How do I have multiple generators for list comprehensions in F#?

I am trying to write something 开发者_开发百科like this

[(x,y)|x<- [1,2,3], y <- [’a’,’b’]]
 => [(1,’a’),(1,’b’),(2,’a’),(2,’b’),(3,’a’),(3,’b’)]

[for x in [1;2;3] do
 for y in ['a';'b'] do
 yield x,y]

just another fun way

[1;2;3] |> List.map ( fun X -> ['a';'b'] |> List.map (fun A -> X,A) )

F# equivalent.

List.zip [1;2;3] ['a';'b';'c']