An untyped lambda calculus interpreter.

It has several useful features:

• Has support for the usual implicit parenthesization rules of lambda calculus

  • See the documentation for the parse function on here).

• Highlights the expression reduced last at each beta reduction step

  • (Can be disabled.)

• Allows bind lambda terms to symbols (definitions)

  • Lazy symbol substitution

  • Allows recursive definitions

• Has context-sensitive TAB completion, matching brace highlighter, and history support (thanks to rustyline).

• Allows escaping line breaks with &

  • The line will be saved to history as a single line.

• Has a non-interactive mode whose output is in a can be easily parsed by scripts

• Allows counting the number of reduction steps

...along with many other features; run with --help for more.

Screenshots

Installation

Install cargo if you don't have it, then run

$ cargo install lambda_calc

This will install the lambda_calc binary. Opitonally, you may use the --root option to install to a different directory; run man cargo-install for details.