Ascend

Ascend is a friendly, general-purpose scripting language with optional C-style types. Write quick scripts without types, or add them where you want the checks: typed variables, functions, structs and collections are enforced, and many mistakes are reported before the program even runs. It comes with a package manager, a test runner, a REPL and a large standard library, and runs on Linux, macOS and Windows.

struct Animal {
    string name
    string sound() { return "..." }
    string to_string() { return f"{this.name} says {this.sound()}" }
}

struct Dog : Animal {
    string sound() { return "Woof" }
}

list<Animal> pets = [Dog("Rex"), Animal("Generic")]
for (Animal pet : pets) print(pet)

scores := {ada: 95, linus: 88, grace: 91}
best := max_by(keys(scores), name => scores[name])
printf("best: %s with %d\n", best, scores[best])

squares := [n * n for n in 1..=10 if n % 2 == 0]
response := http_get("https://api.github.com/repos/csubbdev/Ascend")
if (response.ok) print(json_parse(response.body).full_name)

Features

The language

• Optional C-style types: u8 age = 30, f64 area(f64 w, f64 h) { }, with i8–i64, u8–u64, f32, f64, bool, char, string, nullable types like string?, auto, and typed collections like list<i32> and map<string, f64>. Integer overflow is an error instead of a silent wrap.

• Structs with typed fields, methods, inheritance (struct Dog : Animal), operator overloading (operator+, operator==, operator<, ...) and special methods (to_string, iter, len); enums.

• Functions: default and named arguments, ...rest parameters, closures, lambdas (x => x * 2), multiple return values (return lo, hi).

• Expressive code: comprehensions ([x * x for x in xs if x > 0]), ranges (0..n), destructuring (a, b = b, a), ?? and ?., match, f-strings with format specs, raw and multi-line strings.

• C-style code works too: for (i32 i = 0; i < n; i++), i++, switch/case with fall-through, do/while, bodies without braces, casts, printf, and a main() that runs automatically.

• Errors: try/catch/finally/throw, clear messages that point at the problem, and tracebacks through function calls:

  script.asc:3:10: error: 'age' is declared as u8, so it can't hold 300 (u8 is 0 to 255)
   3 | u8 age = 300
     |          ^
  

The tools

• apkg, a package manager like pip: apkg install colors, then import colors. Packages come from the registry, GitHub, any git repository or a folder.
• ascend test runs your *_test.asc files.
• An interactive REPL, ascend --check to find errors without running, and syntax highlighting for VS Code.

The standard library (170+ builtin functions)

• Strings, lists, maps and sets, math, regular expressions, JSON and CSV
• Files, folders and paths; running programs and capturing their output
• HTTP requests, dates and times, base64, SHA-256, UUIDs

Quick start

cmake -S . -B build
cmake --build build
./build/ascend examples/shapes.asc     # run a program
./build/ascend                          # interactive REPL
./build/ascend test examples            # run the test files in a folder

See examples/ for more: functional.asc, methods.asc, scripting.asc, c_style.asc and others.

Install a package and use it:

./build/apkg install colors
./build/ascend -e 'import colors
print(colors.green("Hello!"))'

Documentation

• Language guide
• Standard library
• Packages and apkg
• Building, installing, testing and editor support
• Example programs

How it works

Stage	Source
Lexer: source text to tokens	src/lexer.cpp
Parser: tokens to a syntax tree	src/parser.cpp, src/include/ast.hpp
Checks before running (types of literals, break outside loops, ...)	src/semantic_analyzer.cpp, src/typecheck.cpp
Tree-walking interpreter	src/interpreter.cpp
Values, numeric types and checked arithmetic	src/value.cpp, src/numeric.cpp, src/types.cpp
Builtin functions, formatting and JSON	src/stdlib.cpp, src/stdlib_extra.cpp, src/format.cpp, src/json.cpp
Running other programs	src/process.cpp
Command line, REPL, ascend test	src/main.cpp, src/repl.cpp, src/runner.cpp, src/big_stack.cpp
Package manager (apkg) and finding packages for import	src/apkg_main.cpp, src/package_manager.cpp, src/packages.cpp

License

Apache License 2.0; see LICENSE.