TheAlgorithms/Go · warning

empty slice provided

Error message

empty slice provided

What it means

ErrEmptySlice is the sentinel error returned by math functions (e.g. Mode) that require at least one element; Mode returns (0, ErrEmptySlice) when len(numbers) == 0. As a declared package-level error, callers can compare with errors.Is / equality.

Source

Thrown at math/mode.go:19

// mode.go
// author(s): [CalvinNJK] (https://github.com/CalvinNJK)
// time complexity: O(n)
// space complexity: O(n)
// description: Finding Mode Value In an Array
// see mode.go

package math

import (
	"errors"

	"github.com/TheAlgorithms/Go/constraints"
)

// ErrEmptySlice is the error returned by functions in math package when
// an empty slice is provided to it as argument when the function expects
// a non-empty slice.
var ErrEmptySlice = errors.New("empty slice provided")

func Mode[T constraints.Number](numbers []T) (T, error) {

	countMap := make(map[T]int)

	n := len(numbers)

	if n == 0 {
		return 0, ErrEmptySlice
	}

	for _, number := range numbers {
		countMap[number]++
	}

	var mode T
	count := 0

View on GitHub (pinned to 5ba447ec5f)

Solutions

1. Check len(numbers) > 0 before calling Mode and handle the empty case explicitly.
2. Use errors.Is(err, math.ErrEmptySlice) to detect it and return a domain-appropriate default.
3. Fix upstream data loading so the slice is actually populated.

Example fix

// before
mode, err := math.Mode(values) // err = ErrEmptySlice

// after
if len(values) == 0 {
    return 0, nil // or a domain default
}
mode, err := math.Mode(values)

if len(values) == 0 {
    return 0, nil // define a default for the empty case
}
mode, err := math.Mode(values)

func nonEmpty[T any](xs []T) bool {
    return len(xs) > 0
}

mode, err := math.Mode(values)
if errors.Is(err, math.ErrEmptySlice) {
    return 0, nil // or propagate a domain-specific empty result
}
if err != nil {
    return 0, err
}

When it happens

Trigger: Calling math.Mode with an empty slice: Mode([]int{}) or Mode(someSlice) where the slice was never populated or was filtered down to zero elements.

Common situations: Reading an empty CSV/file into a slice; filtering that removes all items; a config list left empty; early-return paths where the caller forgot to check length before computing statistics.

Related errors

• integer overflow
• negative Exponent provided
• no Modular Inverse exists
• factorization failed
• ErrEmptyDequeue

AI-assisted analysis of TheAlgorithms/Go@5ba447ec5f (2026-09-02). Data as JSON: /api/errors/96a22837307684fa. Report an issue: GitHub.