CODEWITHSUNDEEP
f#
Neo
Neo

Reputation: 908

F#, Split String and .Net methods

I'm new to F#. I'm using VS2008 shell and F# interactive. I try to split a string using "System.String.Split" but then I get the error: "Split is not a static method"

code example:

let Count text =
    let words = System.String.Split [' '] text
    let nWords = words.Length
    (nWords)

How do I use the String methods like split in F# ?

Upvotes: 51

Views: 42231

Answers (4)

Rodrigo Rodrigues
Rodrigo Rodrigues

Reputation: 8556

Others have commented already that String.Split is a method, not a static function.

However, as I mentioned in this other answer here, they recently introduce a new syntax in f#8 for cases like this, so we don't have to write those small and convenient module functions wrapping object members.

It is called _.Property as a shorthand for (fun x -> x.Property), and can be done like this:

let count (text : string) =
  text
  |> _.Split(' ')
  |> Seq.length

There is a limitation though: you can only use this new syntax to replace a lambda that does only an atomic expression, i.e.:

An atomic expression is an expression which has no whitespace unless enclosed in method call parentheses.

That is why, for example, I had to write it like _.Split(' '), as it is atomic. It would have not worked as _.Split ' ' (notice the whitespace before the curried parameter).

Upvotes: 1

sdgfsdh
sdgfsdh

Reputation: 37045

Using .NET member functions:

let count (text : string) =
  text.Split [|' '|]
  |> Seq.length

Or using FSharpx, which gives us more ergonomic free-functions...

paket.dependencies

source https://api.nuget.org/v3/index.json

nuget FSharpx.Extras 2.3.2

paket.references

FSharpx.Extras

Usage: 

open FSharpx

let count (text : string) =
  text
  |> String.splitChar [| ' ' |]
  |> Seq.length

Note that F# Power Pack seems to be deprecated.

Upvotes: 1

1-2-3
1-2-3

Reputation: 69

The function String.split is now defined in the F# Power Pack. You must add 

#r "FSharp.PowerPack.dll";; 
#r "FSharp.PowerPack.Compatibility.dll";;

See the errata for Expert F#: http://www.expert-fsharp.com/Updates/Expert-FSharp-Errata-Jan-27-2009.pdf

Get FSharp.PowerPack.dll here: http://fsharppowerpack.codeplex.com/

Upvotes: 6

itowlson
itowlson

Reputation: 74802

You call them as instance methods:

let Count (text : string) =
  let words = text.Split [|' '|]
  let nWords = words.Length
  (nWords)

(Note you need to use [| |] because Split takes an array not a list; or, as per Joel Mueller's comment, because Split takes a params array, you can just pass in the delimiters as separate arguments (e.g. text.Split(' ', '\n')).)

Upvotes: 62

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