.regex : regex, matchFirst;
import std.stdio : writeln;
auto word = blablahula;
auto m = matchFirst(word, regex(^([a-z]+)(hula|ula)$));
writeln(m); // prints [blablahula, blablah, ula]
}
I want it to return hula not ula.
Re: Regex-Fu
I cannot get the longest possible it match longest for first group ([a-z]+) try ^([a-z]+?)(hula|ula)$
Re: Regex-Fu
On Monday, 25 May 2015 at 11:20:46 UTC, novice2 wrote: I cannot get the longest possible it match longest for first group ([a-z]+) try ^([a-z]+?)(hula|ula)$ Namespace, novice2: Ah, I see. The problem was with the first group that was too greedy, not with the second. I was focusing on the latter. Thanks, this works now!
Re: Regex-Fu
On Monday, 25 May 2015 at 11:11:50 UTC, Chris wrote:
I'm a bit at a loss here. I cannot get the longest possible
match. I tried several versions with eager operators and stuff,
but D's regex engine(s) always seem to return the shortest
match. Is there something embarrassingly simple I'm missing?
void main()
{
import std.regex : regex, matchFirst;
import std.stdio : writeln;
auto word = blablahula;
auto m = matchFirst(word, regex(^([a-z]+)(hula|ula)$));
writeln(m); // prints [blablahula, blablah, ula]
}
I want it to return hula not ula.
Make the + operator less greedy:
matchFirst(word, regex(^([a-z]+?)(hula|ula)$));
Re: Idiomatic way to call base method in generic code
On Monday, 25 May 2015 at 09:24:58 UTC, ZombineDev wrote:
On Monday, 25 May 2015 at 07:57:49 UTC, ketmar wrote:
i don't know why you want that, but something like this may do:
auto callBaseMethod(string MTN, C, Args...) (inout C self,
Args args) {
alias FSC = BaseClassesTuple!(C)[0];
return mixin(`self.`~FSC.stringof~`.`~MTN~(args));
}
writeln(d.callBaseMethod!toString);
Thanks!
[1]:
https://github.com/ZombineDev/Chess2RT/blob/c36ba3e73744cf3912c25abccedbbd742f7f5be3/source/util/prettyprint.d#L7
[2]:
https://github.com/ZombineDev/Chess2RT/blob/master/source/util/prettyprint.d#L14
I initially had [1] a string mixin which goes through all the
members of a class and prints them and also prints its base
class' members, but then it seemed that it would be more
cleaner if I could use a function template [2] (which also
improved my debug experience) so I started exploring alias, but
they turned out to be less powerful then I thought:
alias can't refer to a nested member:
-
struct Point2
{
float x;
float y;
}
struct Line2
{
Point2 start;
Point2 end;
mixin Access;
// alias x1 = this.start.x; - this doesn't work :(
alias x1 = get!start.x;
alias y1 = get!start.y;
alias x2 = get!end.x;
alias y2 = get!end.y;
}
// I need to use a mixin to flatten the access :(
private mixin template Access()
{
ref auto get(string accessPattern)() inout
{
return mixin(accessPattern);
}
}
-
So I wondered if I'm missing something and decided to ask here.
no. and again, why do you want that? why do you people are so
afraid of
string mixins? ;-)
Well I'm not afraid of string mixins, but the `alias` keyword
seemed to possess some mysterious power (I was also under the
influence of this [3] blog post) which I wanted to explore.
Also they're a bit more elegant.
[3]:
http://blog.thecybershadow.net/2015/04/28/the-amazing-template-that-does-nothing/
You might be interested in this thread:
http://forum.dlang.org/thread/mi3pip$22va$1...@digitalmars.com
Re: Replacing nested loops foreach using map/each/etc
On Monday, 25 May 2015 at 15:46:54 UTC, Dennis Ritchie wrote:
On Monday, 25 May 2015 at 15:06:45 UTC, Alex Parrill wrote:
Hint: Use `cartesianProduct` [1] with three iota ranges to
replace the foreachs, and `filter` to replace the if
[1]
http://dlang.org/phobos/std_algorithm_setops.html#.cartesianProduct
Thank you. Is it possible to replace the loop `foreach`
function `each` or `chunkBy` with the auxiliary functions?
import std.stdio, std.algorithm, std.range;
void main() {
const x = 12, y = 65, z = 50, s = 1435;
auto a = iota(0, x + 1);
foreach (idx; cartesianProduct(a, a, a).filter!(i = i[0] *
(y + 3 * z) + i[1] * (y + 2 * z) + i[2] * (y + z) == s)) {
writeln(idx[0] + idx[1] + idx[2]);
writeln(idx[0] * 3 + idx[1] * 2 + idx[2]);
writeln(idx[0] * 3 + idx[1] * 2 + idx[2]);
writeln(idx[0], idx[1], idx[2]);
}
}
-
http://rextester.com/HZP96719
import std.algorithm;
import std.range;
import std.stdio;
void main()
{
const x = 12, y = 65, z = 50, s = 1435;
auto a = iota(0, x + 1);
cartesianProduct(a, a, a)
.filter!(i = i[0] * (y + 3 * z)
+ i[1] * (y + 2 * z)
+ i[2] * (y + z)
== s)
.each!((idx)
{
writeln(idx[0] + idx[1] + idx[2]);
writeln(idx[0] * 3 + idx[1] * 2 + idx[2]);
writeln(idx[0] * 3 + idx[1] * 2 + idx[2]);
writeln(idx[0], idx[1], idx[2]);
});
}
Replacing nested loops foreach using map/each/etc
Hi,
Is it possible to write such a construction that could push
immediately to a conditional statement without using nested
loops? Ie organize search directly in the iterator if provided by
a map / each / iota and other support functions.
Ie I want to write this code shorter :)
import std.stdio;
void main() {
const x = 12, y = 65, z = 50, s = 1435;
foreach (i; 0 .. x + 1)
foreach (j; 0 .. x + 1)
foreach (k; 0 .. x + 1)
if (i * (y + 3 * z) + j * (y + 2 * z) + k * (y +
z) == s) {
writeln(i + j + k);
writeln(i * 3 + j * 2 + k);
writeln(i * 3 + j * 2 + k);
writeln(i, j, k);
}
}
-
http://rextester.com/SJTU87854
Re: Replacing nested loops foreach using map/each/etc
On Monday, 25 May 2015 at 15:06:45 UTC, Alex Parrill wrote:
Hint: Use `cartesianProduct` [1] with three iota ranges to
replace the foreachs, and `filter` to replace the if
[1]
http://dlang.org/phobos/std_algorithm_setops.html#.cartesianProduct
Thank you. Is it possible to replace the loop `foreach` function
`each` or `chunkBy` with the auxiliary functions?
import std.stdio, std.algorithm, std.range;
void main() {
const x = 12, y = 65, z = 50, s = 1435;
auto a = iota(0, x + 1);
foreach (idx; cartesianProduct(a, a, a).filter!(i = i[0] *
(y + 3 * z) + i[1] * (y + 2 * z) + i[2] * (y + z) == s)) {
writeln(idx[0] + idx[1] + idx[2]);
writeln(idx[0] * 3 + idx[1] * 2 + idx[2]);
writeln(idx[0] * 3 + idx[1] * 2 + idx[2]);
writeln(idx[0], idx[1], idx[2]);
}
}
-
http://rextester.com/HZP96719
Re: Replacing nested loops foreach using map/each/etc
On Monday, 25 May 2015 at 14:25:52 UTC, Dennis Ritchie wrote:
Hi,
Is it possible to write such a construction that could push
immediately to a conditional statement without using nested
loops? Ie organize search directly in the iterator if provided
by a map / each / iota and other support functions.
Ie I want to write this code shorter :)
import std.stdio;
void main() {
const x = 12, y = 65, z = 50, s = 1435;
foreach (i; 0 .. x + 1)
foreach (j; 0 .. x + 1)
foreach (k; 0 .. x + 1)
if (i * (y + 3 * z) + j * (y + 2 * z) + k * (y
+ z) == s) {
writeln(i + j + k);
writeln(i * 3 + j * 2 + k);
writeln(i * 3 + j * 2 + k);
writeln(i, j, k);
}
}
-
http://rextester.com/SJTU87854
Hint: Use `cartesianProduct` [1] with three iota ranges to
replace the foreachs, and `filter` to replace the if
[1]
http://dlang.org/phobos/std_algorithm_setops.html#.cartesianProduct
Re: Replacing nested loops foreach using map/each/etc
On Monday, 25 May 2015 at 16:41:35 UTC, Meta wrote:
import std.algorithm;
import std.range;
import std.stdio;
void main()
{
const x = 12, y = 65, z = 50, s = 1435;
auto a = iota(0, x + 1);
cartesianProduct(a, a, a)
.filter!(i = i[0] * (y + 3 * z)
+ i[1] * (y + 2 * z)
+ i[2] * (y + z)
== s)
.each!((idx)
{
writeln(idx[0] + idx[1] + idx[2]);
writeln(idx[0] * 3 + idx[1] * 2 + idx[2]);
writeln(idx[0] * 3 + idx[1] * 2 + idx[2]);
writeln(idx[0], idx[1], idx[2]);
});
}
Thanks. I do not even know what `each` support braces.
Re: How to append range to array?
On Saturday, 23 May 2015 at 07:03:35 UTC, Vladimir Panteleev
wrote:
int[] arr = [1, 2, 3];
auto r = iota(4, 10);
// ???
assert(equal(arr, iota(1, 10)));
Hopefully in one GC allocation (assuming we know the range's
length).
I tried std.range.primitives.put but its behavior seems a
little mysterious:
This compiles but asserts at runtime:
int[] arr = [1, 2, 3];
arr.put(iota(4, 10));
And this is even weirder, can you guess what it will print?
int[] arr = [1, 2, 3];
arr.put(4);
writeln(arr);
int[] arr = [1,2,3];
auto r = iota(4, 10);
auto app = arr.refAppender;
app.put(r);
assert(equal(arr, iota(1, 10)));
which of course you wrap with something like
auto append(T, R)(ref T arr, R r)
if(is(T : Q[], Q) isInputRange!r);
{
auto app = arr.refAppender;
app.put(r);
return arr;
}
to get
int[] arr = [1,2,3];
auto r = iota(4, 10);
arr.append(r);
assert(equal(arr, iota(1, 10)));
Walter has mentioned that he was interested in adding more
range-awareness to the language, so who knows, maybe this sort of
thing will get sugar at some point.
Re: Replacing nested loops foreach using map/each/etc
On Monday, 25 May 2015 at 17:05:35 UTC, Dennis Ritchie wrote:
On Monday, 25 May 2015 at 16:41:35 UTC, Meta wrote:
import std.algorithm;
import std.range;
import std.stdio;
void main()
{
const x = 12, y = 65, z = 50, s = 1435;
auto a = iota(0, x + 1);
cartesianProduct(a, a, a)
.filter!(i = i[0] * (y + 3 * z)
+ i[1] * (y + 2 * z)
+ i[2] * (y + z)
== s)
.each!((idx)
{
writeln(idx[0] + idx[1] + idx[2]);
writeln(idx[0] * 3 + idx[1] * 2 + idx[2]);
writeln(idx[0] * 3 + idx[1] * 2 + idx[2]);
writeln(idx[0], idx[1], idx[2]);
});
}
Thanks. I do not even know what `each` support braces.
`each` doesn't support braces. There are 4 ways to write a
function/delegate literal in D (with a few minor variations):
Short form:
function(int i) = i;
(int i) = i
(i) = i
i = i
Long form:
function(int i) { return i; }
(int i) { return i; }
(i) { return i; }
{ return 0; }
http://dlang.org/expression.html#FunctionLiteral
function
Re: Replacing nested loops foreach using map/each/etc
On Monday, 25 May 2015 at 19:16:04 UTC, anonymous wrote:
On Monday, 25 May 2015 at 17:52:09 UTC, Dennis Ritchie wrote:
But why is the solution breaks down when `s = 1` ? :)
import std.stdio, std.algorithm, std.range;
int c;
const x = 12, y = 65, z = 50, s = 10;
Which is it, now? 4 or 5 zeros?
No difference!
void solve(Range)(Range r) {
cartesianProduct(r, r, r).filter!(i = i[0] * (y + 3 * z) +
i[1] * (y + 2 * z) + i[2] * (y + z) == s).each!dout;
}
void main() {
auto a = iota(0, x + 1).array;
solve(a);
writefln(`%s total`, c);
}
void dout(Tuple)(Tuple idx) {
++c;
}
-
http://rextester.com/XGDL26042
What do you mean it breaks down? Your original code doesn't
print anything for s = 10_000 or s = 100_000, either.
Excuse me, this is my blemish! I forgot that the constant `x`
depends on `s`. Everything works correctly:
import std.stdio, std.algorithm, std.range;
void solve(Range)(Range r) {
cartesianProduct(r, r, r).filter!(i = i[0] * (y + 3 * z) +
i[1] * (y + 2 * z) + i[2] * (y + z) == s).each!dout;
}
const y = 65, z = 50, s = 10;
const x = s / (y + z);
void main() {
auto a = iota(0, x + 1);
solve(a);
}
auto dout(Tuple)(Tuple idx) {
writefln(`%s apples`, idx[0] + idx[1] + idx[2]);
writefln(`%s gingerbread`, idx[0] * 3 + idx[1] * 2 + idx[2]);
writefln(`%s pharynx tea`, idx[0] * 3 + idx[1] * 2 + idx[2]);
writefln(Sour: %s; semi-acid: %s; sweet: %s.\n, idx[0],
idx[1], idx[2]);
}
-
http://rextester.com/MMCI9993
Re: Replacing nested loops foreach using map/each/etc
On Monday, 25 May 2015 at 17:52:09 UTC, Dennis Ritchie wrote:
But why is the solution breaks down when `s = 1` ? :)
import std.stdio, std.algorithm, std.range;
int c;
const x = 12, y = 65, z = 50, s = 10;
Which is it, now? 4 or 5 zeros?
void solve(Range)(Range r) {
cartesianProduct(r, r, r).filter!(i = i[0] * (y + 3 * z) +
i[1] * (y + 2 * z) + i[2] * (y + z) == s).each!dout;
}
void main() {
auto a = iota(0, x + 1).array;
solve(a);
writefln(`%s total`, c);
}
void dout(Tuple)(Tuple idx) {
++c;
}
-
http://rextester.com/XGDL26042
What do you mean it breaks down? Your original code doesn't
print anything for s = 10_000 or s = 100_000, either.
Re: Replacing nested loops foreach using map/each/etc
On Monday, 25 May 2015 at 17:19:27 UTC, Meta wrote:
`each` doesn't support braces. There are 4 ways to write a
function/delegate literal in D (with a few minor variations):
Short form:
function(int i) = i;
(int i) = i
(i) = i
i = i
Long form:
function(int i) { return i; }
(int i) { return i; }
(i) { return i; }
{ return 0; }
http://dlang.org/expression.html#FunctionLiteral
function
Thanks.
But why is the solution breaks down when `s = 1` ? :)
import std.stdio, std.algorithm, std.range;
int c;
const x = 12, y = 65, z = 50, s = 10;
void solve(Range)(Range r) {
cartesianProduct(r, r, r).filter!(i = i[0] * (y + 3 * z) + i[1]
* (y + 2 * z) + i[2] * (y + z) == s).each!dout;
}
void main() {
auto a = iota(0, x + 1).array;
solve(a);
writefln(`%s total`, c);
}
void dout(Tuple)(Tuple idx) {
++c;
}
-
http://rextester.com/XGDL26042
Re: deserialization: creating a class instance without calling constructor
On Thursday, 21 May 2015 at 19:06:35 UTC, Jacob Carlborg wrote:
On 2015-05-21 11:06, Timothee Cour via Digitalmars-d-learn
wrote:
Can I create an instance of A without calling a constructor?
(see below)
Use case: for generic deserialiaztion, when the
deserialization library
encounters a class without default constructor for example (it
knows
what the fields should be set to, but doesn't know how to
construct the
object).
class A{
int x=2;
this(int x){
this.x=x;
}
}
This came up here:
https://github.com/msgpack/msgpack-d/issues/54#issuecomment-104136148
I provide some hacky solution for that in that thread but I
suspect it's
not safe and something is missing.
Here's how I do it in my serialization library Orange [1]
[1]
https://github.com/jacob-carlborg/orange/blob/master/orange/util/Reflection.d#L166
Thanks!
Re: Idiomatic way to call base method in generic code
On Mon, 25 May 2015 09:24:56 +, ZombineDev wrote:
alias can't refer to a nested member:
-
struct Point2 {
float x;
float y;
}
struct Line2 {
Point2 start;
Point2 end;
mixin Access;
// alias x1 = this.start.x; - this doesn't work :(
alias x1 = get!start.x;
alias y1 = get!start.y;
alias x2 = get!end.x;
alias y2 = get!end.y;
}
// I need to use a mixin to flatten the access :(
private mixin template Access()
{
ref auto get(string accessPattern)() inout {
return mixin(accessPattern);
}
}
-
i wonder if there is a reason for that limitation (except nobody
implemented that feature yet, of course).
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Description: PGP signature
Re: Idiomatic way to call base method in generic code
On Mon, 25 May 2015 09:24:56 +, ZombineDev wrote:
On Monday, 25 May 2015 at 07:57:49 UTC, ketmar wrote:
i don't know why you want that, but something like this may do:
auto callBaseMethod(string MTN, C, Args...) (inout C self, Args args) {
alias FSC = BaseClassesTuple!(C)[0];
return mixin(`self.`~FSC.stringof~`.`~MTN~(args));
}
writeln(d.callBaseMethod!toString);
Thanks!
note that this funny trick works even for `void` methods, due to magic of
`auto` return type.
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Re: Lazy variadic not working, any alternatives?
On Tuesday, 26 May 2015 at 05:22:26 UTC, Tofu Ninja wrote:
Actually the code seems to compile on 2.067.1 but definitely does
not work as expected.
Another example of Lazy variadic to show how it works...
void main(string[] args)
{
test(a(), b(), c());
}
bool a()
{
writeln(a);
return true;
}
bool b()
{
writeln(b);
return true;
}
bool c()
{
writeln(c);
return true;
}
void test(lazy bool[] c...)
{
for(int i = 0; i c.length; i++)
{
writeln(iteration: , i);
if(c[i]) writeln(success);
}
}
prints...
a
b
c
iteration: 0
a
b
c
success
a
b
c
iteration: 1
a
b
c
success
a
b
c
iteration: 2
a
b
c
success
a
b
c
Though because it still runs in order, maybe I can still make
this work...
Re: Lazy variadic not working, any alternatives?
On Tuesday, 26 May 2015 at 05:43:59 UTC, Tofu Ninja wrote: On Tuesday, 26 May 2015 at 05:22:26 UTC, Tofu Ninja wrote: Actually the code seems to compile on 2.067.1 but definitely does not work as expected. ... I guess it stems from the fact that its lazy (bool[]) Wish I could do (lazy bool)[]
Re: Lazy variadic not working, any alternatives?
On Tuesday, 26 May 2015 at 05:22:26 UTC, Tofu Ninja wrote:
So I was writing a simple parser and I wanted a functionality
that was basically try list of tokens in order and if any of
them fail, rewind input.
I tried using a lazy variadic function:
bool tok_and(lazy bool[] terms ...)
{
auto backup = getInputLocation();
for(int i = 0; i terms.length; i++)
{
if(terms[i] == false)
{
rewind(backup);
return false;
}
}
return true;
}
But this does not work because of BUG9110
https://issues.dlang.org/show_bug.cgi?id=9110
Any one have an idea how to achieve similar functionality
without a bunch of boilerplate at the call site? The lazy
version would have been nice because it would have allowed for:
if(tok_and(ident(), equal(), expression())) {...}
else if(tok_and(some(), other(), grammar())) {...}
else ...
Something like this appears to work:
import std.typetuple : allSatisfy;
enum implicityConvertibleToBool(T) = is(T : bool);
bool tok_and(Args...)(lazy Args terms)
if(allSatisfy!(implicitlyConvertibleToBool, Args))
{
auto backup = getInputLocation();
foreach(term; terms)
{
if(term == false)
{
rewind(backup);
return false;
}
}
return true;
}
Lazy variadic not working, any alternatives?
So I was writing a simple parser and I wanted a functionality
that was basically try list of tokens in order and if any of
them fail, rewind input.
I tried using a lazy variadic function:
bool tok_and(lazy bool[] terms ...)
{
auto backup = getInputLocation();
for(int i = 0; i terms.length; i++)
{
if(terms[i] == false)
{
rewind(backup);
return false;
}
}
return true;
}
But this does not work because of BUG9110
https://issues.dlang.org/show_bug.cgi?id=9110
Any one have an idea how to achieve similar functionality without
a bunch of boilerplate at the call site? The lazy version would
have been nice because it would have allowed for:
if(tok_and(ident(), equal(), expression())) {...}
else if(tok_and(some(), other(), grammar())) {...}
else ...
