MLem
Meta Language Extensions and Manipulation
Syntax
Whole program is a big expression, use parentheses to avoid ambiguities.
letbinding
let name = value; expression
- Function apply — functions have only one parameter
inc 2
- Lambda abstraction
\x -> x
- Pattern matching
match exp with
| case -> value
| _ -> fallback
-
Data Types
- Numeric integer literal
number - Tuples
(a,b,...) - String literal, between
""
- Numeric integer literal
-
Custom Types:
type Boolean = true | false;
type MaybeTwo = Just of number * number | Nothing;
Use Y Combinator for recursion (native recursion not yet supported).
Example program
type Boolean = true | false;
type MaybeTwo = Just of number * number | Nothing;
let Y = \f -> ((\x -> (x x)) (\y -> (f (\x -> ((y y) x)))));
let sub = \x -> \y -> (sum x (neg y));
let fibonacci = Y (\f -> \x ->
match x with
| 0 -> 0
| 1 -> 1
| x -> (
let a = (sub x) 1;
let b = (sub x) 2;
let fa = f a;
let fb = f b;
sum fa fb
)
);
match (fibonacci 8) with
| 21 -> true
| _ -> false
Usage
Place your code in test.mml.
yarn install
yarn start
Rebuild grammar
yarn build
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