CODEWITHSUNDEEP
f#
Alex Gordon
Alex Gordon

Reputation: 60912

is a function a union or a record type?

Scott has a nice talk about domain modeling in F#, and presents the following slide:

enter image description here

Is the Deal type a record or union type?

My question is regarding this line:

type Deal = Deck -> (Deck*Card)

I'm not sure I understand this. How can we simply create a function and shove it into a type? I thought that the data and functionality are supposed to be separate?

Upvotes: 1

Views: 69

Answers (1)

TeaDrivenDev
TeaDrivenDev

Reputation: 6629

Neither. It's a function type, more precisely it's an alias for the function type described by the signature Deck -> (Deck * Card). The way aliases work is that you can use them to make things clearer wherever you state a type yourself, but if the compiler infers the type, that will always be the original unaliased type.

So in this case, wherever the type Deal is given, any function that takes a Deck and returns a tuple of Deck and Card will be accepted.

Upvotes: 3

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