PROGRAMMING CHALLENGE

This one should be difficult enough for you guys,

Write a function foo that takes a number n and returns a function that takes a number i, and returns n incremented by i.


My submission, in Scheme


(define (foo num)
  (lambda (x) (+ x num)))

>>4
1) would work, except it's more complicated than you make it seem; for instance malloc'd memory is execution-protected on modern operating systems. Honestly to make it portable, your best bet is probably to compile it with llvm. You still have to manage the memory containing the closure though, so it's still not like a closure in a typical HLL.

2) does not work because your funcall macro can't be passed around as a function pointer. there's no real way to do it other than return a struct (the closing environment) and pass in that struct in the function call.

In other words it's certainly not possible in standard C, but possible with runtime code generation or compiler extensions.