You are currently looking at the v6.0 - v8.2 docs (Reason v3.6 syntax edition). You can find the latest API docs here.
(These docs cover all versions between v3 to v8 and are equivalent to the old BuckleScript docs before the rebrand)
List
Provide utilities for list.
t
REtype t('a) = list('a);
length
RElet length: t('a) => int;
cons
RElet cons: ('a, t('a)) => t('a);
isEmpty
RElet isEmpty: t('a) => bool;
hd
RElet hd: t('a) => option('a);
tl
RElet tl: t('a) => option(t('a));
nth
RElet nth: (t('a), int) => option('a);
revAppend
RElet revAppend: (t('a), t('a)) => t('a);
rev
RElet rev: t('a) => t('a);
mapRev
RElet mapRev: ((. 'a) => 'b, t('a)) => t('b);
map
RElet map: ((. 'a) => 'b, t('a)) => t('b);
iter
RElet iter: ((. 'a) => unit, t('a)) => unit;
iteri
RElet iteri: ((. int, 'a) => unit, t('a)) => unit;
foldLeft
RElet foldLeft: ((. 'a, 'b) => 'a, 'a, list('b)) => 'a;
Application order is left to right, tail-recurisve.
foldRight
RElet foldRight: ((. 'a, 'b) => 'b, list('a), 'b) => 'b;
Application order is right to left, tail-recursive.
flatten
RElet flatten: t(t('a)) => t('a);
filter
RElet filter: ((. 'a) => bool, t('a)) => t('a);
filterMap
RElet filterMap: ((. 'a) => option('b), t('a)) => t('b);
countBy
RElet countBy: ((. 'a) => bool, list('a)) => int;
init
RElet init: (int, (. int) => 'a) => t('a);
toVector
RElet toVector: t('a) => Js_vector.t('a);
equal
RElet equal: ((. 'a, 'a) => bool, list('a), list('a)) => bool;