Question

I have a string array lines, for example

lines = [| "hello"; "world" |]

I’d like to make a string line that concatenates the elements in lines with “code=” string prepended. For example, I need to get the string code="helloworld" from the lines array.

I could get the concatenated string with this code

let concatenatedLine = lines |> String.concat "" 

And I tested this code to prepend “code=” string as follows, but I got error FS0001: The type 'string' is not compatible with the type 'seq<string>' error.

let concatenatedLine = "code=" + lines |> String.concat "" 

What’s wrong with this?

Answer 1

+ binds stronger than |>, so you need to add some parentheses:

let concatenatedLine = "code=" + (lines |> String.concat "")

Otherwise the compiler parses the expression like:

let concatenatedLine = (("code=" + lines) |> (String.concat ""))
                         ^^^^^^^^^^^^^^^
                         error FS0001