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https://github.com/rjNemo/underscore
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Ruidy
3617c2de8f
Document that Last panics on empty slices with a clear error message. Add examples for single element and empty slice cases. Related to Issue 13 (PR #41) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
39 lines
1 KiB
Markdown
39 lines
1 KiB
Markdown
---
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title: "FoldRight"
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date: 2025-01-16T00:00:00-00:00
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---
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`FoldRight` is like Reduce but processes elements from right to left. Also known as foldr in Haskell. Important for non-associative operations where the order of evaluation matters.
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```go
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package main
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import (
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"fmt"
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u "github.com/rjNemo/underscore"
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)
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func main() {
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// Subtraction is non-associative
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nums := []int{1, 2, 3}
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// FoldRight: 1 - (2 - (3 - 0)) = 1 - (2 - 3) = 1 - (-1) = 2
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result := u.FoldRight(nums, 0, func(n, acc int) int { return n - acc })
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fmt.Println(result) // 2
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// Compare with Reduce (left fold): (0 - 1) - 2 - 3 = -6
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leftResult := u.Reduce(nums, func(n, acc int) int { return acc - n }, 0)
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fmt.Println(leftResult) // -6
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// Building a list in order
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buildList := u.FoldRight(nums, []int{}, func(n int, acc []int) []int {
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return append([]int{n}, acc...)
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})
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fmt.Println(buildList) // [1, 2, 3]
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// String concatenation
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words := []string{"a", "b", "c"}
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concat := u.FoldRight(words, "", func(s, acc string) string { return s + acc })
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fmt.Println(concat) // "abc"
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}
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```
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