C++ interpreter conceptual problem
- by Jan Wilkins
I've built an interpreter in C++ for a language created by me.
One main problem in the design was that I had two different types in the language: number and string. So I have to pass around a struct like:
class myInterpreterValue
{
myInterpreterType type;
int intValue;
string strValue;
}
Objects of this class are passed around million times a second during e.g.: a countdown loop in my language.
Profiling pointed out: 85% of the performance is eaten by the allocation function of the string template.
This is pretty clear to me: My interpreter has bad design and doesn't use pointers enough. Yet, I don't have an option: I can't use pointers in most cases as I just have to make copies.
How to do something against this? Is a class like this a better idea?
vector<string> strTable;
vector<int> intTable;
class myInterpreterValue
{
myInterpreterType type;
int locationInTable;
}
So the class only knows what type it represents and the position in the table
This however again has disadvantages:
I'd have to add temporary values to the string/int vector table and then remove them again, this would eat a lot of performance again.
Help, how do interpreters of languages like Python or Ruby do that? They somehow need a struct that represents a value in the language like something that can either be int or string.
