<tool name="Calculate numeric parameter value" id="calculate_numeric_param" version="0.1.0" profile="19.05" tool_type="expression">
    <description>from parameters</description>
    <expression type="ecma5.1">
{
    let s = "";
    for (const repeat of $job.components) {
        s += repeat.param_type.component_value
        s += repeat.arith
        if (repeat.arith == "") {
            break;
        }
    };
    let e;
    if ($job.output_type == "integer") {
        e = parseInt(eval(s));
    } else {
        e = eval(s);
    }
    return {'output': e};
}
    </expression>
    <inputs>
        <repeat name="components" min="2">
            <conditional name="param_type">
                <param name="select_param_type" type="select" label="Choose the type of parameter for this field">
                    <option value="integer">Integer Parameter</option>
                    <option value="float">Float Parameter</option>
                </param>
                 <when value="integer">
                    <param name="component_value" value="" type="integer" label="Enter integer for calculating the parameter"/>
                </when>
                 <when value="float">
                    <param name="component_value" value="" type="float" label="Enter float for calculating the parameter"/>
                </when>
            </conditional>
            <param name='arith' type='select' label='Choose the arithmetic operator to apply'>
                <option value="+">Addition (+)</option>
                <option value="-">Subtraction (-)</option>
                <option value="*">Multiplication (*)</option>
                <option value="/">Division (/)</option>
                <option value="**">Exponentiation (**)</option>
                <option value="%">Modulus (%)</option>
                <option value="">None (expression should end here)</option>
            </param>
        </repeat>
        <param name='output_type' type='select' label='Choose whether the output should be an integer or a float.'>
            <option value="integer">Integer</option>
            <option value="float">Float</option>
        </param>
    </inputs>
    <outputs>
        <output type="float" name="float_param" from="output">
            <filter>output_type == 'float'</filter>
        </output>
        <output type="integer" name="integer_param" from="output">
            <filter>output_type == 'integer'</filter>
        </output>
    </outputs>
    <tests>
        <test>
            <repeat name="components">
                <conditional name="param_type">
                    <param name="select_param_type" value="integer"/>
                    <param name="component_value" value="1"/>
                </conditional>
                <param name="arith" value="+"/>
            </repeat>
            <repeat name="components">
                <conditional name="param_type">
                    <param name="select_param_type" value="integer"/>
                    <param name="component_value" value="1"/>
                </conditional>
                <param name="arith" value=""/>
            </repeat>
            <param name="output_type" value="integer"/>
            <output name="output">
                <assert_contents>
                    <has_line line="2"/>
                </assert_contents>
            </output>
        </test>
        <test>
            <repeat name="components">
                <conditional name="param_type">
                    <param name="select_param_type" value="float"/>
                    <param name="component_value" value="1.5"/>
                </conditional>
                <param name="arith" value="*"/>
            </repeat>
            <repeat name="components">
                <conditional name="param_type">
                    <param name="select_param_type" value="float"/>
                    <param name="component_value" value="1.5"/>
                </conditional>
                <param name="arith" value=""/>
            </repeat>
            <param name="output_type" value="float"/>
            <output name="output">
                <assert_contents>
                    <has_line line="2.25"/>
                </assert_contents>
            </output>
        </test>
        <test>
            <repeat name="components">
                <conditional name="param_type">
                    <param name="select_param_type" value="float"/>
                    <param name="component_value" value="1.5"/>
                </conditional>
                <param name="arith" value="*"/>
            </repeat>
            <repeat name="components">
                <conditional name="param_type">
                    <param name="select_param_type" value="float"/>
                    <param name="component_value" value="1.5"/>
                </conditional>
                <param name="arith" value=""/>
            </repeat>
            <param name="output_type" value="integer"/>
            <output name="output">
                <assert_contents>
                    <not_has_text text="2.25"/>
                    <has_line line="2"/>
                </assert_contents>
            </output>
        </test>
    </tests>
    <help><![CDATA[
This tool calculates an output (integer or float) parameter
from integer and float input parameters and specified simple
arithmetic operations (addition, subtraction, multiplication,
division, exponentiation, and modulus).
    ]]></help>
</tool>