Question

I am working on certain script language. Values containing structure is

struct myvar
{
 char  name[NAMELEN];
 int   type;
 void* value;
}
type = 0  --> int* value
type = 1  --> char* value
type = 2  --> float* value

I faced some problem with arithmetic operations. It seems that I need to commit all sorts of type conversions over every single operation, that develops into writing a whole bunch of code for each of them, as in:

case 0:  // "="
 if(factor1.name)
 {
    if((factor1.type == 1) && (factor2.type==1))
    {
        free(factor1.value);
        int len = (strlen((STRING)factor2.value)+1)*sizeof(char);
        factor1.value = malloc(len);
        memcpy(factor1.value,factor2.value,len);
    }
    else if((factor1.type == 2) && (factor2.type==2))
    *(FLOAT*)factor1.value = *(FLOAT*)factor2.value;
    else if((factor1.type == 0) && (factor2.type==0))
    *(INTEGER*)factor1.value = *(INTEGER*)factor2.value;
    else if((factor1.type == 0) && (factor2.type==2))
    *(INTEGER*)factor1.value = *(FLOAT*)factor2.value;
    else if((factor1.type == 2) && (factor2.type==0))
    *(FLOAT*)factor1.value = *(INTEGER*)factor2.value;
    else
     GetNextWord("error");
 }
 break;

Is there some way to avoid this tiresome procedure? Otherwise I have no choice but to copy-paste this piece of code for each of “=”,”~”,”+”,”-“,”*”,”/”,”%”,”>”,”<“,”>=”,”<=”,”==”,”~=”,”AND”,”OR”

Answer 1

What about writing 3 toType functions:

char* toType0(myvar* from)
{
   if (from->type == 0) return (char*)(from->value);
   else if (from->type == 1) return itoa((int*)from->value);
   else...
}
int toType1(myvar* from)
{
   //convert to int...
}

Then in your conversion routines you can do:

 switch (factor1.type)
 {
    case 0:
     { char* other = toType0(&factor2);
     //assign or add or whatever....
     };
     break;
     case 1:
     { int other = toType1(&factor2);
     //assign or add or whatever....
     };
     break;
     ...
  }