Bifunctors

Source

github.com/denful/bend

bimap fL fR lens

Map both branches of the lens result.

• fL applied to left; fR applied to right
• set is unchanged (only get transforms)

(bend.bimap (_: "err") (x: x * 2) bend.int).get 5
# right 10

(bend.bimap (_: "err") (x: x * 2) bend.int).get "bad"
# left "err"

lmap f lens

Map left branch only; pass right unchanged.

(bend.lmap (_: "replaced") bend.int).get "bad"
# left "replaced"

(bend.lmap (_: "replaced") bend.int).get 42
# right 42

rmap f lens

Map right branch only; pass left unchanged.

(bend.rmap (x: x + 1) bend.int).get 5
# right 6

(bend.rmap (x: x + 1) bend.int).get "bad"
# left "bad"