// Push a new position scope to track the iteration position
expressionContext.pushPositionScope();
PositionScope pc = expressionContext.getPositionScope();
// Declare an unitialized variable.
InternalExpressionScope scope = (InternalExpressionScope)
expressionContext.getCurrentScope();
Variable variable = scope.declareVariable(variableName);
// Iterate over the sequence.
int length = sequence.getLength();
for (int i = 1; i <= length; i += 1) {