quick start

Quick Start Guide

An LCL Module stores named expressions without evaluating them. A Frame supplies host values and evaluates definitions lazily, resolving references to other definitions as needed.

import asyncio

import lclang


async def main() -> None:
    module = lclang.define_module(
        "welcome",
        {
            "greeting": 'f"Hello, {name}!"',
            "result": "greeting + ' Welcome to lclang.'",
        },
    )
    async with lclang.define_frame(module, preset={"name": "Ada"}) as frame:
        assert await frame.get("result") == "Hello, Ada! Welcome to lclang."
        assert await frame.get("greeting") == "Hello, Ada!"


asyncio.run(main())

define_module parses all definitions up front. define_frame creates an independent cache. Asking for result evaluates greeting first; the second lookup returns its cached snapshot. Leaving the async with block closes the Frame and releases its owned tasks and resources.

For one expression in synchronous code:

import lclang

assert lclang.evaluate_sync("(value -> value * 2)(21)") == 42

Async code can parse once and evaluate with an explicit resolver:

import asyncio

import lclang


async def evaluate() -> None:
    expression = lclang.parse_expression("subtotal + tax")
    assert await lclang.evaluate(expression, {"subtotal": 40, "tax": 2}) == 42


asyncio.run(evaluate())