Implementation of a parser, a compiler and an interpreter for a programming language called “SimplanPlus” which is based on ANTLR. The program takes as input a file (src/input.simplanplus) which is then analyzed.

The delivery contains 4 main points to follow for completion:

• lexical analysis that returns the list of lexical errors written in an output file (out/errors.txt);
• development of the program's Symbol Table (according to the ANTLR grammar used) and checking of:
  • undeclared identifiers/functions;
  • identifiers/functions declared multiple times in the same environment.
• development of a semantic analysis that:
  • verifies the correctness of the types, in particular if the number and types of the actual parameters of a function correspond to the formal ones;
  • checks the usage of uninitialized variables, assuming that functions never access global variables.
• implementation of the interpreter that interpretes the code outputted from the previous code generation phase.

SimpLanPlus is a simple imperative language based on ANTLR4, in which:

• programs are composed of:
  • a single expressions Exp;
  • a concatenation of declarations, statements and possible expressions { Dec+; Stm; Exp?* };
• declarations of variables/functions are of the form: type ID (without initialization);
• statements are sequences of commands (a program or the body of a function can be stm or dec stm);
• expressions are usual operations (>, ≥, <, ≤, ==) and logical operations (&&, ||, !);
• functions can be recursive (but not mutually);
• function bodies are of the type { Stm; Exp } and in this case the function, after evaluating Stm, returns the value of Exp;
• types also include the void type.