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f#seq

How to extract data from iterating a sequence

csvData1 contains the data in a .csv file. I've created a sequence out of just two of the columns in the spreadsheet ("GIC-ID", "COVERAGE DESCRIPTION")

let mappedSeq1 = 
   seq { for csvRow in csvData1 do yield (csvRow.[2], csvRow.[5]) }

Looking in the Visual Studio debugger x winds up being a System.Tuple<string,string>.

for x in mappedSeq1 do
    printfn "%A" x
    printfn "%A" x.ToString

Here is the result of executing

for x in mappedSeq1

("GIC-ID", "COVERAGE DESCRIPTION")
<fun:main@28>

I am having difficulty figuring out how to access x, so I can extract the first element.

Solution

  • You can use pattern matching to deconstruct the tuple

    for (a, b) in mappedSeq1 do
  // ...

    or

    for x in mappedSeq1 do
  let a, b = x

    Alternatively for a 2-tuple you can use the built-in function fst and snd