TheAlgorithms/Go · error

provided size is too small to use to slice string of len

Error message

provided size %d is too small to use to slice string %q of len %d

What it means

NewPolybius slices the character alphabet to 'size' characters; if size exceeds len(chars) the slice would go out of range, so the constructor rejects the (size, chars) combination naming both values.

Solutions

1. Supply an alphabet at least as long as size (e.g. 25 letters for a 5x5 square)
2. Lower size to fit the provided chars string
3. Include 'J' handling or extra symbols to extend a short alphabet

When it happens

Trigger: Thrown at cipher/polybius/polybius.go:31 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of TheAlgorithms/Go@5ba447ec5f (2026-09-02). Data as JSON: /api/errors/2450c180da097ef7. Report an issue: GitHub.

Appendix: source

Thrown at cipher/polybius/polybius.go:31

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// Polybius is struct having size, characters, and key
type Polybius struct {
	size       int
	characters string
	key        string
}

// NewPolybius returns a pointer to object of Polybius.
// If the size of "chars" is longer than "size",
// "chars" are truncated to "size".
func NewPolybius(key string, size int, chars string) (*Polybius, error) {
	if size < 0 {
		return nil, fmt.Errorf("provided size %d cannot be negative", size)
	}
	key = strings.ToUpper(key)
	if size > len(chars) {
		return nil, fmt.Errorf("provided size %d is too small to use to slice string %q of len %d", size, chars, len(chars))
	}
	for _, r := range chars {
		if (r < 'a' || r > 'z') && (r < 'A' || r > 'Z') {
			return nil, fmt.Errorf("provided string %q should only contain latin characters", chars)
		}
	}
	chars = strings.ToUpper(chars)[:size]
	for i, r := range chars {
		if strings.ContainsRune(chars[i+1:], r) {
			return nil, fmt.Errorf("%q contains same character %q", chars[i+1:], r)
		}
	}

	if len(key) != size*size {
		return nil, fmt.Errorf("len(key): %d must be as long as size squared: %d", len(key), size*size)
	}
	return &Polybius{size, chars, key}, nil
}

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