--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/calculate_numeric_param.xml	Wed May 05 15:03:08 2021 +0000
@@ -0,0 +1,134 @@
+<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>