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F # Expression Semantics

Can anyone describe this F # expression for me?

val augment: GameGrid -> points -> unit

What does the keyword mean val

?

Is it true that a function that returns a specified type usually indicates? So, it points to a function that returns a function that returns the specified type? type -> type

type -> type -> type

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(the 'val' bit is not an expression, because I believe it can appear in three different contexts:

  • FSI (F # interactive REPL) output describing the intended binding type
  • in a signature file (.fsi) describing the value type of the associated module
  • in a struct / class definition ("explicit" syntax) to define an instance variable

and none of these are technically the context of the expression.)

As for the type, indeed



A1 -> A2 -> R

means a function that takes A1 and returns a function that takes A2 and returns R. The arguments are curried and you might find it helpful to read eg.

F # function types: fun with tuples and currying

which describes currying and partial application in more detail.

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How did you get this result? FSI?

Val simply indicates the definition of a value.

eg. if you wrote the following in c #

private void Foo(int i);

you have to write this in F #

val Foo : int -> unit


Relatively type -> type -> type

: This is a function with two (type) parameters returning `type '

eg.

let plus a b = a + b

has a signature int -> int -> int

.

Your idea with a function returning a function is indeed correct. This is a very interesting technique in many functional languages ​​called currying

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