Wednesday, December 3, 2008

"F-dull": F# beginner's mistake... put a space between '-' and a number

I made a very simple mistake while trying to follow the PDC 2008 Intro to F# lecture. "JaredPar" straightened me out about two minutes after I submitted it to . Here is the problem and solution: 
I was trying to code along with the PDC2008 Into to F# video. I get an error in the last line of the code snippet shown below (that the presenter did not get) "Error 1 This value is not a function and cannot be applied". I am running Fsharp- on Visual Studio 2008 shell. The startprice symbol in the last line isunderlined red with same error on mouse over. 
type StockAnalyzer (lprices, days) =
    let prices
|> snd
|> Seq.take days
static member GetAnalyzers (tickers,days) =
|> loadPrices
|> (fun prices -> new  StockAnalyzer (prices, days))
    member s
.Return =
        let  lastPrice
= prices |> Seq.nth 0
        let  startPrice
= prices |> Seq.nth (days - 1)
/ startPrice  -1.
Try putting a space between the "-" and "1". The F# compiler is interpretting -1 as literally a negative value of 1 instead of subtract 1.
Thanks Jaredpar!
The original stackoverflow post is here.

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