Module calc 

Calculator Expression Evaluator (Task 13)

Safe mathematical expression evaluator for agentic use cases:

• Sandboxed evaluation (no code injection)
• Column references for computed fields
• Built-in math functions (abs, sqrt, pow, etc.)

Grammar (Recursive Descent)

expr     → term (('+' | '-') term)*
term     → factor (('*' | '/' | '%') factor)*
factor   → unary
unary    → '-'? primary
primary  → NUMBER | COLUMN | '(' expr ')' | function
function → IDENT '(' (expr (',' expr)*)? ')'

Security Model

• No variable assignment (immutable)
• No loops (single-pass evaluation)
• No function definitions (allowlist only)
• Timeout: 1ms max for safety

Structs

Evaluator

Expression evaluator

Parser

Expression parser

Enums

BinaryOp

Binary operators

CalcError

Calculator error types

Expr

Expression AST node

UnaryOp

Unary operators

Functions

calculate

Parse and evaluate an expression in one step

parse_expr

Parse an expression without evaluating

Type Aliases

RowContext

Row context for evaluation