OpenEuphoria

Re: string_exec()

• Posted by dcuny Mar 05, 2015
• 2036 views

As a follow up, I'm not sure I understand why you need to see Euphoria's variables. For example:

a = string_exec("a+b") 

The code that builds the string "a+b" obviously thinks there are variables called a and b, because it built a string expression containing those variables. But how does the code know about them?

Put a different way, if string_exec() were able to used named variables, would that be enough? For example:

sequence context = {{"a", 100}, {"b", 200}} 
string_exec(context, "myRoutine(a+b)+sin(a)") 

Would something like that satisfy your needs? That would be even simpler to write, and it could be written in pure Euphoria. I could cannibalize the parser I've written for Py to do this.

The question then becomes what's the best way to pass values of variables to string_exec. For something like a spreadsheet, the context would be pretty clunky. Passing the routine_id of a user-defined function that would resolve variables would be a more flexible approach, along the lines of:

sequence context = {{"a", 100}, {"b", 200}} 
 
-- returns {value, success_flag} 
function lookup_variable(sequence varName) 
   for i = 1 to length(context) 
      if equal(context[i][1], varName) then 
         -- return value and success flag 
         return {context[i][2], 1} 
      end if 
   end for 
   -- return bogus value and failure flag 
   return {0, 0} 
end function 
 
string_exec(routine_id("lookup_variable"), "myRoutine(a+b)+sin(a)") 

Or the function lookup_variable() could be supplied, and you'd just recode it to your needs.

Would that work?

- David