Modify the example in 07-3-gartersnake.rkt to return a set consisting of all the variables that occur undefined at least once in the program.
EXAMPLE: If the GarterSnake program is def f1(x):f2(y) ; f2 is undefined, and y is undefined def f2(x,y): f3(y,x) ; f3 is undefined in the body of f2 def f3 (x,z):f1(f2(z,y),z) ; y is undefined then your function should return a list consisting of the symbols f2, f3, and y in any order.
The program isn't hard; but pay attention to the purpose statements and invariants!
Last modified: Mon Oct 17 16:39:09 Eastern Daylight Time 2016