C is also a functional programming language

Why not? I can just avoid side-effects. I can also treat functions as first-order data using Function pointers.

>>17
No - that's not the logic OP was using at all. Transforming a program
from C to Haskell via Turing Completeness says absolutely nothing
about the style of programming used to create the original C
program. Furthermore, OP (and others since) have made valid points
about viability of using functional programming with C, and these
points cannot be transferred to an arbitrary language like
BASIC or Brainfuck through Turing Completeness.