lambda_calculus

lambda_calculus is a simple implementation of the untyped lambda calculus in Rust.

The data and operators follow the Church encoding. The terms are implemented using De Bruijn indices, but can also be displayed using the classic lambda notation. Expressions containing the fixed-point combinator use its call-by-value variant and are adjusted so that they are compatible with as many β-reduction strategies as possible.

The library contains:

• Church numerals and arithmetic operations
• Church booleans
• Church pairs
• Church lists
• standard lambda terms and combinators
• a parser for lambda expressions with De Bruijn indices
• 7 β-reduction strategies with optional display of reduction steps

The implementation tries to find a compromise between the spirit of the lambda calculus and Rust's best practices; the lambda Terms implemented by the library are produced by functions (in order to allow arbitrary application), but they are not Copyable and the methods they provide allow memory-friendly disassembly and referencing their internals.

Documentation

Status

The library is already usable, but it is still a work in progress.

TODO

• additional tests
• β-reduction parallelization (at least to some extent)?
• further optimizations