Hi,

I would like to know if it is possible to convert a char[] to a struct that has a opCall(char[] str) function. For example:

import std.stdio;

char firstCharacterInString(pstring str)
{
    return str[0];
}


void main()
{
    writefln("first char = '%s'", firstCharacterInString("Hello World!")); // should print "first char = 'H'"
}

pstring = http://www.dprogramming.com/dstring.php

The above code will output something like this:

Error: cannot implicitly convert expression ("Hello World!") of type char[12u] to pstring

Is there any way to make D substitute "Hello World!" for pstring("Hello World!")? How do I get the above code to work without creating an instance of pstring like this:

pstring str = "Hello World!";

writefln("first char = '%s'", firstCharacterInString(str));

All help is appreciated!

Peace, Alan

Alan Smith wrote:
> I would like to know if it is possible to convert a char[] to a struct that has a opCall(char[] str) function. For example:
> 
> import std.stdio;
> 
> char firstCharacterInString(pstring str) { return str[0]; }
> 
> void main() { writefln("first char = '%s'", firstCharacterInString("Hello World!")); // should print "first char = 'H'" }
> 
> pstring = http://www.dprogramming.com/dstring.php
> 
> The above code will output something like this:
> 
> Error: cannot implicitly convert expression ("Hello World!") of type
> char[12u] to pstring
> 
> Is there any way to make D substitute "Hello World!" for pstring("Hello World!")? How do I get the above code to work without creating an instance of pstring like this:
> 
> pstring str = "Hello World!";
> 
> writefln("first char = '%s'", firstCharacterInString(str));

You can't do it with structs, as far as I can tell.

If pstring were a class, you could do this:

import std.stdio;

class pstring {
	char[] foo;
	this(char[] s) {
		foo = s;
	}
}

// note the ellipsis
char firstCharacterInString(pstring str...) {
    return str.foo[0];
}

void main() {
    writefln("first char = '%s'", firstCharacterInString("Hello World!"));
}

Perhaps if, in the future, structs get constructors, you could do something like this with structs.

Of course, you're free to make a wrapper class for your struct but that's somewhat self-defeating in my opinion. :-)

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