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https://github.com/rjNemo/underscore
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Ruidy
c8b01aacc2
- Add FoldRight: fold/reduce from right to left - Useful for non-associative operations - Comprehensive tests including comparison with Reduce - Benchmark included Example: FoldRight([1,2,3], 0, subtract) → 1-(2-(3-0)) = 2 Resolves Issue 20 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: Claude <noreply@anthropic.com>
80 lines
2.2 KiB
Go
80 lines
2.2 KiB
Go
package underscore_test
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import (
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"testing"
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"github.com/stretchr/testify/assert"
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u "github.com/rjNemo/underscore"
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)
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func TestFoldRight(t *testing.T) {
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nums := []int{1, 2, 3, 4}
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result := u.FoldRight(nums, 0, func(n, acc int) int { return n + acc })
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assert.Equal(t, 10, result)
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}
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func TestFoldRightEmpty(t *testing.T) {
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result := u.FoldRight([]int{}, 42, func(n, acc int) int { return n + acc })
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assert.Equal(t, 42, result)
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}
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func TestFoldRightSingleElement(t *testing.T) {
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result := u.FoldRight([]int{5}, 0, func(n, acc int) int { return n + acc })
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assert.Equal(t, 5, result)
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}
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func TestFoldRightSubtraction(t *testing.T) {
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// FoldRight: 1 - (2 - (3 - 0)) = 1 - (2 - 3) = 1 - (-1) = 2
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nums := []int{1, 2, 3}
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result := u.FoldRight(nums, 0, func(n, acc int) int { return n - acc })
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assert.Equal(t, 2, result)
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}
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func TestFoldRightDivision(t *testing.T) {
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// FoldRight with float: 2.0 / (4.0 / (8.0 / 1.0)) = 2.0 / (4.0 / 8.0) = 2.0 / 0.5 = 4.0
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nums := []float64{2.0, 4.0, 8.0}
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result := u.FoldRight(nums, 1.0, func(n, acc float64) float64 { return n / acc })
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assert.Equal(t, 4.0, result)
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}
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func TestFoldRightStrings(t *testing.T) {
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words := []string{"a", "b", "c"}
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result := u.FoldRight(words, "", func(s, acc string) string { return s + acc })
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assert.Equal(t, "abc", result)
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}
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func TestFoldRightVsReduce(t *testing.T) {
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nums := []int{1, 2, 3}
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// Reduce (left fold): (0 - 1) - 2 - 3 = -6
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reduceResult := u.Reduce(nums, func(n, acc int) int { return acc - n }, 0)
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assert.Equal(t, -6, reduceResult)
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// FoldRight: 1 - (2 - (3 - 0)) = 1 - (2 - 3) = 1 - (-1) = 2
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foldRightResult := u.FoldRight(nums, 0, func(n, acc int) int { return n - acc })
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assert.Equal(t, 2, foldRightResult)
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// They should be different for non-associative operations
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assert.NotEqual(t, reduceResult, foldRightResult)
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}
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func TestFoldRightBuildList(t *testing.T) {
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nums := []int{1, 2, 3}
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result := 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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assert.Equal(t, []int{1, 2, 3}, result)
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}
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func BenchmarkFoldRight(b *testing.B) {
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nums := make([]int, 1000)
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for i := range nums {
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nums[i] = i
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}
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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u.FoldRight(nums, 0, func(n, acc int) int { return n + acc })
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}
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}
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