tricu (pronounced "tree-shoe") is a purely functional interpreted language implemented in Haskell. It is fundamentally based on the application of Tree Calculus terms, but minimal syntax sugar is included to provide a useful programming tool.

tricu is under active development and you should expect breaking changes with every commit.

tricu is the word for "tree" in Lojban: (x1) is a tree of species/cultivar (x2).

Features

Tree Calculus operator: t
Immutable definitions: x = t t
Lambda abstraction: id = (a : a)
List, Number, and String literals: [(2) ("Hello")]
Function application: not (not false)
Higher order/first-class functions: map (a : append a "!") [("Hello")]
Intensionality blurs the distinction between functions and data (see REPL examples)
Simple module system for code organization

REPL examples

tricu < -- Anything after `--` on a single line is a comment
tricu < id = (a : a) -- Lambda abstraction is eliminated to tree calculus terms
tricu < head (map (i : append i " world!") [("Hello, ")])
tricu > "Hello,  world!"
tricu < id (head (map (i : append i " world!") [("Hello, ")]))
tricu > "Hello,  world!"

tricu < -- Intensionality! We can inspect the structure of a function or data.
tricu < triage = (a b c : t (t a b) c)
tricu < test = triage "Leaf" (z : "Stem") (a b : "Fork")
tricu < test (t t)
tricu > "Stem"
tricu < -- We can even convert a term back to source code (/demos/toSource.tri)
tricu < toSource not?
tricu > "(t (t (t t) (t t t)) (t t (t t t)))"
tricu < -- or calculate its size (/demos/size.tri)
tricu < size not?
tricu > 12

tricu < -- REPL Commands:
tricu < !definitions  -- Lists all available definitions
tricu < !output       -- Change output format (Tree, FSL, AST, etc.)
tricu < !import       -- Import definitions from a file
tricu < !exit         -- Exit the REPL
tricu < !clear        -- ANSI screen clear
tricu < !save         -- Save all REPL definitions to a file that you can !import
tricu < !reset        -- Clear all REPL definitions
tricu < !version      -- Print tricu version

Installation and Use

You can easily build and run this project using Nix.

Quick Start (REPL):
- nix run git+https://git.eversole.co/James/tricu
Build executable in ./result/bin:
- nix build git+https://git.eversole.co/James/tricu

./result/bin/tricu --help

tricu Evaluator and REPL

tricu [COMMAND] ... [OPTIONS]
  tricu: Exploring Tree Calculus

Common flags:
  -? --help       Display help message
  -V --version    Print version information

tricu [repl] [OPTIONS]
  Start interactive REPL

tricu eval [OPTIONS]
  Evaluate tricu and return the result of the final expression.

  -f --file=FILE  Input file path(s) for evaluation.
                    Defaults to stdin.
  -t --form=FORM  Optional output form: (tree|fsl|ast|ternary|ascii|decode).
                    Defaults to tricu-compatible `t` tree form.

tricu decode [OPTIONS]
  Decode a Tree Calculus value into a string representation.

  -f --file=FILE  Optional input file path to attempt decoding.
                    Defaults to stdin.

Collaborating

I am happy to accept issue reports, pull requests, or questions about tricu via email.

If you want to collaborate but don't want to email back-and-forth, please reach out via email once to let me know and I will provision a git.eversole.co account for you.

Acknowledgements

Tree Calculus was discovered by Barry Jay.

treecalcul.us is an excellent website with an intuitive Tree Calculus code playground created by Johannes Bader that introduced me to Tree Calculus.