Data structure for compiling postfix expression

Question

Hi I'm writing rpn calculator in C and I'd to compile rpn expression to byte-code. But I'm not sure what would be the data structure to represent them??? My stack data structure so far is

 struct stack_t{
        int type;
        union {  
              double val;
              char *str;
              /* probably some more */
             }u;
    };

Answer 1

It actually depends a lot on the feature set you are going to support. For example, if your calculator supports integers (e.g., integer division), you probably would need int in your union.

Answer 2

The advantage of RPN bytecode is that it doesn't need to be stored in a special structure. An array/vector/list will do. You need a stack to interpret it, but to store the program you should only convert each token to a bytecode instruction.

As for what types to put in your union, it really depends on the semantics of your calculator. Why do you want to be able to store strings? Do you plan on using strong typing?

Look into Forth, the canonical simple RPN language.