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digitalmars.D.learn - String concat ~ with auto toString() feature?

reply AEon <AEon_member pathlink.com> writes:
I have been using ~ in many string functions, but was wondering if D counld not
automatrically "implicitly" convert any non-strings to strings in cases like
this:

   Warning(warn, "File '"~cfgPathFile~"', section '"~cfg_Sections[inSec]~
                 "', line #"~toString(i+1)~" requires"~
                 toString(cfg_Quote_Counts[inSec])~" \", not "~
                 toString(qcount)~"!");

with 

  void Warning(char[] from, char[] message)
  {
      printf("\n WARNING ( %.*s ) : \n   %.*s\n\n", from, message);
  }

I.e. qcount is a int, when surrounded by (string) ~, could it not be clear that
the user would want to have qcount converted to toString(qcount)?

Just wondering since in the above case AFAICT ~ is for string operations only,
so there should not be any ambiguity?

AEon
Mar 22 2005
next sibling parent reply Derek Parnell <derek psych.ward> writes:
On Tue, 22 Mar 2005 12:39:09 +0000 (UTC), AEon wrote:


 I have been using ~ in many string functions, but was wondering if D counld not
 automatrically "implicitly" convert any non-strings to strings in cases like
 this:
 
    Warning(warn, "File '"~cfgPathFile~"', section '"~cfg_Sections[inSec]~
                  "', line #"~toString(i+1)~" requires"~
                  toString(cfg_Quote_Counts[inSec])~" \", not "~
                  toString(qcount)~"!");
 
 with 
 
   void Warning(char[] from, char[] message)
   {
       printf("\n WARNING ( %.*s ) : \n   %.*s\n\n", from, message);
   }
 
 I.e. qcount is a int, when surrounded by (string) ~, could it not be clear that
 the user would want to have qcount converted to toString(qcount)?



I use this style ...

    Warning(warn, std.string.format(
        "File '%s', section '%s', line #%d requires %d, not %d!",
             cfgPathFile,
             cfg_Sections[inSec],
             i+1,
             cfg_Quote_Counts[inSec]),
             qcount
             ));

-- 
Derek Parnell
Melbourne, Australia
22/03/2005 11:54:48 PM
Mar 22 2005
parent AEon <AEon_member pathlink.com> writes:
In article <1rx44m7eaue9a$.11bm51tuirl2t$.dlg 40tude.net>, Derek Parnell says...

On Tue, 22 Mar 2005 12:39:09 +0000 (UTC), AEon wrote:


 I have been using ~ in many string functions, but was wondering if D counld not
 automatrically "implicitly" convert any non-strings to strings in cases like
 this:
 
    Warning(warn, "File '"~cfgPathFile~"', section '"~cfg_Sections[inSec]~
                  "', line #"~toString(i+1)~" requires"~
                  toString(cfg_Quote_Counts[inSec])~" \", not "~
                  toString(qcount)~"!");
 
 with 
 
   void Warning(char[] from, char[] message)
   {
       printf("\n WARNING ( %.*s ) : \n   %.*s\n\n", from, message);
   }
 
 I.e. qcount is a int, when surrounded by (string) ~, could it not be clear that
 the user would want to have qcount converted to toString(qcount)?



I use this style ...

    Warning(warn, std.string.format(
        "File '%s', section '%s', line #%d requires %d, not %d!",
             cfgPathFile,
             cfg_Sections[inSec],
             i+1,
             cfg_Quote_Counts[inSec]),
             qcount
             ));



Interesting example, I had been wondering how format() is actually used. Thanx.

AEon
Mar 22 2005
prev sibling next sibling parent reply "Regan Heath" <regan netwin.co.nz> writes:
On Tue, 22 Mar 2005 12:39:09 +0000 (UTC), AEon <AEon_member pathlink.com>  
wrote:

 I have been using ~ in many string functions, but was wondering if D  
 counld not
 automatrically "implicitly" convert any non-strings to strings in cases  
 like
 this:

    Warning(warn, "File '"~cfgPathFile~"', section '"~cfg_Sections[inSec]~
                  "', line #"~toString(i+1)~" requires"~
                  toString(cfg_Quote_Counts[inSec])~" \", not "~
                  toString(qcount)~"!");

 with

   void Warning(char[] from, char[] message)
   {
       printf("\n WARNING ( %.*s ) : \n   %.*s\n\n", from, message);
   }

 I.e. qcount is a int, when surrounded by (string) ~, could it not be  
 clear that
 the user would want to have qcount converted to toString(qcount)?

 Just wondering since in the above case AFAICT ~ is for string operations  
 only,
 so there should not be any ambiguity?



What you're essentially asking for is the ability to define opCat  
operators for the char[] built-in type.

To see what I mean here is some example code, pretend "String" is actually  
the built-in char[] type. The built in char type already has all the  
methods below (or their equivalent) except the opCat and opCatAssign  
operators for int and float, which is what you want to add.

import std.string;
import std.stdio;

class String
{
public:
	//built-in char[] already has methods similar/equivalent to these
	this()
	{
	}
	
	this(String s)
	{
		data = s.data.dup;
	}
	
	this(char[] s)
	{
		data = s.dup;
	}
	
	String opCat(char[] v)
	{
		String s = new String(this);
		s ~= v;
		return s;
	}
	
	String opCatAssign(char[] v)
	{
		int index = data.length;
		data.length = data.length + v.length;
		data[index..data.length] = v[];
		return this;
	}
	
	char[] toString()
	{
		return data;
	}
	
	//these methods are new
	String opCat(int v)
	{
		String s = new String(this);
		s ~= v;
		return s;
	}
	
	String opCatAssign(int v)
	{
		data ~= std.string.toString(v);
		return this;
	}

	
	String opCat(float v)
	{
		String s = new String(this);
		s ~= v;
		return s;
	}
	
	String opCatAssign(float v)
	{
		data ~= std.string.toString(v);
		return this;
	}

private:
	char[] data;
}

void main()
{
	String s = new String();	
	s = s ~ 5 ~ "regan" ~ 4.5; //calls opCat(int) opCat(char[]) and then  
opCat(float)
	writefln(s); //calls the toString method.
}

Regan
Mar 22 2005
parent AEon <AEon_member pathlink.com> writes:
Regan Heath says...

 Just wondering since in the above case AFAICT ~ is for string operations  
 only, so there should not be any ambiguity?



What you're essentially asking for is the ability to define opCat  
operators for the char[] built-in type.



Right.


To see what I mean here is some example code, pretend "String" is actually  
the built-in char[] type. The built in char type already has all the  
methods below (or their equivalent) except the opCat and opCatAssign  
operators for int and float, which is what you want to add.



Nice example.

So I am basically asking it would make sense to add the ~ operator for int/float
for char[]?

And if Walter would considder it, find it useful?

(I don't really need it, this is more of a possible feature suggestion).

AEon
Mar 22 2005
prev sibling parent Chris Sauls <ibisbasenji gmail.com> writes:
The ~ operator works with any array, or even with any struct or class 
with defines an opCat overload, so it might not be so easy.  Plus, would 
this mean DMD would auto-import std.string to get the toString() 
functions?  I could possibly understand it with classes though, since 
they should define their own .toString() method.

-- Chris Sauls

AEon wrote:

 Just wondering since in the above case AFAICT ~ is for string operations only,
 so there should not be any ambiguity?
 
 AEon
Mar 22 2005