Marslang language and API reference#

This reference describes the Rust interpreter as of rs-0.9.0, including dynamic numeric type tracking and the expanded std.math package. The source extension is .mars; earlier releases used .mrs. Use the matching source checkout for the filenames documented here. These API documents and release notes are eligible for Git tracking. Discussion notes elsewhere under docs/ remain local.

Reference#

Language syntax: variables, functions, families, and control flow.
Strings and slicing: Unicode characters, reversal, and strict bounds.
Collections: arrays, sets, pairs, maps, and copying.
Built-ins and errors: input/output, conversions, and runtime errors.
std.math: 51 math functions and six constants, written in Marslang on native float primitives.
std.containers: stack, queue, deque, and priority queue.
std.strings: splitting, searching, trimming, case, and padding.
std.types: a value's kind, family checks.
std.time: clocks and sleeping.
std.Decorator: @Decorator.private and @Decorator.subclass methods.

Install#

Released builds need no Rust toolchain and install into your home directory:

powershell

irm https://marslang.kevin-z.com/install.ps1 | iex

curl -fsSL https://marslang.kevin-z.com/install.sh | sh

Both accept --use std,ext (-Use in PowerShell) for the package sets to install; std is built into the interpreter, and ext is not published yet. marslang pkgs prints where packages you install are imported from.

Run#

From an installed interpreter, or with Rust from the repository root:

marslang docs/api/examples/strings.mars
cargo run -- docs/api/examples/strings.mars

The runnable example prints:

text

CDE
EDCBA
ABCDE
3
é👨‍👩‍👧‍👦
0

Use cargo test to run the execution tests, which run programs in the interpreter and check their output. The example above is also an execution test.

Current limits#

Programs run in a Rust tree-walking interpreter. The language is not self-hosted yet. Additional standard-library packages, the remaining decorators (static, class, overload), match, and async remain unimplemented. General named arguments are deferred; only slicing accepts reverse=. Proposed packages are not APIs.

The lex command uses a separate lexer from the parser. The REPL reruns its accumulated source rather than retaining a persistent runtime; it shows only new output.