# [solved]Can C language have template?

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I'm using C to make a little game,with the project getting more huge,I found something I can't use C to implement. I need the function could take a parameter,which can be any type,including struct type.But I found I could't let the void* pointer take the struct type. Can any guys tell me how can I do to realize the feature such like template in C++? Thanks in advance. [Edited by - timaer on March 27, 2006 7:01:06 AM]

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You can make it an marco.

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In C your best bet is to use macros. If you want templates you will have to switch to C++. Is there any reason why you are using plain C?

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Hey bud,

All i can suggest is that you just go ahead and write out a function for each of the types. This is what C++ replaces the need to do, with templates.

Hope that helps,

Dave

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thanks Tjaalie and twanvl,could you give more detail about how to implement the function with macros?

and Hi,Dave,your idea is not bad ,if so,I have so many C function to be modified just becouse I need the feature which template can provide.I really hope I could rebuild my project and use C++ to do so,but I'm in a hurry to work the game out ,so I've to do it with C ;(

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EG:

#define TEMPLATE_COMPLEX_DECLARE( type ) \ typedef struct{ \    type real; \    type imaginary; \ }Complex##type;TEMPLATE_COMPLEX_DECLARE( float );TEMPLATE_COMPLEX_DECLARE( double );int main( int argc, char **argv ){    Complexdouble d;    d.real = 0.0f;    Complexfloat f;    f.imaginary = 1.0f;

[EDIT] arrgh, the source/code tags keep eating my "\" slashes...

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Quote:
 Original post by rip-offEG:*** Source Snippet Removed ***

That's horrid :P

Dave

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Quote:
Original post by Dave
Quote:
 Original post by rip-offEG:*** Source Snippet Removed ***

That's horrid :P

Dave

Thats templates in c :P

c++ templates arent too much better to look at, mind you, until you're used to them

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Quote:
 Original post by rip-offEG:*** Source Snippet Removed ***[EDIT] arrgh, the source/code tags keep eating my "\" slashes...

Hi,rip-off,you code looks nice,but still makes me a little confused(you know I'm bud;)

if I want to have a function like

int Animate_BOB(ANY_TYPE bob)

the ANY_TYPE could be monster or player struct type etc..

Could you give me the complete macro code for implementing this? ;)Thanks.

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Hmm, i suppose it would go like this:

#define DECLARE_ANIMATE_BOB( type ) \  int Animate_BOB##type( type bob );#define DEFINE_ANIMATE_BOB( type ) \  int Animate_BOB##type( type bob ) \  { \     do_stuff_with( bob ); \    return somevalue(); \ }// So in a header file(s), you ca just say:DECLARE_ANIMATE_BOB( Type1 );DECLARE_ANIMATE_BOB( Type2 );// And in the corresponding source file(s)DEFINE_ANIMATE_BOB( Type1 );DEFINE_ANIMATE_BOB( Type2 );

And you should be able to use the functions like so:

int result1 = Animate_BOBType1( bobType1 );
int result2 = Animate_BOBType2( bobType2 );

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Quote:
 Original post by rip-offHmm, i suppose it would go like this:*** Source Snippet Removed ***And you should be able to use the functions like so:int result1 = Animate_BOBType1( bobType1 );int result2 = Animate_BOBType2( bobType2 );

I suppose that's just what I need,anyway need some time to digest .Well,I'm a little sleepy,I'll study your code very hard tomorrow.Thank you so much , rip-off.And now I'd rather go to bed,Good night.

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Quote:
 Original post by rip-off#define DECLARE_ANIMATE_BOB( type ) \ int Animate_BOB##type( type bob );#define DEFINE_ANIMATE_BOB( type ) \ int Animate_BOB##type( type bob ) \ { \ do_stuff_with( bob ); \ return somevalue(); \ }// So in a header file(s), you ca just say:DECLARE_ANIMATE_BOB( Type1 );DECLARE_ANIMATE_BOB( Type2 );// And in the corresponding source file(s)DEFINE_ANIMATE_BOB( Type1 ); // you wouldn't put semicolons here would you?DEFINE_ANIMATE_BOB( Type2 );

would that expand to this:
int Animate_BOB##type( type bob ) \  { \     do_stuff_with( bob ); \    return somevalue(); \ };

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Quote:
 Original post by rip-off#define DECLARE_ANIMATE_BOB( type ) \ int Animate_BOB##type( type bob );#define DEFINE_ANIMATE_BOB( type ) \ int Animate_BOB##type( type bob ) \ { \ do_stuff_with( bob ); \ return somevalue(); \ }// So in a header file(s), you ca just say:DECLARE_ANIMATE_BOB( Type1 );DECLARE_ANIMATE_BOB( Type2 );// And in the corresponding source file(s)DEFINE_ANIMATE_BOB( Type1 ); // you wouldn't put semicolons here would you?DEFINE_ANIMATE_BOB( Type2 );

would that expand to this:
int Animate_BOB##type( type bob ) \  { \     do_stuff_with( bob ); \    return somevalue(); \ };

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I'm glad I never cared to use plain C. C++ for me is much better.

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Quote:
Quote:
 Original post by Alpha_ProgDesDEFINE_ANIMATE_BOB( Type1 ); // you wouldn't put semicolons here would you?DEFINE_ANIMATE_BOB( Type2 );

would that expand to this:
int Animate_BOB##type( type bob ) \  { \     do_stuff_with( bob ); \    return somevalue(); \ };

The extra semicolons are compilable apparently...

But yeah, I am just too used to putting them in.

It is better to omit them in the prototype, so this code won't compile:

DECLARE_ANIMATE_BOB( type ) // no semicolon

So a revised version:

#define DECLARE_ANIMATE_BOB( type ) \  int Animate_BOB##type( type bob )#define DEFINE_ANIMATE_BOB( type ) \  int Animate_BOB##type( type bob ) \  { \      do_stuff_with( bob ); \      return somevalue();  \  }DECLARE_ANIMATE_BOB( int );DEFINE_ANIMATE_BOB( int );

Unfourtunatly DEFINE_ANIMATE_BOB( int ) will still compile with out a semicolon, but I can't see a way around that right now...

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Quote:
Original post by rip-off
Quote:
Quote:
 Original post by Alpha_ProgDesDEFINE_ANIMATE_BOB( Type1 ); // you wouldn't put semicolons here would you?DEFINE_ANIMATE_BOB( Type2 );

would that expand to this:
int Animate_BOB##type( type bob ) \  { \     do_stuff_with( bob ); \    return somevalue(); \ };

The extra semicolons are compilable apparently...

But yeah, I am just too used to putting them in.

It is better to omit them in the prototype, so this code won't compile:

DECLARE_ANIMATE_BOB( type ) // no semicolon

So a revised version:

*** Source Snippet Removed ***

Unfourtunatly DEFINE_ANIMATE_BOB( int ) will still compile with out a semicolon, but I can't see a way around that right now...

I don't see a way for that to truly need a semi on the end.

The only way to require a semi is either like the above on a function declaration or something like this on a statement(s):
#define MY_MACRO(x) do {     do_stuff_with((x)); } while (false)

or:
#define MY_MACRO(x) if (true)     do_stuff_with((x)); else

But the second one is kinda risky.

But really, I see 0 ways for a function declaration to work o_O.

EDIT: Source is messing with my '\'.
EDIT2: Well, if you ABOSUTELY WANT a semi, you must add a '}', too:
#define DEFINE_ANIMATE_BOB(type)int Animate_BOB##type( type bob ) \  { \     do_stuff_with( bob ); \    return somevalue()//AndDEFINE_ANIMATE_BOB(int);}

[grin]

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Quote:
 Original post by rip-offEG:*** Source Snippet Removed ***[EDIT] arrgh, the source/code tags keep eating my "\" slashes...

I'm pretty sure C already has a complex number type.

#include <complex.h>int main() {  complex double number = 42.0+1.0i; }

Edit: Well, apparently imaginary constants aren't standard, but the complex type itself is.

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There is one way... but its so ugly I wouldn't do it.

Basically so the equivalent of:

void foo(){   // stuff}void foo(); // not actaully required, but allowed// IE#define DEFINE_ANIMATE_BOB( type ) \ int Animate_BOB##type( type bob ) \ { \     do_stuff_with( bob ); \     return somevalue();  \ }\ int Animate_BOB##type( type bob )

We insert a redundant declaration without a semicolon. It forces you to put in a semicolon, but its not pretty nor does it give any clue as to whats going on...

Quote:
Original post by smart_idiot
Quote:
 Original post by rip-offEG:*** Source Snippet Removed ***[EDIT] arrgh, the source/code tags keep eating my "\" slashes...

I'm pretty sure C already has a complex number type.

*** Source Snippet Removed ***

It was just an example of a POD that could be meaningfully templated. The OP already had some function / type in mind for templating...

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the complex type is in the standar of C.

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Why would you be bothered about it compiling without a semicolon? Okay, so it lets you be lazy, but as long as it will compile with the semicolon there then I don't see why it's a problem ...

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Quote:
 Original post by Bob JanovaWhy would you be bothered about it compiling without a semicolon?

Because the extra semicolon could break things like if/else statements if you don't take care of it.

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1) Complex floating point numbers were added in C99, most compilers support the older C89 standard.

2) It sounds like you're trying to shoe horn a C++ solution into C. Don't do that. Often, good C++ is bad C and good C is bad C++. I prefer C for what I do, but that's because I've decided C is the right tool for the job (everything I need, nothing I don't, and dealing with an established C code base). If I needed templates as a fundamental part of the design, then C would be one of the first languages I'd rule out as "the right tool".

3) I think lcc-win32 offers templates as an extension. Non-portable, but that may or may not be an issue.

4) The usual C solution is one function for each type (see OpenGL) or a union of structs with a type paramter:
typedef union {    struct { int type; } info;    struct { int type; double data; } type_double;    struct { int type; float  data; } type_float;    /* etc... */} MyTemplateType;enum {    MY_TEMPLATE_DOUBLE,    MY_TEMPLATE_FLOAT,    /* etc... */}int foo(MyTemplateType *t) {    switch(t->info.type) {        case MY_TEMPLATE_DOUBLE: {            /* Do stuff with t->type_double.data */            return 0;        }        case MY_TEMPLATE_FLOAT: {            /* Do stuff with t->type_float.data */            return 0;        }        default: { /* Error */ return -1; }    }}

If you find that too cumbersome, you just found one reason why C++ exists.

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HI,thanks so many guys to help me ,and provided so many idea to me.Thank you all