reduce() Function

## Function

reduce( function, initial, list, context )

Calls a rule or function for each item in a list, passing the result of each call to the next one, and returns the value of the last computation.

## Parameters

Keyword Type Description

`function`

Rule or Function Reference

Rule or expression function.

`initial`

Any Type

The accumulator's initial value.

`list`

Any Type

Array of elements that the function iterates through.

`context`

Any Type Array

Variable number of parameters passed directly into each function evaluation.

Any Type

## Usage considerations

### Referencing expressions and rules

Use `fn!functionName` to reference an expression function and `rule!ruleName` to reference a rule.

The initial accumulator value is given by initial.

### Using rules or functions with multiple arguments

To use rules or functions that take more than two arguments, use the merge() function. For example, given a rule `g(x, y, z)`, `reduce(rule!g, i, merge({a, b, c}, {d, e, f})) ` returns `g(g(g(i, a, d), b, e), c, f)`.

### Understanding results

Null lists return a null list without executing the function.

Returns a scalar value if the function called returns a scalar, and returns a list if the function called returns a list.

### Limitations and alternatives

Best used when the computation of each operation needs to use the result from the previous operation such as when the result of each operation is an array that should be appended to each other in order. The result from the previous operation is then passed to the subsequent operation as the parameter initial.

`a!forEach()` cannot be used within rules used in this function.

## Examples

You can experiment with this function in the test box below.

Test Input

Given a function `h(x, y)`, `reduce(fn!h,initial, {a, b, c}, v)` returns `h(h(h(initial, a, v), b, v), c, v)`.

`reduce(fn!sum, 0, {1, 2, 3})` returns `6`

Open in Github Built: Fri, Dec 03, 2021 (02:38:47 PM)