# MIT License, Copyright (c) 2022 Marvin Borner

:import std/Combinator .

# empty option
none T

# encapsulates value in option
some [[[0 2]]]

# checks whether option is none
none? [0 T [F]]
:test (none? none) (T)
:test (none? (some [[0]])) (F)

# checks whether option is some
some? [0 F [T]]
:test (some? none) (F)
:test (some? (some [[0]])) (T)

# applies a function to the value in option
map [[0 none [some (2 0)]]]
:test (map [[1]] (some [[0]])) (some [[[0]]])
:test (map [[1]] none) (none)

# applies a function to the value in option or returns first arg if none
map-or [[[0 2 1]]]
:test (map-or [[[2]]] [[1]] (some [[0]])) ([[[0]]])
:test (map-or [[[2]]] [[1]] none) ([[[2]]])

# extracts value from option or returns first argument if none
unwrap-or [[0 1 I]]
:test (unwrap-or F (some T)) (T)
:test (unwrap-or F none) (F)

# applies encapsulated value to given function
apply [[1 none 0]]
:test (apply none [some ([[1]] 0)]) (none)
:test (apply (some [[0]]) [some ([[1]] 0)]) (some [[[0]]])