CLI Calculator

A hand-built Python command-line calculator with its own lexer, parser, AST, and evaluator. It does not use eval().

Quick Start

python -m venv .venv
.venv\Scripts\activate
pip install -r requirements.txt
python -m calc "2 + 2 * 3"

Run interactive mode:

python -m calc

Run tests:

pytest

CLI Usage

python -m calc "2 + 2"
python -m calc --precision 50 "1 / 7"
python -m calc --angle deg "sin(90)"
python -m calc --format scientific "123456789"
python -m calc -f script.calc
"sqrt(81) + max(2, 7)" | python -m calc

Supported flags:

• -f, --file: evaluate expressions from a script file (one expression per line)
• --precision N: Decimal precision (1 to 200)
• --angle {rad,deg}: trigonometry angle mode
• --format {auto,fixed,scientific}: output formatting mode
• --version: print version
• --help: show CLI help

Full Feature List

1) Arithmetic and Operators

• Addition +, subtraction -, multiplication *, division /
• Integer division //, modulo %, exponentiation ^ and **
• Unary plus/minus (+x, -x, -(2+3))
• Parentheses with precedence handling (PEMDAS)
• Decimal-based numeric evaluation using decimal.Decimal

2) Number Literal Support

• Integer literals: 42
• Decimal literals: 3.1415
• Scientific notation: 2.5e-3
• Hex literals: 0xFF
• Binary literals: 0b1010
• Octal literals: 0o77

3) Variables, Constants, and Result Memory

• Variable assignment: x = 5
• Variable usage: x * 3
• Auto-updated answer variable: ans
• Built-in constants:
  • pi
  • e
  • tau
  • inf

4) User-Defined Functions

• Define functions: f(x) = x^2 + 1
• Call functions: f(10)
• Multi-parameter functions: g(a, b) = a + b
• Scoped argument binding per call
• Validation for duplicate parameters and incorrect argument counts

5) Built-In Functions

• Core helpers: abs, round, floor, ceil
• Power/root: pow, sqrt
• Aggregates: min, max
• Integer math: factorial, gcd
• Logarithms: log, log10, log2
• Trigonometry: sin, cos, tan

Notes:

• Log functions enforce valid domains (x > 0, base constraints).
• Trigonometric functions support radians and degrees.
• Precision-sensitive paths use Decimal-based computation.

6) REPL Commands

Start REPL with:

python -m calc

Commands:

• help: show command help and examples
• history: show command/result history
• clear history or history clear: clear history
• vars: list current variables (including ans)
• clear: clear user-defined variables and functions
• set precision N: update precision at runtime
• set angle deg|rad: change angle mode
• set format auto|fixed|scientific: change output mode
• quit or exit: leave REPL

Input handling:

• Empty lines are ignored
• Ctrl+C cancels current input without exiting
• Ctrl+D exits cleanly

7) Script and Pipe Modes

• Script mode: python -m calc -f script.calc
• Pipe mode: standard input is read line-by-line when stdin is not a TTY
• Script/piped lines that are empty or start with # are skipped
• Script errors are reported with line numbers and processing continues

8) Formatting and Precision Controls

• Output format modes:
  • auto
  • fixed
  • scientific
• Runtime and startup precision control
• Session precision applies to Decimal evaluation and display behavior

9) Config and History Persistence

• Config file: ~/.calcrc (JSON)
• Supported config keys:
  • precision
  • angle_mode
  • output_format
  • save_history
• History file: ~/.calc_history
• History can be loaded/saved across sessions (up to recent entries)

10) Error Handling

Custom error hierarchy with human-readable messages:

• CalcError
• LexerError
• ParseError
• EvaluationError
• DivisionByZeroError
• UndefinedVariableError

Behavior:

• Position-aware error messages
• Caret-style rendering for source errors
• Graceful REPL recovery after invalid input

Project Structure

• calc/lexer.py: tokenizes source input
• calc/parser.py: recursive-descent parser producing AST
• calc/ast_nodes.py: AST node model
• calc/evaluator.py: tree-walking evaluator
• calc/environment.py: variables/constants/functions state
• calc/formatter.py: output formatting strategies
• calc/engine.py: session orchestration
• calc/repl.py: interactive loop and commands
• calc/cli.py: command-line entrypoint and execution modes
• calc/config.py: config load/validate
• calc/history.py: session and persisted history
• tests/: unit and integration tests

Development

pip install -r requirements.txt
pytest
python -m calc