make_recursion_case: Construct a test for a case in the recursion
Description
This function creates an if-statement for testing if a case can be
applied.
Usage
make_recursion_case(test_expr, value_expr, continue)
Arguments
test_expr
The expression that must be true for the case to be applied
value_expr
The value to compute if the test is true
continue
The next case to check if this one isn't true
Value
An if-statement for checking and potentially evaluating one case.