Calculator

An implementation of a programming-language calculator.

Features

• Arithmetic: +,-,*,/
• Parentheses
• Variables
• Assignment operators: =,+=,-=,*=,/=
• Unary increment/decrement
• In-expression assignments

Algorithm: Precedence Climbing

• Resources
  • Operator-precedence parser
  • Parsing approaches
  • More about precedence climbing
• Main advantages: efficient, relatively simple.
• Main disadvantage: ambiguous unary-binary operators with non-equal precedence is not easily supported.

Grammar

1. NUM:=[0-9]*
2. VAR:=[a-z;A-Z]+[a-z;A-Z;0-9]*
3. TERMINAL:={NUM|VAR}
4. ASSIGN:={VAR}[=,+=,-=,*=,/=]{EXPR}
5. EXPR:= ({EXPR}) || ASSIGN || SUM || MUL || DIV || SUB || {VAR}++ || ++{VAR} || {VAR}-- || --{VAR}