Named Arguments

Trailing parameters can declare defaults, which makes them optional and nameable at the call site:

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fn greet[name, greeting = 'hello']
    return '`greeting`, `name`'

log[greet['crow']]
log[greet['crow', 'hey']]
log[greet['crow', greeting = 'welcome']]

hello, crow
hey, crow
welcome, crow

The rules are exactly three:

1. Named parameters come after all positional ones
2. A named parameter must have a default — that's what makes it optional
3. Callers may use position or name for those slots — both are fine

You'll use this constantly with builtins: fmt[x, decimals = 2], sort[df, 'age', desc = true], sum[m, axis = 0]. It's the same mechanism everywhere — there is no separate "keyword argument" system for builtins versus your functions.