Bool.Extra

Convenience functions for working with Bools

Basics

all : List Bool -> Bool

All the bools are true.

all [ True, True, True ]
--> True


all [ True, False ]
--> False


all [ False, False ]
--> False


all []
--> True

none : List Bool -> Bool

None of the bools are true.

none [ True, True ]
--> False


none [ True, False ]
--> False


none [ False, False ]
--> True


none []
--> True

any : List Bool -> Bool

At least one of the bools is true.

any [ True, True ]
--> True


any [ True, False ]
--> True


any [ False, False ]
--> False


any []
--> False

notAll : List Bool -> Bool

Not all of them are true

notAll [ True, True ]
--> False


notAll [ True, False ]
--> True


notAll [ False, False ]
--> True


notAll []
--> False

ifElse : a -> a -> Bool -> a

Return the first argument if the given predicate is True. Otherwise, return the second argument.

ifElse "yes" "no" True
--> "yes"


ifElse "yes" "no" False
--> "no"

Predicate

allPass : List (a -> Bool) -> a -> Bool

Determine if all predicates are satisfied by the value.

allPass [ (>) 20, (<) 10 ] 11
--> True


allPass [ (>) 20, (<) 10 ] 21
--> False


allPass [ (>) 20, (<) 10 ] 4
--> False


allPass [] 21
--> True

anyPass : List (a -> Bool) -> a -> Bool

Determine if any predicate is satisfied by the value.

anyPass [ (>) 20, (<) 10 ] 100
--> True


anyPass [ (>) 20, (==) 10 ] 21
--> False


anyPass [] 21
--> False

Maybe

toMaybe : a -> Bool -> Maybe a

Given a value a and a Bool, and wrap a in Just if the Bool is True.

toMaybe 4 True
--> Just 4


toMaybe 4 False
--> Nothing

This kind of function is handy when populating lists..

[ Bool.Extra.toMaybe adminRoute (User.isAdmin user)
, Just dashboardRoute
, Bool.Extra.toMaybe profile (User.isLoggedIn user)
]
    |> List.filterMap identity

..or when generating errors during form validation..

{ field
    | error =
        Bool.Extra.toMaybe FieldIsEmpty (String.isEmpty field.value)
}

String

toString : Bool -> String

Turn a bool into a string

toString True
--> "True"


toString False
--> "False"

fromString : String -> Maybe Bool

Try and extract a Bool from a String

fromString "true"
--> Just True


fromString "False"
--> Just False


fromString "t"
--> Nothing


fromString "My pal foot foot"
--> Nothing

stringDecoder : Decoder Bool

Sometimes webservers will return the unideal json of a string "true" rather than just the native boolean value true. This decoder decodes a string that looks like a Bool, into a Bool

import Json.Decode as Decode
import Json.Encode as Encode


Decode.decodeString stringDecoder "\"true\""
--> Ok True


Decode.decodeString stringDecoder "true"
--> Err (Decode.Failure "Expecting a STRING" (Encode.bool True))

encodeAsString : Bool -> Value

Sometimes in weird unideal circumstances you need to encode True to "true" instead of just true.

import Json.Encode exposing (encode)


encode 0 (encodeAsString True)
--> "\"true\""


encode 0 (encodeAsString False)
--> "\"false\""

Modules

Bool.Extra