generate

For generators.

Generate a list of values by successively invoking a closure.

Command Type

built-in

Signature

> generate {flags} (closure) (initial)

Parameters

closure: Generator function.
initial: Initial value.

Input/output types:

input	output
nothing	list<any>
list<any>	list<any>
table	list<any>
range	list<any>

Examples

Generate a sequence of numbers

> generate {|i| if $i <= 10 { {out: $i, next: ($i + 2)} }} 0
╭───┬────╮
│ 0 │  0 │
│ 1 │  2 │
│ 2 │  4 │
│ 3 │  6 │
│ 4 │  8 │
│ 5 │ 10 │
╰───┴────╯

Generate a continuous stream of Fibonacci numbers

> generate {|fib| {out: $fib.0, next: [$fib.1, ($fib.0 + $fib.1)]} } [0, 1]

Generate a continuous stream of Fibonacci numbers, using default parameters

> generate {|fib=[0, 1]| {out: $fib.0, next: [$fib.1, ($fib.0 + $fib.1)]} }

Generate a running sum of the inputs

> 1..5 | generate {|e, sum=0| let sum = $e + $sum; {out: $sum, next: $sum} }
╭───┬────╮
│ 0 │  1 │
│ 1 │  3 │
│ 2 │  6 │
│ 3 │ 10 │
│ 4 │ 15 │
╰───┴────╯

Notes

The generator closure accepts a single argument and returns a record containing two optional keys: ‘out’ and ‘next’. Each invocation, the ‘out’ value, if present, is added to the stream. If a ‘next’ key is present, it is used as the next argument to the closure, otherwise generation stops.

Additionally, if an input stream is provided, the generator closure accepts two arguments. On each invocation an element of the input stream is provided as the first argument. The second argument is the next value from the last invocation. In this case, generation also stops when the input stream stops.

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