How does pattern matching work behind the scenes in F#?

Question

I am completely new to F# (and functional programming in general) but I see pattern matching used everywhere in sample code. I am wondering for example how pattern matching actu

Answer 1

No, it doesn't loop. If you have a pattern match like this

match x with
| Foo a b -> a + b
| Bar c -> c

this compiles down to something like this pseudo code:

if (x is a Foo)
  let a = (first element of x) in
  let b = (second element of x) in
  a+b
else if (x is a Bar)
  let c = (first element of x) in
  c

If Foo and Bar are constructors from an algebraic data type (i.e. a type defined like type FooBar = Foo int int | Bar int) the operations x is a Foo and x is a Bar are simple comparisons. If they are defined by an active pattern, the operations are defined by that pattern.