Pseudo-EXPR-Interpreter

Base

EXPR is a language which is used by students. The programs of this language consist of many rows of operations for assigning and printing values. It supports only unsigned integers that span from 0 to the max value of unsigned long int. The assignment operators are two.

• Assigning a number or an expression to a variable
• Declaring a function with only 1 parameter The read operators allows the user to input a value to a variable from the console, while the print operator prints an expression to the console.

Extension

The Pseudo EXPR Interpreter changes some of the syntax described above and also adds new functionality.

It adds a

• Support for recursive functions
• Support for arbitrary sized unsigned integers
• Support for conditions(if-else, ternary operator)
• Support for loops(while loop)
• Support for conditional operators(and, or)
• Support for equality and comparison operators

Syntax of the Pseudo EXPR language

Line → Instruction
Instruction → Var = Expr | Fun[Var] = Expr | if LogicalOr then Instruction else Instruction |
while LogicalOr do (Instruction)* done | print Expr | read Var

Fun → A | B | … | Z | AFun | BFun | … | ZFun
Var → a | b | … | z | aVar | bVar | … | zVar
Num → 0 | … | 9 | 1Num | … | 9Num

Expr       → If
If         → if LogicalOr then Expr else Expr | Ternary
Ternary    → LogicalOr ? Ternary : Ternary | LogicalOr
LogicalOr  → LogicalOr or LogicalAnd | LogicalAnd
LogicalAnd → LogicalAnd and Equaliry | Equality
Equality   → Equality == Comparison | Equality != Comparison | Comparison
Comparison → Comparsion (> | >= | <= | <) Arithmetic | Arithmetic  
Arithmetic → Arithmetic + Factor | Arithmetic - Factor | Factor
Factor     → Factor * Unary | Factor / Unary | Factor % Unary | Unary
Unary      → !Unary | Primitive
Primitive  → Var | Num | (Expr) | Fun[Expr]

You can check the docs branch for more information on the language!