function name as string

[CptDondo]

I think the answer to this is "no" but I figured I'd try....

I have a function name as a string:

funcName = "xyz";

and I have a function:

void xyz(blah) {}

Is there some way to call function xyz using the string contained in
funcName?

Something like (I know this is wrong)

(void)(*funcNam e)(blah)???

--Yan

[Karl Malbrain]

Re: function name as string

On Apr 19, 11:41 am, CptDondo <y...@NsOeSiPnA eMr.comwrote:

I think the answer to this is "no" but I figured I'd try....
>
I have a function name as a string:
>
funcName = "xyz";
>
and I have a function:
>
void xyz(blah) {}
>
Is there some way to call function xyz using the string contained in
funcName?
>
Something like (I know this is wrong)
>
(void)(*funcNam e)(blah)???
>
--Yan

Sure, just make a table that maps the string name to the function
pointer, look up the string name, and call the corresponding
function.

karl m

[=?utf-8?B?SGFyYWxkIHZhbiBExLNr?=]

Re: function name as string

CptDondo wrote:

I think the answer to this is "no" but I figured I'd try....
>
I have a function name as a string:
>
funcName = "xyz";
>
and I have a function:
>
void xyz(blah) {}
>
Is there some way to call function xyz using the string contained in
funcName?
>
Something like (I know this is wrong)
>
(void)(*funcNam e)(blah)???

When you run your program, you cannot rely on the names of functions
even being available at all, let alone having easy access to them,
sorry. You will need to save the names of all functions you wish to
call by name, and their addresses, manually.

struct function {
char *name;
void (*func)(void);
} functions[] = {
...
{ "xyz", &xyz },
...
};

You can then search in this list to see if the name exists, and if so,
call it.

name = "xyz";
for (i = 0; i != sizeof functions / sizeof *functions; i++) {
if (strcmp(functio ns[i], name) == 0) {
functions[i].func();
break;
}
}

(There are almost certainly better ways to search through the list,
and perhaps better ways to store the list, but the best way depends on
your needs.)

[CptDondo]

Re: function name as string

Harald van Dijk wrote:

CptDondo wrote:

>I think the answer to this is "no" but I figured I'd try....
>>
>I have a function name as a string:
>>
>funcName = "xyz";
>>
>and I have a function:
>>
>void xyz(blah) {}
>>
>Is there some way to call function xyz using the string contained in
>funcName?
>>
>Something like (I know this is wrong)
>>
>(void)(*funcNa me)(blah)???

>
When you run your program, you cannot rely on the names of functions
even being available at all, let alone having easy access to them,
sorry. You will need to save the names of all functions you wish to
call by name, and their addresses, manually.
>
struct function {
char *name;
void (*func)(void);
} functions[] = {
...
{ "xyz", &xyz },
...
};
>
You can then search in this list to see if the name exists, and if so,
call it.
>
name = "xyz";
for (i = 0; i != sizeof functions / sizeof *functions; i++) {
if (strcmp(functio ns[i], name) == 0) {
functions[i].func();
break;
}
}
>
(There are almost certainly better ways to search through the list,
and perhaps better ways to store the list, but the best way depends on
your needs.)
>

That's kind of what I figured.... I was trying to avoid the mother of
all switch statements... Or lookups, or whatever. Just trying to make
the next guy's job a bit easier.... :-)

Thanks,

--Yan

[Jack Klein]

Re: function name as string

On Thu, 19 Apr 2007 12:04:46 -0700, CptDondo <yan@NsOeSiPnAe Mr.com>
wrote in comp.lang.c:

Harald van D?k wrote:

CptDondo wrote:

I think the answer to this is "no" but I figured I'd try....
>
I have a function name as a string:
>
funcName = "xyz";
>
and I have a function:
>
void xyz(blah) {}
>
Is there some way to call function xyz using the string contained in
funcName?
>
Something like (I know this is wrong)
>
(void)(*funcNam e)(blah)???

When you run your program, you cannot rely on the names of functions
even being available at all, let alone having easy access to them,
sorry. You will need to save the names of all functions you wish to
call by name, and their addresses, manually.

struct function {
char *name;
void (*func)(void);
} functions[] = {
...
{ "xyz", &xyz },
...
};

You can then search in this list to see if the name exists, and if so,
call it.

name = "xyz";
for (i = 0; i != sizeof functions / sizeof *functions; i++) {
if (strcmp(functio ns[i], name) == 0) {
functions[i].func();
break;
}
}

(There are almost certainly better ways to search through the list,
and perhaps better ways to store the list, but the best way depends on
your needs.)

>
That's kind of what I figured.... I was trying to avoid the mother of
all switch statements... Or lookups, or whatever. Just trying to make
the next guy's job a bit easier.... :-)
>
Thanks,

DO NOT use a switch statement for this. Put the entries in the array
in sorted order and use bsearch().

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://c-faq.com/
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.l earn.c-c++

http://www.club.cc.cmu.edu/~ajo/docs/FAQ-acllc.html

[limkatkat]

Re: function name as string

Use a map?
like this?
map_get("abc");

On Apr 20, 2:41 am, CptDondo <y...@NsOeSiPnA eMr.comwrote:

I think the answer to this is "no" but I figured I'd try....
>
I have a function name as a string:
>
funcName = "xyz";
>
and I have a function:
>
void xyz(blah) {}
>
Is there some way to call function xyz using the string contained in
funcName?
>
Something like (I know this is wrong)
>
(void)(*funcNam e)(blah)???
>
--Yan

[websnarf@gmail.com]

Re: function name as string

On Apr 19, 11:41 am, CptDondo <y...@NsOeSiPnA eMr.comwrote:

I think the answer to this is "no" but I figured I'd try....
>
I have a function name as a string:
>
funcName = "xyz";
>
and I have a function:
>
void xyz(blah) {}
>
Is there some way to call function xyz using the string contained in
funcName?
>
Something like (I know this is wrong)
>
(void)(*funcNam e)(blah)???

You have to have a mapping from "xyz" to void (*xyz)(). The language
doesn't provide a natural way to do this, but there is a neat and
maintainable way of doing this. In one file, lets call it funcs.i,
write the following:

funcs.i:
----------
functionInvoke( xyz)
functionInvoke( anyotherfunctio nnameyoulike)
....

And from your C sources do the following:


program.c:
---------------

#define str_aux(x) #x
#define str(x) str_aux(x)
#define functionInvoke( x) str(x), &(x)
struct functionTable {
char * name;
void (* fn) ();
} fTable[] = {
#include "funcs.i"
};
#undef functionInvoke

So then you can add as many functions as you like to your table in the
funcs.i file. You can then search for the string name in fTable
amongst the names to determine which fn to call.

--
Paul Hsieh

http://www.pobox.com/~qed/

http://bstring.sf.net/