title: Trouble with String.split in F#
body: <p>I am having trouble with the following code, I am trying to build a lexer.</p>
  
  <p>Again I am using the examples from F# for Scientists.</p>
  
  <pre><code>    let lines_of_file filename =
         seq { use stream = File.OpenRead filename
               use reader = new StreamReader(stream)
               while not reader.EndOfStream do
               yield reader.ReadLine() };;
  
      let read_matrix filename =
        lines_of_file filename
        |&gt; Seq.map (String.split [' '])
        |&gt; Seq.map (Seq.map float)
        |&gt; Math.Matrix.of_seq;;
  </code></pre>
  
  <p>I have the following namespaces declared:-</p>
  
  <pre><code>          open System
            open System.IO
            open System.Runtime.Serialization.Formatters.Binary
            open Microsoft.FSharp.Core
  </code></pre>
  
  <p>But in the read_matrix function the "split" in "Split.string" is not recognised. Also the intellisense does not recognise "Matrix".</p>
  
  <p>I have tried declaring a lot of namespaces to see if they recognise the method, but nothing works (my intellisense does not even recognise System.Math).</p>
  
  <p>I apologise if this is a stupid question, I have looked all over MSDN and elsewhere but I could not find anything.</p>
  
  <p>Can anyone help me to get VS to recognise "split" and "Matrix"?</p>
  
  <p>Many thanks.</p>