Hello, World!

Create a file named hello.co:

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log['hello, world']

Two things already differ from the languages you know: calls use square brackets (log[...], never log(...)) and strings use single quotes. These are the two most common reflexes to retrain, and the compiler will remind you if you slip.

Run it compiled — Crow transpiles to Rust, builds a native binary, and executes it:

crow run hello.co

hello, world

Or run it interpreted for instant startup while you're iterating:

crow run -i hello.co

The two modes are guaranteed to agree — the project's test suite diffs their outputs on a growing corpus of programs, including every code block in this book. Interpret while you explore; compile when you ship. That's the whole workflow.

One more taste of what's ahead — interpolation uses paired backticks, and a for loop is an expression that runs in parallel:

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name = 'crow'
log['hello, `name`']

squares = for x in [1, 2, 3, 4]
    x * x
log[squares]

hello, crow
[1, 4, 9, 16]