goLogic errorMedium

Slice append mutation drops across function call

Time: 0:00

BugFind the bug and fix the code

What it should do

Append value to slice and return resulting slice. Example: pushItemToSlice([1, 2], 3) -> [1, 2, 3]

What happens instead

Appended item missing from slice after function call

package main

import "fmt"

func appendHelper(s []int, v int) {
	s = append(s, v)
}

func pushItemToSlice(items []int, val int) []int {
	appendHelper(items, val)
	return items
}

func main() {
	fmt.Println(pushItemToSlice([]int{1, 2}, 3))
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

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This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

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package main import "fmt" func appendHelper(s []int, v int) { s = append(s, v) } func pushItemToSlice(items []int, val int) []int { appendHelper(items, val) return items } func main() { fmt.Println(pushItemToSlice([]int{1, 2}, 3)) }

Slice append mutation drops across function call

What it should do

What happens instead

More logic errors to practise

Slice append mutation drops across function call

What it should do

What happens instead

More logic errors to practise