going to a another function

what im trying to do is go to another function, that the user enters..

Code:

---

#include <stdio.h>
char choice[4];

int main() {
 printf ("enter a choice: ") ;
 scanf ("%s", choice);
 printf ("your choice is %s", choice);

 }

---

after " printf ("your choice is %s", choice);"
i want it to go to a function named after the variable choice...
for example if they enter math, i want it to go to the "math" function.
how would i do this , without a IF statement?

> how would i do this , without a IF statement?
With huge amounts of difficulty.
'C' isn't that kind of language.

Create a structure that contains a name and a function pointer, where all functions share the same prototype. Use an array of said structures, fixed at compile time. Use a loop + strcmp to check said array for selected name, and call the chosen function.

[edit]Of course, that usually would contain at least one if. I just noticed you didn't want any. Heh. That'll be more of the "huge amounts of difficulty". Or if not that, "exerciese in pointlessness".[/edit]

Now if you don't want them to all share the same prototype, that's where the "huge amounts of difficulty" come in...


Quzah.

My 2 cents.
Make a 2d array funcname storing the name(or the choices).Take a variable int a.
make a for loop.like for(i=0;strcmp(choice,funcname[i]);i++);
then you have value in int a corresponding to which function you want to call.Use a switch statement there.

:( what happened nobody responded.nobody pointed out an error.is everyone gawking at my stupidity ;)

You mean the strcmp() == 0?

you could also get around the strcmp. Since choice is only 4 char's long, you can use a switch statement.

Code:

---

switch( *((int *)choice) )  //this makes C think all 4 of those char's
 {                            //are individual bytes of an in

    case 'eno': //C will see this as an integer in the same fashion as well
            DoThisFunction();
            break;
 
  case 'wto':
            DoThisOtherFunction();
            break;
}

---

I have those words backwards because I'm assuming you're working with a little endian machine. If you're big endian, write them as you would in proper English. If you don't know what endian means, you should find out.

from what you say i gather it's the same with Intel/Motorola

Quote:

---

Originally Posted by dwks

You mean the strcmp() == 0?

---

yup.strcmp returns int 0,if both strings are same.is'nt it? and in c it is considered as false so loop will break

Quote:

---

Originally Posted by skorman00

you could also get around the strcmp

Code:

---

switch( *((int *)choice) )  //this makes C think all 4 of those char's
 {                            //are individual bytes of an in

    case 'eno': //C will see this as an integer in the same fashion as well
            DoThisFunction();
            break;
 
  case 'wto':
            DoThisOtherFunction();
            break;
}

---

---

Dont you think it will create some problem if the choices are of length 1 or 2?.May be i am wrong

Well if you're allowing switch/case, you can hide

> how would i do this , without a IF statement?

as

Code:

---

switch ( (cond) != 0 ) {
  case 1:  /* stuff for then*/
    break;
  case 0:  /* stuff for else*/
    break;
}

---

> switch( *((int *)choice)
Not only do you have endian problems, you have alignment problems.

Quote:

---

Originally Posted by Salem

> switch( *((int *)choice)
Not only do you have endian problems, you have alignment problems.

---

If you're talking about having choices that are < 4 characters, then yes you have to be a bit tricky. If not, would you mind elaborating?

From the gcc manual

Quote:

---

-Wcast-align
Warn whenever a pointer is cast such that the required alignment of the target is increased. For example, warn if a char * is cast to an int * on machines where integers can only be accessed at two- or four-byte boundaries.

---

On some machines, accessing mis-aligned data will get you a 'bus error' exception.