f# Print if true

Question

Im trying to print the output of function only when it is true but so far all attempts have been unsuccsessful.

Something on the lines of

let printFactor a b =  if b then print_any((a,b))

where b is a boolean and a is an integer. When I try it I get

val printFactor : 'a -> bool -> unit

Any suggestions?

EDIT:

To put things in context im trying to use this with a pipe operator. Lets say I have a function xyz that outputs a list of (int, bool). Id like to do something on these lines

xyz |> printFactor

to print the true values only

Answer 1

You could do e.g. this

let xyz() = [ (1,true); (2,false) ]

let printFactor (i,b) = 
    if b then
        printfn "%A" i

xyz() |> List.iter printFactor

but it would probably be more idiomatic to do, e.g. this

xyz() 
|> List.filter (fun (i,b) -> b) 
|> List.iter (fun (i,b) -> printfn "%d" i)

that is, first filter, and then print.