map!(char)(string) problem

[Jonathan M Davis via Digitalmars-d-learn]

On Sat, 03 May 2014 14:47:56 -0700
David Held via Digitalmars-d-learn <digitalmars-d-learn at puremagic.com>
wrote:

> import std.algorithm;
> 
> int toInt(char c) { return 1; }
> 
> void main()
> {
>      map!(a => toInt(a))("hello");
> }
> 
> Can someone please explain why I get this:
> 
> Bug.d(10): Error: function Bug.toInt (char c) is not callable using 
> argument types (dchar)
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> D:\D\dmd2\windows\bin\..\..\src\phobos\std\algorithm.d(425): Error: 
> template instance Bug.main.__lambda1!dchar error instantiating
> D:\D\dmd2\windows\bin\..\..\src\phobos\std\algorithm.d(411): 
> instantiated from here: MapResult!(__lambda1, string)
> Bug.d(10):        instantiated from here: map!string
> D:\D\dmd2\windows\bin\..\..\src\phobos\std\algorithm.d(411): Error: 
> template instance Bug.main.MapResult!(__lambda1, string) error
> instantiating Bug.d(10):        instantiated from here: map!string
> Bug.d(10): Error: template instance Bug.main.map!((a) => 
> toInt(a)).map!string error instantiating
> 
> I thought that string == immutable char[], but this implies that it
> is getting inferred as dchar[], I guess.

All strings are treated as ranges of dchar by Phobos.

http://stackoverflow.com/questions/12288465

If you really want to operate on strings as ranges of code units rather
than code points, then you need to use std.string.representation and
convert them to the equivalent integral types (e.g. immutable(ubyte)[]).


- Jonathan M Davis