Interpreter written in Haskell for the While language described here. It builds the semantic function of the code and then applies it to the given state. In particular the interpreter performs a fixpoint calculation using the Knaster–Tarski theorem for calculating the semantics of the while construct. For further information see this.
To use the interpreter one may exploit the REPL function in the main or
stack ghci
and then the function i to interpret one program in one given state. For example:
i ("y:=1; while x != 1 do y:=y*x; x:=x-1","[x->7000]")
computes the factorial of 7000. The grammar of the language is:
The syntax is enriched with some syntactic sugar, always removed before interpreting the program:
| Sugar constructs |
|---|
| for |
| repeat |
| or |
| < |
| > |
| >= |
| != |
| ^ |
To build the executable you need happy installed, one parser generator for Haskell. To build the executable run:
./generateGrammar
stack build
To run the REPL mode use:
./i