[Tutor] Writing the Map function as a oneliner

[Rafael Turner]

Hello,

I am trying to write the map function as a oneliner. I currently have
implement map as a list comprehension:
map = lambda F,li: [F(x) for x in li]

But I would like to make recursive version. Here is what I was thinking:

I can write map as

def pyMap(F,li):
    if li == []:
        return []
    else:
        return [F(li[0])] + map2(F, li[1:])

I can logical encode an if-then-else structure as follows:

Let Q be the result of the following IF,THEN, ELSE conditional structure:

If(S):
      Then: A
Else: B

We can implement this only using logical constructors.

Q = (A AND S) OR (B AND NOT S)

where:

   S is the input for the If condition,
   A is the input to Then subexpression
   B is the input for the Else subexpression
   Q is the output of the entire If-Then-Else expression.

So, I tried:
def pyMap2(F, li):
    def ifFun(P,eq): return li == []
    return ([] and ifFun(li,[])) or ([F(li[0])] + pyMap2(F, li[1:]) and not [])

But it's no use. pyMap works fine but pyMap2 does not.

I saved the above code as map.py and ran it in the interpreter.

>>> import map
>>> map.pyMap2(lambda x: x + 2, [1,2,3])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "map.py", line 15, in pyMap2
    return ([] and fIF(li,[])) or ([F(li[0])] + pyMap2(F, li[1:]) and not [])
  File "map.py", line 15, in pyMap2
    return ([] and fIF(li,[])) or ([F(li[0])] + pyMap2(F, li[1:]) and not [])
  File "map.py", line 15, in pyMap2
    return ([] and fIF(li,[])) or ([F(li[0])] + pyMap2(F, li[1:]) and not [])
  File "map.py", line 15, in pyMap2
    return ([] and fIF(li,[])) or ([F(li[0])] + pyMap2(F, li[1:]) and not [])
IndexError: list index out of range


Thank you for your help,
Rafael