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6726 :: How to write multi-line sugar => and sugar do?

• alexeypetrushin (orginal) [2020-08-25T01:23:35+02:00] view original

  I'm trying to write map_csv function, so that if you provide it a CSV file name and a function how to convert row to Object it would return list of such Objects.

  
  import strformat, sugar
  
  proc map_csv[T](
    csv_file_path: string,
    map: (
      row: (key: string) -> string
    ) -> T
  ): seq[T] =
    for i in 1..3:
      result.add map(proc (key: string): string = fmt"{key} {i}")
    result
  
  proc load_companies1(): seq[string] =
    map_csv("companies.csv", (row) => row("symbol"))
  
  echo load_companies1()
  Run

  But I can't create multiline proc with sugar

  
  proc load_companies2(): seq[string] =
    map_csv("companies.csv", (row) =>
      # How to specify multiline?
      let v = row("symbol")
      v
    )
  echo load_companies2()
  Run

  And also exprimental do with sugar and type infer

  
  proc load_companies3(): seq[string] =
    map_csv("companies.csv") do row
      let v = row("symbol")
      v
  echo load_companies3()
  Run

  Is there a way to do that?

  P.S.

  Also, sugar seems to fail to infer this line result.add map(proc (key: string): string = fmt"{key} {i}") - could it be inferred?

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• shirleyquirk (orginal) [2020-08-25T01:40:13+02:00] view original

  Multiline lambdas: Use a proc or a block:

  proc load_companies2(): seq[string] =
    map_csv("companies.csv", (row) => block:
      let v = row("symbol")
      v
    )
  Run

  Or the verbose way

  proc load_companies2(): seq[string] =
    map_csv("companies.csv", proc(row:(string)->string):string =
      let v = row("symbol")
      v
    )
  echo load_companies2()
  Run

---

• alexeypetrushin (orginal) [2020-08-25T01:59:34+02:00] view original

  Thanks, but seems like it's not compiling..., do I miss something?

  
  import strformat, sugar
  
  proc map_csv[T](
    csv_file_path: string,
    map: (
      row: (key: string) -> string
    ) -> T
  ): seq[T] =
    for i in 1..3:
      result.add map(proc (key: string): string = fmt"{key} {i}")
    result
  
  
  proc load_companies2(): seq[string] =
    map_csv("companies.csv", (row) => block:
      let v = row("symbol")
      v
    )
  Run

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