math : add
DESCRIPTION
<add> increments a user variable by the given value.
Note that if <add> is used with a variable which is a string, the number format will be applied to the variable first. If the variable has no numeric content, this will result in a value of 0. Best practice is to use the number format with the <set> module when setting variables intended to be numeric.
PARAMETERS
var - which variable to operate on
value - (float) the value to add
float - (true|false) whether to store decimal values. True by default. Decimals are always restricted to two places.
EXAMPLES
...
<add var="right_answers" value="1" />
...
<add var="right_answers" value="1" />
...