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digitalmars.D.bugs - [Issue 6547] New: Call to std.algorithm.remove causes compile error

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6547

           Summary: Call to std.algorithm.remove causes compile error
           Product: D
           Version: D2
          Platform: x86_64
        OS/Version: Mac OS X
            Status: NEW
          Severity: major
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: itsallaboutthedyo gmail.com


--- Comment #0 from Tim Keating <itsallaboutthedyo gmail.com> 2011-08-23
20:52:31 PDT ---
This minimal use case generates an error in std.algorithm:

    char[] s = "<html>Some fake HTML for your testing pleasure</html>".dup;
    auto start = s.find("<");
    auto len = s[start..$].find(">");
    s = s.remove(tuple(start, start+len+1));
    writeln(s);

The compile error I get from this is:

/usr/local/Cellar/dmd/2.054/src/phobos/std/algorithm.d(5826): Error: front(src)
is not an lvalue
/usr/local/Cellar/dmd/2.054/src/phobos/std/algorithm.d(5826): Error: front(tgt)
is not an lvalue

I pulled the most current version of Phobos from github and it has the same
problem, though there it occurs on line 5933.

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Aug 23 2011
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6547


Yuri Gorobets <yuri.gorobets gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yuri.gorobets gmail.com


--- Comment #1 from Yuri Gorobets <yuri.gorobets gmail.com> 2012-02-16 03:25:32
PST ---
(In reply to comment #0)

This behavior appears to be as designed. The compilation problem is caused by
special treatment of the "narrow strings" by std.array:

http://dlang.org/glossary.html#narrow%20strings

import std.array;
import std.algorithm;

void main()
{
    char[] s = "narrow".dup;

    s.remove(0); // Error: template std.algorithm.move(T) 
                 // does not match any function template declaration
                 // Error: template std.algorithm.move(T) cannot deduce 
                 // template function from argument types !()(dchar,dchar)

    // remove troubles are caused by the special treatment of narrow strings
    // front(s) doesn't return a char reference but dchar value instead:
    s.front = 'c';    // Error: s.front is not an lvalue
}

dchar version works fine:

void main()
{
    dchar[] u = "unicode"d.dup;
    u.remove(0);    // works fine
    u.front = 'c';
}

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Feb 16 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6547


Tim Keating <itsallaboutthedyo gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


--- Comment #2 from Tim Keating <itsallaboutthedyo gmail.com> 2012-03-13
15:39:44 PDT ---
I will say that I don't agree with this assessment -- the bug isn't really
about user error while operating on a narrow string, but about how the compiler
& library combo respond to that misuse. To wit, anytime a user gets a cryptic
error message buried deep inside a library in response to a simple mistake, you
have disempowered them from solving their own problem and derailed their
momentum in learning the language.

That said, under 2.058 the error message is now:

    test.d(11): Error: cannot implicitly convert expression (start) of type
char[] to ulong

Which makes it clear that find(string, string) is returning a slice. I think
this specific issue should be closed.

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Mar 13 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Tim Keating <itsallaboutthedyo gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |


--- Comment #3 from Tim Keating <itsallaboutthedyo gmail.com> 2012-03-16
12:26:44 PDT ---
The minimal use case described by Yuri above still occurs with 2.058.

If this isn't supposed to work for narrow strings, then perhaps a template
specialization for the unsupported types that raises a useful error message is
the right solution here?

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Mar 16 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
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SomeDude <lovelydear mailmetrash.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lovelydear mailmetrash.com
           Platform|x86_64                      |All
         OS/Version|Mac OS X                    |All
           Severity|major                       |normal


--- Comment #4 from SomeDude <lovelydear mailmetrash.com> 2012-04-22 03:24:38
PDT ---
Reduced to "normal"

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Apr 22 2012
prev sibling parent d-bugmail puremagic.com writes:
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Jonathan M Davis <jmdavisProg gmx.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
                 CC|                            |jmdavisProg gmx.com
         Resolution|                            |FIXED


--- Comment #5 from Jonathan M Davis <jmdavisProg gmx.com> 2012-06-08 02:05:32
PDT ---
As of 2.059, this is the error that you get:

 q.d(10): Error: cannot implicitly convert expression (start) of type char[] to
ulong
q.d(11): Error: template std.typecons.tuple does not match any function
template declaration
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/typecons.d(687): Error:
template std.typecons.tuple(T...) cannot deduce template function from argument
types !()(char[],_error_)

which is much better than the one originally reported.

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