Implements OCaml-style pattern matching and the Cons operator in Python.

See below for examples of using the pattern_match() function:

Example 1

Compute sum of a list

OCaml code:

let sum l =
    match l with
    | [] -> 0
    | h::t -> h + sum t

Python code:

def sum(l):
    return pattern_match(l, [
        ([], 0),
        (Cons(Variable("h", int), Variable("t", list)), Evaluation("h + FUNC(t)"))
    ])

Example 2

Check if consecutive elements el1 and el2 exist in list, with one in between

OCaml code:

let search_two_skip l el1 el2 =
    match l with
    | [] -> false
    | el1::_::el2::t -> true
    | h::t -> search_two_skip t el1 el2

Python code:

def search_two_skip(l, el1, el2):
    return pattern_match(l, [
        ([], False),
        (Cons(el1, Wildcard(), el2, Variable("t", list)), True),
        (Cons(Variable("h", list_type), Variable("t", list)), Evaluation("FUNC(t)"))
    ])

Currently implemented examples

(see line 154 onwards in pattern_match.py for implementations)

• next_highest_odd: obtains next highest odd number
• fib: gets specified fibonacci number
• search: checks if element is in list
• search_two: checks if two consecutive elements are in list
• search_two_skip: checks if two consecutive elements are in list, with one in between
• is_second: checks if element is second in list
• length: length of list
• sum: sum of list of ints
• sum_of_triple: sum of 3-tuple of ints
• is_double: checks if second element of tuple is double the first element

To do

• Deal with eval()'s incompatibility with list of strings
• Add warning system for unreachable patterns