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Built-in types and functions are ones implicitly defined in every module.


See Types.



It calculates a size of a list or a map. It is generic and you can apply it to any list and map types.

Its time complexity is O(n) for lists and O(1) for maps.

\(list [a]) number
\(map {a: b}) number


It creates an error with its source information.

\(s any) error


It extracts source information from an error.

\(e error) any


It prints a debug message given as an argument.

Note that behavior of this function can change among system packages. You may not even see any messages with system packages whose systems do not have any consoles.

\(message string) none


It executes a function concurrently. Its return value is a future represented as a function that returns a result of the executed function.

\(\() a) \() a


It merges multiple lists into one by evaluating elements in the lists concurrently. Elements in each list are evaluated sequentially in order.

This function corresponds to the fan-in concurrency pattern in other languages where results of concurrent computation in multiple queues are merged into a queue.

\([[a]]) [a]