TheAlgorithms/C-Sharp · error · ArgumentException

Array is empty.

Error message

Array is empty.

What it means

Tanh.Compute rejects zero-length arrays: the hyperbolic tangent of an empty vector is undefined in this library, so it throws ArgumentException ('Array is empty.') after the null check when input.Length == 0.

Solutions

1. Guard with input.Length > 0 before calling and return an empty array early
2. Fix the batch/chunk producer so empty batches are skipped
3. Catch ArgumentException and treat it as the empty-input case

Example fix

// before
var result = Tanh.Compute(batch);
// after
var result = batch.Length > 0 ? Tanh.Compute(batch) : Array.Empty<double>();

if (input is null || input.Length == 0) return Array.Empty<double>();

static bool IsNonEmpty(double[]? a) => a is { Length: > 0 };

try { return Tanh.Compute(input); }
catch (ArgumentException ex) when (ex.Message == "Array is empty.") { return Array.Empty<double>(); }

When it happens

Trigger: Calling Tanh.Compute(Array.Empty<double>()) or on an array produced by an empty slice, empty deserialization, or a filter that matched nothing.

Common situations: Empty mini-batches in ML inference loops; empty JSON arrays from an API; chunking logic that produced a final zero-size chunk.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• Array is empty.
• Error value is not on interval (0.0; 1.0).
• Input must be a non-negative integer.
• input
• Invalid parameter settings for Ascon Hash

AI-assisted analysis of TheAlgorithms/C-Sharp@96e2905cab (2026-09-13). Data as JSON: /api/errors/82e0b1cde7b3ea87. Report an issue: GitHub.

Appendix: source

Thrown at Algorithms/Numeric/Tanh.cs:38

        // For a single double, we can directly use the optimized Math.Tanh method.
        return Math.Tanh(input);
    }

    /// <summary>
    ///     Compute the Hyperbolic Tangent (Tanh) function element-wise for a vector.
    /// </summary>
    /// <param name="input">The input vector of real numbers.</param>
    /// <returns>The output vector of real numbers, where each element is in the range [-1, 1].</returns>
    public static double[] Compute(double[] input)
    {
        if (input is null)
        {
            throw new ArgumentNullException(nameof(input));
        }

        if (input.Length == 0)
        {
            throw new ArgumentException("Array is empty.");
        }

        var outputVector = new double[input.Length];

        for (var index = 0; index < input.Length; index++)
        {
            // Apply Tanh to each element using the optimized Math.Tanh method.
            outputVector[index] = Math.Tanh(input[index]);
        }

        return outputVector;
    }
}

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