import std.math;

import std.format : format;

​

void main() {

    // Contract on virtual function in interface. Gives garbage as value.

    new SoftPlus1().executeFunction(1E10f); // AssertError: Activation function returned inf for input 5.89038752206e-39.

    // Contract on implementing function. Works as expected.

    new SoftPlus2().executeFunction(1E10f); // AssertError: Activation function returned inf for input 10000000000.

    // Contract on virtual function in abstract class. Works as expected.

    new SoftPlus3().executeFunction(1E10f); // AssertError: Activation function returned inf for input 10000000000.

}

​

interface ActivationFunction1 {

    float executeFunction(float value)

    out (result) {

        assert(result.isFinite, format!"Activation function returned %s for input %.12g."(result, value));

    }

}

​

class SoftPlus1 : ActivationFunction1 {

    override float executeFunction(float value) {

        return log(1 + exp(value));

    }

}

​

interface ActivationFunction2 {

    float executeFunction(float value);

}

​

class SoftPlus2 : ActivationFunction2 {

    override float executeFunction(float value)out (result) {

        assert(result.isFinite, format!"Activation function returned %s for input %.12g."(result, value));

    }

    body { 

        return log(1 + exp(value));

    }

}

​

abstract class ActivationFunction3 {

    float executeFunction(float value)

    out (result) {

        assert(result.isFinite, format!"Activation function returned %s for input %.12g."(result, value));

    }

    body {

        throw new Exception("");

    }

}

​

class SoftPlus3 : ActivationFunction3 {

    override float executeFunction(float value) {

        return log(1 + exp(value));

    }

}

​

​