Belt.Option
Utilities for option data type.
Utilities for option data type
val keepU : 'a option -> ('a -> bool) Js.Fn.arity1 -> 'a option
Uncurried version of keep
keep optionValue p
If optionValue
is Some value
and p value = true
, it returns Some value
; otherwise returns None
keep (Some 10)(fun x -> x > 5);; (* returns [Some 10] *)
keep (Some 4)(fun x -> x > 5);; (* returns [None] *)
keep None (fun x -> x > 5);; (* returns [None] *)
val forEachU : 'a option -> ('a -> unit) Js.Fn.arity1 -> unit
Uncurried version of forEach
forEach optionValue f
If optionValue
is Some value
, it calls f value
; otherwise returns ()
forEach (Some "thing")(fun x -> Js.log x);; (* logs "thing" *)
forEach None (fun x -> Js.log x);; (* returns () *)
getExn optionalValue
Returns value
if optionalValue
is Some value
, otherwise raises getExn
getExn (Some 3) = 3;;
getExn None (* Raises getExn error *)
getUnsafe x
returns x This is an unsafe operation, it assumes x is neither not None or (Some (None .. ))
val mapWithDefaultU : 'a option -> 'b -> ('a -> 'b) Js.Fn.arity1 -> 'b
Uncurried version of mapWithDefault
mapWithDefault optionValue default f
If optionValue
is Some value
, returns f value
; otherwise returns default
mapWithDefault (Some 3) 0 (fun x -> x + 5) = 8;;
mapWithDefault None 0 (fun x -> x + 5) = 0;;
val mapU : 'a option -> ('a -> 'b) Js.Fn.arity1 -> 'b option
Uncurried version of map
map optionValue f
If optionValue
is Some value
, returns Some (f value)
; otherwise returns None
map (Some 3) (fun x -> x * x) = (Some 9);;
map None (fun x -> x * x) = None;;
val flatMapU : 'a option -> ('a -> 'b option) Js.Fn.arity1 -> 'b option
Uncurried version of flatMap
flatMap optionValue f
If optionValue
is Some value
, returns f value
; otherwise returns None
The function f
must have a return type of 'a option
let f (x : float) =
if x >= 0.0 then
Some (sqrt x)
else
None;;
flatMap (Some 4.0) f = Some 2.0;;
flatMap (Some (-4.0)) f = None;;
flatMap None f = None;;
getWithDefault optionalValue default
If optionalValue
is Some value
, returns value
, otherwise default
getWithDefault (Some 1812) 1066 = 1812;;
getWithDefault None 1066 = 1066;;
orElse optionalValue otherOptional
If optionalValue
is Some value
, returns Some value
, otherwise otherOptional
orElse (Some 1812) (Some 1066) = Some 1812;;
orElse None (Some 1066) = Some 1066;;
orElse None None = None;;
val eqU : 'a option -> 'b option -> ('a -> 'b -> bool) Js.Fn.arity2 -> bool
Uncurried version of eq
eq optValue1 optvalue2 predicate
Evaluates two optional values for equality with respect to a predicate function.
If both optValue1
and optValue2
are None
, returns true
.
If one of the arguments is Some value
and the other is None
, returns false
If arguments are Some value1
and Some value2
, returns the result of predicate value1 value2
; the predicate
function must return a bool
let clockEqual = (fun a b -> a mod 12 = b mod 12);;
eq (Some 3) (Some 15) clockEqual = true;;
eq (Some 3) None clockEqual = false;;
eq None (Some 3) clockEqual = false;;
eq None None clockEqual = true;;
val cmpU : 'a option -> 'b option -> ('a -> 'b -> int) Js.Fn.arity2 -> int
Uncurried version of cmp
cmp optValue1 optvalue2 comparisonFcn
Compares two optional values with respect to a comparison function
If both optValue1
and optValue2
are None
, returns 0.
If the first argument is Some value1
and the second is None
, returns 1 (something is greater than nothing)
If the first argument is None
and the second is Some value2
, returns -1 (nothing is less than something)
If the arguments are Some value1
and Some value2
, returns the result of comparisonFcn value1 value2
; comparisonFcn
takes two arguments and returns -1 if the first argument is less than the second, 0 if the arguments are equal, and 1 if the first argument is greater than the second.
let clockCompare = fun a b -> compare (a mod 12) (b mod 12);;
cmp (Some 3) (Some 15) clockCompare = 0;;
cmp (Some 3) (Some 14) clockCompare = 1;;
cmp (Some 2) (Some 15) clockCompare = -1;;
cmp None (Some 15) clockCompare = -1;;
cmp (Some 14) None clockCompare = 1;;
cmp None None clockCompare = 0;;