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digitalmars.D - endsWith: wrong function call, no error

reply "Chris" <wendlec tcd.ie> writes:
The following code compiles:

import std.stdio;

void main() {

	auto text = "Hello world!";
	if (!std.algorithm.endsWith(text, "!" ".")) {
		writeln("No punctuation!");
	} else {
		writeln("Has punctuation");
	}
}

The bug is in line 6 a missing comma between "!" and ".":

!std.algorithm.endsWith(text, "!" ".")

If you insert the comma, it will behave as expected.

Is this ok or a bug?
Oct 21 2013
next sibling parent reply "monarch_dodra" <monarchdodra gmail.com> writes:
On Monday, 21 October 2013 at 15:12:36 UTC, Chris wrote:

 The following code compiles:

 import std.stdio;

 void main() {

 	auto text = "Hello world!";
 	if (!std.algorithm.endsWith(text, "!" ".")) {
 		writeln("No punctuation!");
 	} else {
 		writeln("Has punctuation");
 	}
 }

 The bug is in line 6 a missing comma between "!" and ".":

 !std.algorithm.endsWith(text, "!" ".")

 If you insert the comma, it will behave as expected.

 Is this ok or a bug?


It's a feature.
Oct 21 2013
parent reply "David Eagen" <davideagen mailinator.com> writes:
On Monday, 21 October 2013 at 15:18:18 UTC, monarch_dodra wrote:

 It's a feature.


I actually like that feature. It's me compose long strings in an 
easily viewable way without having to use concatenation and 
therefore additional allocation. Or, even to just comment on 
indvidual lines

string command =
      "/usr/bin/rm -rf / " // Don't worry, it'll be fine...
      ">/dev/null 2>/dev/null" // This way nobody will know about 
it.
Oct 21 2013
next sibling parent "Chris" <wendlec tcd.ie> writes:
On Monday, 21 October 2013 at 15:38:47 UTC, David Eagen wrote:

 On Monday, 21 October 2013 at 15:18:18 UTC, monarch_dodra wrote:

 It's a feature.


 I actually like that feature. It's me compose long strings in 
 an easily viewable way without having to use concatenation and 
 therefore additional allocation. Or, even to just comment on 
 indvidual lines

 string command =
      "/usr/bin/rm -rf / " // Don't worry, it'll be fine...
      ">/dev/null 2>/dev/null" // This way nobody will know 
 about it.


Well, in my program it was a bug that could comfortably hide for 
quite a while. It didn't really matter until now, because the 
program worked in spite of the bug. Only recent changes (today) 
brought it to light. If it does more harm than good, than it 
should be removed. It's too easy to forget a comma in an array or 
in a function like endsWith. What is more, this type of bug might 
only become apparent after a long long time. If you have

auto list = ["Joseph", "Mary", "Peter", "Ustinov", "Django" 
"Pope"];

and Django and Pope are the least likely go be selected, it can 
take a while until you realize that there's a bug. For my part, 
I've lived happily without this feature.
Oct 21 2013
prev sibling parent reply "David Nadlinger" <code klickverbot.at> writes:
On Monday, 21 October 2013 at 15:38:47 UTC, David Eagen wrote:

 I actually like that feature. It's me compose long strings in 
 an easily viewable way without having to use concatenation and 
 therefore additional allocation.


Concatenation of string literals doesn't need to allocate, as 
discussed here: 
http://d.puremagic.com/issues/show_bug.cgi?id=3827. It's trivial 
to handle the cases where you would've written "string1" 
"string2" instead of "string1" ~ "string2". Once overloaded 
operators come into play, it's a bit trickier, but if this case 
really occurred in your program, you could always add a pair of 
parens to fix it.

See also this post by Walter: 
http://forum.dlang.org/post/ibi742$gi2$1 digitalmars.com

David
Oct 21 2013
parent "David Eagen" <davideagen mailinator.com> writes:
On Monday, 21 October 2013 at 15:57:14 UTC, David Nadlinger wrote:

 Concatenation of string literals doesn't need to allocate, as 
 discussed here: 
 http://d.puremagic.com/issues/show_bug.cgi?id=3827. It's 
 trivial to handle the cases where you would've written 
 "string1" "string2" instead of "string1" ~ "string2". Once 
 overloaded operators come into play, it's a bit trickier, but 
 if this case really occurred in your program, you could always 
 add a pair of parens to fix it.

 See also this post by Walter: 
 http://forum.dlang.org/post/ibi742$gi2$1 digitalmars.com


Thanks for pointing that out. I've changed my stance then. It's 
causing difficult to find bugs and serves no useful purpose so it 
should go.

But since the thread you linked to is three years old it is 
apparently already decided and merely waiting implementation.
Oct 21 2013
prev sibling next sibling parent "Dicebot" <public dicebot.lv> writes:
On Monday, 21 October 2013 at 15:12:36 UTC, Chris wrote:

 The following code compiles:

 import std.stdio;

 void main() {

 	auto text = "Hello world!";
 	if (!std.algorithm.endsWith(text, "!" ".")) {
 		writeln("No punctuation!");
 	} else {
 		writeln("Has punctuation");
 	}
 }

 The bug is in line 6 a missing comma between "!" and ".":

 !std.algorithm.endsWith(text, "!" ".")

 If you insert the comma, it will behave as expected.

 Is this ok or a bug?


It C-compatible behavior, two string literal separated with only 
spaces are concatenated into one. So your code was essentially 
`endsWith(text, "!.")`
Oct 21 2013
prev sibling parent reply "bearophile" <bearophileHUGS lycos.com> writes:
Chris:


 Is this ok or a bug?


In my opinion it's a design bug inherited from C/C++ languages. 
Please vote for this issue:

http://d.puremagic.com/issues/show_bug.cgi?id=3827

Walter once agreed to remove this anti-feature.

Bye,
bearophile
Oct 21 2013
parent reply "Chris" <wendlec tcd.ie> writes:
On Monday, 21 October 2013 at 15:21:21 UTC, bearophile wrote:

 Chris:


 Is this ok or a bug?


 In my opinion it's a design bug inherited from C/C++ languages. 
 Please vote for this issue:

 http://d.puremagic.com/issues/show_bug.cgi?id=3827

 Walter once agreed to remove this anti-feature.

 Bye,
 bearophile


Hm. It took me a few minutes to find the bug in my program. I 
don't know yet what to think of it. If I wanted "!." I would 
possibly type this. Is there any real world scenario where this 
behavior could be useful?
Oct 21 2013
parent "Dicebot" <public dicebot.lv> writes:
On Monday, 21 October 2013 at 15:26:17 UTC, Chris wrote:

 Hm. It took me a few minutes to find the bug in my program. I 
 don't know yet what to think of it. If I wanted "!." I would 
 possibly type this. Is there any real world scenario where this 
 behavior could be useful?


It was necessary in C because it does not have built-in string 
concatenation. So only way to define pre-formatted string was 
something like this: `"Error in " __FILENAME__ ", run for your 
lives!"`

It does not seem that needed in D. I was using it out of habit 
but bearophile has convinced me it is a bad idea.
Oct 21 2013