Nondescript

A simple, embeddable scripting language for C applications. Nondescript occupies a space similar to Lua: a small, single-file implementation that can be compiled into any C project with minimal fuss.

Features

• Single-file implementation — one .c and one .h, no dependencies beyond the C standard library
• C11 compatible (really C99 + _Alignof)
• AppleScript-style syntax — natural-language-inspired, case-insensitive
• Extensible grammar — register host commands with custom keyword patterns
• Chunk accessors — word 1 of myString, item 3 of myList, etc. You can register your own chunk types at runtime
• given blocks — pass a block of code to a function
• List comprehensions - set nonSpaces to every character of myString where it != ' '
• Pluggable allocators — pool and limit allocators included
• Slot-based C API - to (hopefully) make it hard to break GC
• A distinct 90s feel - for a bit of nostalgia

Building

Nondescript is designed to be compiled directly into your project:

#include "nondescript.h"

cc -o myapp myapp.c nondescript.c -lm

Quick Start

#include <stdio.h>
#include "nondescript.h"

int main(int argc, char **argv) {
    if (argc < 2) {
        fprintf(stderr, "usage: nds <script.nds>\n");
        return 1;
    }

    NDSConfig config = {0};
    NDSContext *ctx = NDSContext_new(&config);
    NDSStatus status = NDSContext_evaluateFile(ctx, argv[1]);
    if (status != NDSStatus_OK)
        fprintf(stderr, "%s\n", NDSContext_getError(ctx));
    NDSContext_free(ctx);
    return status == NDSStatus_OK ? 0 : 1;
}

-- Functions
function greet(name)
    println("hello, ", name, "!")
end function

greet("world")

-- Chunks and set expressions.
set firstItem to item 1 of ["foo", "bar", "baz"]
println("firstItem:", firstItem)

-- List comprehensions.
set nonSpaces to every character of "foo bar      baz" where it != ' '
println("nonSpaces:", nonSpaces)

-- Blocks.
function map(input)
    my result is []
    
    for each item i in input do
        append given(i) to result
    end for
    
    return result
end function

set plus2 to map([1, 2, 3]) given (i)
    return i + 2
end given

println("plus2:", plus2)

-- Block scope. Set will set the innermost binding of that variable.
-- Use "my" to claim an inner binding for yourself. All structures
-- introduce new scope.
function functionScope()
    my outer is "outer"
    if true then
        my outer
        set outer to "inner now!"
        println("inside if block:", outer)
    end if
    println("outside if block:", outer)
end function

functionScope()

-- Error handling is per-function.
function errorFunction()
    my NaN is 1 / 0
on error myError
    println("errored:", myError)
end function

errorFunction()

-- Errors bubble up
function innerError()
    raise nothing message "foo"
end function

function outerError()
    innerError()
on error myError
    println("got error with message", message of myError)
end function

outerError()

Examples

See the examples/ directory:

• calc — Defines functions in script, calls them from C via NDSContext_callFunction
• turtle — Registers natural-language host commands (move forward 100 steps, turn right 90 degrees), runs a script, and writes SVG output

Build an example:

cd examples
c11 -o turtle turtle.c ../nondescript.c
./turtle

License

LGPL

TODO

• The whole bifurcation of bytes/characters is weird...should probably just make separate types.
• Tons of little fixes and cleanups. NDSValue/NDSObject split is ugly...
• There's basically zero documentation.