splitter and matcher combined regex
Having to split and match seems slow(50%). Surely the regex splitter and matcher can be combined? Sometimes we just need to extract out and remove information simultaneously. I propose a new function called extractor that returns the matchAll and splitter's results but is optimized.
CT/RT annoyance
Consider
void foo(string A = "")(string B = "")
{
static if (A != "")
do(A);
else
do(B);
}
foo!("x");
foo("x");
This is necessary because D's templating and meta programming
system is frail.
While CTFE should take care of such things, it does not, consider
import(file) vs readText(file).
If do loads such a file then one must use tricks as above:
auto load(string n = "")(string n2 = "")
{
static if (n != "")
enum x = import(n);
else
auto x = readText(n2);
}
auto load2(string n)
{
enum x = import(n);
string y = import(n);
}
load2 fails to compile SIMPLY because n is a RT parameter.
Even if ctfe were to kick in, such as
load2("LiteralFileName.txt"), it is irrelevant because we can't
compile the code.
So tricks as in load are used, but it is very hacky and verbose
to do something very simple and natural.
This is precisely because readText cannot be used at compile time
since it dispatches to the OS's reading routines rather than
using import. This is not necessarily bad since we generally do
not want to import files in to the application at compile time,
but when we do it creates somewhat of a mess to unify code under
ctfe.
For example, if I create a function that loads a file and
processes it at RT then that code will not compile when used in
CTFE. If I modify it to import the text at CT then it does not
work at RT... even though the single point of breakage is the
import/readText line.
auto importOrReadText(string n)
{
if (__ctfe)
{
auto x = import(n);
} else
{
auto x = readText(n);
}
}
Fails for the same reasons above.
There is no way to get out of this conundrum(and therefor it is a
contradiction). It thin requires kicking the can down the street
and not read files at all but take text.
My suggestion is for someone to fix this. I'm not sure of the
solution.
maybe something like
auto importOrReadText(string n)
{
if (__ctfe)
{
auto x = import(ctfeFix(n));
} else
{
auto x = readText(n);
}
}
ctfeFix would be a special compiler semantic that takes a RT-like
variable and converts it to CT. It does this because it actually
can. It knows that n is ctfe'able and therefore n is actually a
string literal and will do some "magic" trick the compiler in to
seeing n for what it really is.
importOrReadText(rtFilename); // uses readText
importOrReadText("x.txt"); // uses import
Unfortunately __ctfe doesn't seem to actually work well... so I
suggest further
auto importOrReadText(string n)
{
static if (isKACT(n))
{
auto x = import(n);
// or auto x = import(ctfeFix(n));
} else
{
auto x = readText(n);
}
}
isKACT determines if n is actually known at compile time and
marks it n as essentially a CT constant as if it were passed as a
template parameter(internally it would probably just convert it
to a template parameter as if it were passed as such).
There may be other solutions.
Re: Range violation error when reading from a file
On Monday, 17 June 2019 at 00:22:23 UTC, Samir wrote:
On Sunday, 16 June 2019 at 23:55:41 UTC, lithium iodate wrote:
There is *very* likely to be a terminating new-line at the end
of the file (many editors add one without asking!). If that
the case, the last line seen by the loop will be empty and you
must not attempt to access any elements.
On Monday, 17 June 2019 at 00:02:37 UTC, aliak wrote:
The fail bit is only set after reading fails. So after you
read the last line, your eof will still return true, and hence
your range violation.
H...maybe you and lithium iodate were onto something.
Here is what the file looks like in vim:
> line 1
line 2
line 3
> line 4
line 5
~
~
~
The "5" in the last line is the last character I can put my
cursor on.
Also, if I run the program below with the same file, I don't
get any range violation errors:
import std.stdio;
import std.string;
void main() {
File file = File("test.txt");
string line;
while (!file.eof()) {
line = file.readln().strip;
//if (line[0] == '>') { // line 10
//writeln(line[1..$]);
//}
//else {
writeln(line);
//}
}
}
HOWEVER, the output is interesting. There IS a blank line
between the last line and the prompt:
$ dmd -run readfile.d
> line 1
line 2
line 3
> line 4
line 5
$
Any suggestions on how to rectify?
You could change the IF to
`if(line.length > 0 && line[0] == '>')`
or use strip itself;
`File("test.txt", "r").byLine.map!(line =>
line.strip(">")).writeln;`
For "> line 1" your code and this above will generate " line 1"
(note the leading space). To remove that change the string passed
to `strip` to include a space, e.g.;
`.strip("> ")).writeln;`
bye,
Norm
Re: Range violation error when reading from a file
On Sunday, 16 June 2019 at 23:55:41 UTC, lithium iodate wrote:
There is *very* likely to be a terminating new-line at the end
of the file (many editors add one without asking!). If that the
case, the last line seen by the loop will be empty and you must
not attempt to access any elements.
On Monday, 17 June 2019 at 00:02:37 UTC, aliak wrote:
The fail bit is only set after reading fails. So after you read
the last line, your eof will still return true, and hence your
range violation.
H...maybe you and lithium iodate were onto something.
Here is what the file looks like in vim:
> line 1
line 2
line 3
> line 4
line 5
~
~
~
The "5" in the last line is the last character I can put my
cursor on.
Also, if I run the program below with the same file, I don't get
any range violation errors:
import std.stdio;
import std.string;
void main() {
File file = File("test.txt");
string line;
while (!file.eof()) {
line = file.readln().strip;
//if (line[0] == '>') { // line 10
//writeln(line[1..$]);
//}
//else {
writeln(line);
//}
}
}
HOWEVER, the output is interesting. There IS a blank line
between the last line and the prompt:
$ dmd -run readfile.d
> line 1
line 2
line 3
> line 4
line 5
$
Any suggestions on how to rectify?
Re: Range violation error when reading from a file
On Sunday, 16 June 2019 at 23:44:49 UTC, Samir wrote: On Sunday, 16 June 2019 at 23:03:04 UTC, aliak wrote: stripping the last line could result in an empty line if it just has strippable characters? The last line of the file is just text but without a newline (\n) character or any other whitespace character at the end. I get the same error when I remove the strip function from the readln line. http://www.cplusplus.com/reference/ios/ios/eof/ The fail bit is only set after reading fails. So after you read the last line, your eof will still return true, and hence your range violation.
Re: Range violation error when reading from a file
On Sunday, 16 June 2019 at 23:44:49 UTC, Samir wrote: On Sunday, 16 June 2019 at 23:03:04 UTC, aliak wrote: stripping the last line could result in an empty line if it just has strippable characters? The last line of the file is just text but without a newline (\n) character or any other whitespace character at the end. I get the same error when I remove the strip function from the readln line. There is *very* likely to be a terminating new-line at the end of the file (many editors add one without asking!). If that the case, the last line seen by the loop will be empty and you must not attempt to access any elements.
Re: Range violation error when reading from a file
On Sunday, 16 June 2019 at 23:03:04 UTC, aliak wrote: stripping the last line could result in an empty line if it just has strippable characters? The last line of the file is just text but without a newline (\n) character or any other whitespace character at the end. I get the same error when I remove the strip function from the readln line.
Re: Range violation error when reading from a file
On Sunday, 16 June 2019 at 23:03:04 UTC, aliak wrote: stripping the last line could result in an empty line if it just has strippable characters? The last line is just the text of the last line. There is no newline character at the end. I also get the same error if I remove the strip function from the readln line.
Re: Range violation error when reading from a file
On Sunday, 16 June 2019 at 22:47:14 UTC, Samir wrote:
I am trying to read from a text file using the following code:
import std.stdio;
import std.string;
void main() {
File file = File("test.txt");
string line;
while (!file.eof()) {
line = strip(file.readln());
if (line[0] == '>') { // line 10
writeln(line[1..$]);
}
else {
writeln(line);
}
}
}
and I get the following error AFTER the last line is processed:
core.exception.RangeError@readfile.d(10): Range violation
??:? _d_arrayboundsp [0x448efa]
??:? _Dmain [0x4459f7]
Any idea what I am doing wrong? When processing the if
statement or writing the slice, am I inadvertently trying to
read a non-existent line in the file?
Thanks in advance
Samir
stripping the last line could result in an empty line if it just
has strippable characters?
Range violation error when reading from a file
I am trying to read from a text file using the following code:
import std.stdio;
import std.string;
void main() {
File file = File("test.txt");
string line;
while (!file.eof()) {
line = strip(file.readln());
if (line[0] == '>') { // line 10
writeln(line[1..$]);
}
else {
writeln(line);
}
}
}
and I get the following error AFTER the last line is processed:
core.exception.RangeError@readfile.d(10): Range violation
??:? _d_arrayboundsp [0x448efa]
??:? _Dmain [0x4459f7]
Any idea what I am doing wrong? When processing the if statement
or writing the slice, am I inadvertently trying to read a
non-existent line in the file?
Thanks in advance
Samir
Re: Suggest aesthetic way to Naming a module or a package with illegal lexical D lang keywords
On Sunday, June 16, 2019 5:53:30 AM MDT BoQsc via Digitalmars-d-learn wrote:
> On Sunday, 16 June 2019 at 11:38:27 UTC, rikki cattermole wrote:
> > The style guide has an opinion about this (you don't have to
> > follow it).
> >
> > https://dlang.org/dstyle.html#naming_keywords
>
> So if I follow dstyle guidelines on keywords, this would be a
>
> correct non-conflicting result:
> >module _auto._alias._abstract;
> >
> > void main(){
> >
> >}
>
> The underscore way, I kind of liking it, thanks for sourcing the
> idea.
Well, technically, per the style guide, the underscores would go at the end
of the names, not the front, but that's only if you're trying to follow the
style guide rather than be inspired by it.
- Jonathan M Davis
How does this template work?
How does the observerObject Template and function work? I'm struggling
because both use the same name and how is the template parameter R
deduced/where is it coming from? Looks like it's somehow implicitly
deduced.
class ObserverObject(R, E...){...}
template observerObject(E)
{
ObserverObject!(R, E) observerObject(R)(R range)
{
return new ObserverObject!(R, E)(range);
}
}
struct TestObserver {...}
auto observer = observerObject!int(TestObserver());
--
Robert M. Münch
http://www.saphirion.com
smarter | better | faster
Re: How does this template work?
On 17/06/2019 3:11 AM, Robert M. Münch wrote:
How does the observerObject Template and function work? I'm struggling
because both use the same name and how is the template parameter R
deduced/where is it coming from? Looks like it's somehow implicitly
deduced.
class ObserverObject(R, E...){...}
template observerObject(E)
{
ObserverObject!(R, E) observerObject(R)(R range)
{
return new ObserverObject!(R, E)(range);
}
}
struct TestObserver {...}
auto observer = observerObject!int(TestObserver());
observerObject is an eponymous template.
What this means (in essence) is the symbol inside the template block ==
template block.
Yes R is being inferred by the argument.
Re: Strange closure behaviour
On Sunday, 16 June 2019 at 01:36:38 UTC, Timon Gehr wrote: It's a bug. It's memory corruption. Different objects with overlapping lifetimes use the same memory location. Okay. Seen that way, it is clear to me why it's a bug. ... No, it's not the same. Python has no sensible notion of variable scope. >>> for i in range(3): pass ... >>> print(i) 2 Yuck. I got confused by this Python behavior: ls = [] for i in range(0, 5): ls.append(lambda x: x + i) for fun in ls: print(fun(0)) This prints: 4 4 4 4 4
Re: Suggest aesthetic way to Naming a module or a package with illegal lexical D lang keywords
On Sunday, 16 June 2019 at 11:38:27 UTC, rikki cattermole wrote:
The style guide has an opinion about this (you don't have to
follow it).
https://dlang.org/dstyle.html#naming_keywords
So if I follow dstyle guidelines on keywords, this would be a
correct non-conflicting result:
module _auto._alias._abstract;
void main(){
}
The underscore way, I kind of liking it, thanks for sourcing the
idea.
Re: Suggest aesthetic way to Naming a module or a package with illegal lexical D lang keywords
The style guide has an opinion about this (you don't have to follow it). https://dlang.org/dstyle.html#naming_keywords
Suggest aesthetic way to Naming a module or a package with illegal lexical D lang keywords
Do not ask why I want to do that, you can however suggest
alternative variations.
As you all might know,
2. The Identifiers preceding the rightmost are the Packages
that the module is in. The packages correspond to directory
names in the source file path. Package and module names cannot
be Keywords.
https://dlang.org/spec/module.html#module_declaration
The D Spec literally says that we cannot use these words in the
Module Names:
https://dlang.org/spec/lex.html#Keyword
Example, we can't Name Modules or Packages like that:
module auto.alias.abstract;
void main(){
}
I would like to know if there is any way to make it possible to
name Modules/Packages via preoccupied lexical words, or at least
receive some suggestions on some aesthetic naming for a
module/package that includes these lexical d words.
Examples:
module dauto.dalias.dabstract;
void main(){
}
module CustomAuto.CustomAlias.CustomAbstract;
void main(){
}
