# RapidMiner

## Why is this error?

Regular Contributor

# Why is this error?

Hi,

If I run the below code, i get an error corresponding to the enclosed brackets ( or [. But the formulas are correct.

`<operator name="Root" class="Process" expanded="yes">    <operator name="ExampleSetGenerator" class="ExampleSetGenerator">        <parameter key="target_function"	value="random"/>        <parameter key="number_examples"	value="10"/>    </operator>    <operator name="Real2Integer" class="Real2Integer">        <parameter key="round"	value="true"/>    </operator>    <operator name="AttributeAggregation" class="AttributeAggregation">        <parameter key="attribute_name"	value="max"/>        <parameter key="aggregation_attributes"	value="att.*"/>        <parameter key="aggregation_function"	value="maximum"/>    </operator>    <operator name="FeatureIterator" class="FeatureIterator" expanded="yes">        <parameter key="filter"	value="att.*"/>        <parameter key="iteration_macro"	value="loo"/>        <parameter key="work_on_input"	value="false"/>        <operator name="AttributeConstruction" class="AttributeConstruction">            <list key="function_descriptions">              <parameter key="try_%{loo}"	value="(%{loo}-max)^2"/>            </list>        </operator>    </operator></operator>`

Why is the error?

If I change the formula as "(%{loo}-1)^2" in the AttributeConstruction operator, there is no error.

What exactly is happening?