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digitalmars.D - string composition

reply B.G. <B.G._member pathlink.com> writes:
Hi!

I was trying to port a C++ project to D.
I have many inplace string manipulations like this:

func("unexpected symbol: " + c);

where c may be any base type like char, int, etc.

In java those operations are part of the language
(this solution works perfectly with java language as such)
In C++ operator overloading is used and it's OK too.

Is there a nice way to do the above in D?
As far as I know, D operator overloading works only with objects and structs.
I'm not a fan of the own-string-class philosophy, so I'm actually talking about
char[].

This question is not about printf and friends.

I love the way it works in java, It's just perfect for SMALL things like the
example above.

What's your opinion?
Apr 28 2005
next sibling parent reply "Andrew Fedoniouk" <news terrainformatica.com> writes:
String concatenation is operator '~'

func("unexpected symbol: " ~ c);

but the best way is to use implicit format
func( format( "unexpected symbol: %d",i) );


"B.G." <B.G._member pathlink.com> wrote in message 
news:d4r3hk$16nq$1 digitaldaemon.com...

 Hi!

 I was trying to port a C++ project to D.
 I have many inplace string manipulations like this:

 func("unexpected symbol: " + c);

 where c may be any base type like char, int, etc.

 In java those operations are part of the language
 (this solution works perfectly with java language as such)
 In C++ operator overloading is used and it's OK too.

 Is there a nice way to do the above in D?
 As far as I know, D operator overloading works only with objects and 
 structs.
 I'm not a fan of the own-string-class philosophy, so I'm actually talking 
 about
 char[].

 This question is not about printf and friends.

 I love the way it works in java, It's just perfect for SMALL things like 
 the
 example above.

 What's your opinion?
Apr 28 2005
parent reply B.G. <B.G._member pathlink.com> writes:
In article <d4r6cu$1a7c$1 digitaldaemon.com>, Andrew Fedoniouk says...

String concatenation is operator '~'

func("unexpected symbol: " ~ c);


but ~ only works if both operands are arrays, the above doesn't even work
if c is a char. (at least with gdc compiler)


but the best way is to use implicit format
func( format( "unexpected symbol: %d",i) );

"B.G." <B.G._member pathlink.com> wrote in message 
news:d4r3hk$16nq$1 digitaldaemon.com...

 Hi!

 I was trying to port a C++ project to D.
 I have many inplace string manipulations like this:

 func("unexpected symbol: " + c);

 where c may be any base type like char, int, etc.

 In java those operations are part of the language
 (this solution works perfectly with java language as such)
 In C++ operator overloading is used and it's OK too.

 Is there a nice way to do the above in D?
 As far as I know, D operator overloading works only with objects and 
 structs.
 I'm not a fan of the own-string-class philosophy, so I'm actually talking 
 about
 char[].

 This question is not about printf and friends.

 I love the way it works in java, It's just perfect for SMALL things like 
 the
 example above.

 What's your opinion?
Apr 28 2005
parent "Unknown W. Brackets" <unknown simplemachines.org> writes:
Well, you could use format as above, or a temporary array:

char[] arr = "unexpected symbol: ";
arr ~= c;
func(arr);

Which isn't beautiful, yes.  If we had array literals, which I would 
love but we do not, that would most likely be the simplest way.

-[Unknown]



 In article <d4r6cu$1a7c$1 digitaldaemon.com>, Andrew Fedoniouk says...
 

String concatenation is operator '~'

func("unexpected symbol: " ~ c);


 
 
 but ~ only works if both operands are arrays, the above doesn't even work
 if c is a char. (at least with gdc compiler)
 
 

but the best way is to use implicit format
func( format( "unexpected symbol: %d",i) );
Apr 28 2005
prev sibling parent Derek Parnell <derek psych.ward> writes:
On Thu, 28 Apr 2005 16:38:12 +0000 (UTC), B.G. wrote:


 Hi!
 
 I was trying to port a C++ project to D.
 I have many inplace string manipulations like this:
 
 func("unexpected symbol: " + c);
 
 where c may be any base type like char, int, etc.
 
 In java those operations are part of the language
 (this solution works perfectly with java language as such)
 In C++ operator overloading is used and it's OK too.
 
 Is there a nice way to do the above in D?
 As far as I know, D operator overloading works only with objects and structs.
 I'm not a fan of the own-string-class philosophy, so I'm actually talking about
 char[].


Yes, it is unfortunate that string concatenation cannot be done as simply
as you would like. That is mainly because you can't provide operator
overrides to arrays. However, to get the effect you want is not a great
effort to do in D. Here some example code that I hope helps ..

<code>
private import std.stdio;
private import std.string;

// Template for arbitrary native data type string concatenation
template func(T)
{
    char[] func(char[] pData, T pExtra)
    {
        // convert input to string, concatenate and return result
        return std.string.format("%s%s", pData, pExtra);
    }
}

// Make a few aliases to improve readability.
alias func!(char)   funcmsg;
alias func!(int)    funcmsg;
alias func!(double) funcmsg;

void main()
{
    char lChar;
    int lInt;
    double lDouble;
    
    lChar = 'a';
    lInt = 3;
    lDouble = 2.41;
    
//    func("unexpected symbol: " ~ lChar);   // fails
//    func("unexpected symbol: " ~ lInt);    // fails
//    func("unexpected symbol: " ~ lDouble); //fails
    
    writefln( funcmsg("unexpected symbol: " , lChar) );
    writefln( funcmsg("unexpected symbol: " , lInt) );
    writefln( funcmsg("unexpected symbol: " , lDouble) );

}
</code>

-- 
Derek Parnell
Melbourne, Australia
29/04/2005 7:07:02 AM
Apr 28 2005