CODEWITHSUNDEEP
f#
Joseph Caltagirone
Joseph Caltagirone

Reputation: 41

F# recursive function exit?

I am very new to F# programming. I am looking for an answer as to why the following recursive function will exit when the n=0 condition is reached. Does the "then 1" syntax have a special meaning that equates to EXIT?

let rec factorial n = 
    if n = 0 
    then 1 
    else n * factorial (n - 1)

Upvotes: 4

Views: 480

Answers (1)

TheQuickBrownFox
TheQuickBrownFox

Reputation: 10624

Functional programming languages are expression oriented, as opposed to statement oriented. This means that everything is an expression that can be evaluated into a value.

The control flow structures, if and match, are also just expressions. The compiler checks that all branches of these expressions return the same type.

If you're familiar with the conditional ternary operator in other languages, F#'s expression if true then 1 else 0, is equivalent to true ? 1 : 0.

Furthermore, the function doesn't "exit" as such. It completes evaluation. Each instance of the function (there will be n + 1 instances) completes evaluation at the end of the if/then/else expression.

Upvotes: 6

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