modeling-app/docs/kcl/reduce.md

---
title: "reduce"
excerpt: "Take a starting value. Then, for each element of an array, calculate the next value,"
layout: manual
---

Take a starting value. Then, for each element of an array, calculate the next value,

using the previous value and the element.

```js
reduce(array: [u64], start: Sketch, reduce_fn: FunctionParam) -> Sketch
```


### Arguments

| Name | Type | Description | Required |
|----------|------|-------------|----------|
| `array` | `[u64]` |  | Yes |
| `start` | [`Sketch`](/docs/kcl/types/Sketch) | A sketch is a collection of paths. | Yes |
| `reduce_fn` | `FunctionParam` |  | Yes |

### Returns

[`Sketch`](/docs/kcl/types/Sketch) - A sketch is a collection of paths.


### Examples

```js
fn decagon = (radius) => {
  let step = 1 / 10 * tau()
  let sketch001 = startSketchAt([cos(0) * radius, sin(0) * radius])
  return reduce([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], sketch001, (i, sg) => {
  let x = cos(step * i) * radius
  let y = sin(step * i) * radius
  return lineTo([x, y], sg)
})
}
decagon(5.0)
  |> close(%)
```

![Rendered example of reduce 0](data:image/png;base64,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