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9762 :: Strange error: single character string constants

• freeflow (orginal) [2022-12-26T13:39:54+01:00] view original

  I have defined some single character string constants which sit in their own 'chars.nim' file.

  
  const    twHat*                  : string = "^"
  const    twBar*                  : string = "|"
  const    twComma*                : string = ","
  const    twPeriod*               : string = "."
  const    twSpace*                : string = " "
  const    twHyphen*               : string = "-"
  const    twColon*                : string = ":"
  const    twSemiColon*            : string = ";"
  const    twHash*                 : string = "#"
  const    twPlus*                 : string = "+"
  const    twAsterix*              : string = "*"
  const    twLParen*               : string = "("
  const    twRParen*               : string = ")"
  const    twRAngle*               : string = ">"
  
  Run

  When I compile I'm seeing a single error but I cannot work out the cause.

  : used config file 'C:\Users\XXXXXX\.choosenim\toolchains\nim-#devel\config\nim.cfg' [Conf]
  Hint: used config file 'C:\Users\XXXXXX.choosenim\toolchains\nim-#devel\config\config.nims' [Conf]
  .....................................................................................................
  C:\Users\XXXXXXc\source\repos\AdventOfCode\Nim\nim2022\src\chars.nim(25, 45) Error: type mismatch: got 'string' for '"#"' but expected 'char'
  
  Run

  output of nim -v is

  
  Nim Compiler Version 1.9.1 [Windows: amd64]
  Compiled at 2022-12-25
  Copyright (c) 2006-2022 by Andreas Rumpf
  
  active boot switches: -d:release
  Run

  Please note that I am an extreme novice when it comes to setting up VSCode for working with nim.

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• Araq (orginal) [2022-12-26T14:33:18+01:00] view original

  Single character constants would look like:

  const twHat*: char = '^'
  
  Run

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• DeletedUser (orginal) [2022-12-26T14:39:39+01:00] view original

  Is the error really in the code that you gave? What is line 25?

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• freeflow (orginal) [2022-12-26T16:21:13+01:00] view original

  Thanks for the reply. As you can surmise this is an Advent of Code problem. My original solutions were written in the new twinBasic dialect of VBA. I have a simple VBA macro that does some search and replaces which gets VBA/twinBasic code to 90% nim syntax.

  twinBasic/VBA doesn't have char Types hence the single character strings. I actually implemented your proposal before reading the above and all works as it should.

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• freeflow (orginal) [2022-12-26T16:24:04+01:00] view original

  The line is

  
  const    twHash*                 : string = "#"
  Run

  but as you can see from my response to Araq I've since converted the single character strings to chars and now don't see any errors.a

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• shirleyquirk (orginal) [2022-12-26T20:07:01+01:00] view original

  I have a simple VBA macro that does some search and replaces which gets VBA/twinBasic code to 90% nim syntax.

  Nim 3.0 just dropped

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• fxn (orginal) [2022-12-26T20:14:52+01:00] view original

  Regardless of what is a good practice for single-char constants, that code should compile and client code should be able to work with those strings. There should be something else triggering that error.

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• planetis (orginal) [2022-12-26T20:19:40+01:00] view original

  Obviously OP confuses single quotes with double this line gives the exact error:

  const    twHash*                 : char = "#"
  Run

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• DeletedUser (orginal) [2022-12-26T20:57:06+01:00] view original

  Pretty sure what happened is constant folding folded the constant into a string where a char was expected, but the line information of the original constant was kept so the error showed at the constant definition. So I agree this is probably misleading error information, but this is speculation based off of invisible code

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• freeflow (orginal) [2022-12-26T22:50:00+01:00] view original

  Apologies if I'm sowing confusion. I'm just a complete amateur programmer looking for something to test solutions when VBA/twinBasic takes too long or has memory issues. Nim seemed to fit the bill really well, especially as the syntax allows an almost 1:1 mapping from VBA to nim. I just have to remember that VBA passes parameters by reference and nim by value. It causes some entertainment (late night frustration) on occasion.

  This was the original file that was leading to the error message when I it was imported as '../../AoCLib/chars'. There are two blank lines before the first line below.

  
  
  #    \r, \c	carriage return
  #\n, \l	line feed
  #\f	form feed
  #\t	tabulator
  #\v	vertical tabulator
  #\\	backslash
  #\"	quotation mark
  #\'	apostrophe
  #\ '0'..'9'+	character with decimal value d; all decimal digits directly following are used for the character
  #\a	alert
  #\b	backspace
  #\e	escape [ESC]
  #\x HH	character with hex value HH; exactly two hex digits are allowed
  const    twNoString*             : string = ""
  const    twHat*                  : string = "^"
  const    twBar*                  : string = "|"
  const    twComma*                : string = ","
  const    twPeriod*               : string = "."
  const    twSpace*                : string = " "
  const    twHyphen*               : string = "-"
  const    twColon*                : string = ":"
  const    twSemiColon*            : string = ";"
  const    twHash*                 : string = "#"
  const    twPlus*                 : string = "+"
  const    twAsterix*              : string = "*"
  const    twLParen*               : string = "("
  const    twRParen*               : string = ")"
  const    twRAngle*               : string = ">"
  const    twLAngle*               : string = "<"
  const    twAmp*                  : string = "@"
  const    twLBracket*             : string = "["
  const    twRBracket*             : string = "]"
  const    twLCurly*               : string = "{"
  const    twRCurly*               : string = "}"
  const    twPlainDQuote*          : string = "\""
  const    twPlainSQuote*          : string = "'"
  const    twLSmartSQuote*         : string = "‘" #ChrW$(145)   ' Alt+0145
  const    twRSmartSQuote*         : string = "’" #ChrW$(146)   ' Alt+0146
  const    twLSMartDQuote*         : string = "“" #ChrW$(147)   ' Alt+0147
  const    twRSmartDQuote*         : string = "”" #ChrW$(148)   ' Alt+0148
  const    twTab*                  : string = "\t"
  const    twCrLf*                 : string = "\r\n"
  const    twLf*                   : string = "\n"
  const    twCr*                   : string = "\c"
  const    twNBsp*                 : string = "\255" #Chr$(255)
  Run

  which came from the VBA file

  
  Public Const twHat                  As string = "^"
  Public Const twEqual                As string = "="
  Public Const twLArrow               As string = "<"
  Public Const twRArrow               As string = ">"
  Public Const twNoString             As String = ""
  Public Const twBar                  As String = "|"
  Public Const twComma                As String = ","
  Public Const twPeriod               As String = "."
  Public Const twSpace                As String = " "
  Public Const twHyphen               As String = "-"
  Public Const twColon                As String = ":"
  Public Const twSemiColon            As String = ";"
  Public Const twHash                 As String = "#"
  Public Const twPlus                 As String = "+"
  Public Const twAsterix              As String = "*"
  Public Const twLParen               As String = "("
  Public Const twRParen               As String = ")"
  Public Const twAmp                  As String = "@"
  Public Const twLBracket             As String = "["
  Public Const twRBracket             As String = "]"
  Public Const twLCurly               As String = "{"
  Public Const twRCurly               As String = "}"
  Public Const twBSlash               As string = "\"
  Public Const twFSlash               As string = "/"
  Public Const twPlainDQuote          As String = """"
  Public Const twPlainSQuote          As String = "'"
  Public Const twLSmartSQuote         As String = "‘" 'ChrW$(145)   ' Alt+0145
  Public Const twRSmartSQuote         As String = "’" 'ChrW$(146)   ' Alt+0146
  Public Const twLSMartDQuote         As String = "“" 'ChrW$(147)   ' Alt+0147
  Public Const twRSmartDQuote         As String = "”" 'ChrW$(148)   ' Alt+0148
  Public Const twTab                  As String = vbTab
  Public Const twCrLf                 As String = vbCrLf
  Public Const twLf                   As String = vbLf
  Public Const twCr                   As String = vbCr
  Public Const twNBsp                 As String = "ÿ" 'Chr$(255)
  Run

  I have continued editing /plating since the original post and currently I'm seeing

  
  const SOUTH                                    : string = "v"
  Run

  with the "v" highlighted as an error with the error message

  
  type mismatch: got 'string' for '"v"' but expected 'char'
  Run

  If it helps, I really quite like nim.

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• RodSteward (orginal) [2022-12-26T23:11:50+01:00] view original

  What happens when you replace

  const    twHash*                 : string = "#"
  Run

  with

  const    twHash*                 : string = "\xHH"  # HH = ASCII value of #
  Run

  ?

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• DeletedUser (orginal) [2022-12-27T10:21:34+01:00] view original

  Again, the error is likely happening in the context where you use the constant SOUTH, Nim is just giving incorrect line information for the error. We could fix this issue but it would be nice to know the exact context

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• freeflow (orginal) [2022-12-27T11:05:49+01:00] view original

  I think I've located the cause of the issue.

  The constants

  
  const WALL                                     : string = twHat
  const PATH                                     : string = twPeriod
  const EAST                                     : string = twLAngle
  const WEST                                     : string = twRAngle
  const NORTH                                    : string = twHat
  const SOUTH                                    : string = "v"
  Run

  are used in a single location to convert strings to set of x,y coordinates.

  the problem test data set is

  
  #E######
  #>>.<^<#
  #.<..<<#
  #>v.><>#
  #<^v^^>#
  ######.#
  Run

  myData is a seq of strings representing the above dataset this dataset is converted to sets of x,y coordinates using

  
  s.FinalXY = (myData.first.find(twHash),myData.low)
      s.Current = (myData.last.find(twHash),myData.high)
      
      for myRow in s.MinRow..s.MaxRow:
          for myCol in s.MinCol..s.MaxCol:
  ****            let myChar: char =  $mydata[myRow][myCol] *****
              case myChar
                  of WALL:
                      s.Wall.add((myCol, myRow))
                  of NORTH:
                      s.NorthB.add((myCol, myRow))
                  of SOUTH:
                      s.SouthB.add((myCol, myRow))
                  of WEST:
                      s.WestB.add((myCol, myRow))
                  of EAST:
                      s.EastB.add((myCol, myRow))
                  else:
                      discard
  Run

  the line highlighted with **** had been giving me an error at the [mycol] when myChar was defined as string, so I'd changeed it to char which leads to a mismatch between the constant declarations and the case variable. type.

  changing

  
  let myChar: char =  mydata[myRow][myCol]
  Run

  to

  
  let myChar: string =  $mydata[myRow][myCol]
  Run

  resolves the problem with twHash but now leaves me with an error of '

  
  C:\Users\xxxxx\source\repos\AdventOfCode\Nim\AoCLib\src\chars.nim(20, 45) Error: duplicate case label
  Run

  which is the line

  
  const twHat                  : string = "^"
  Run

  If I rewrite the case statement using the tw strings directly

  
      for myRow in s.MinRow..s.MaxRow:
          for myCol in s.MinCol..s.MaxCol:
              let myChar: string =  $mydata[myRow][myCol]
              case myChar
                  of twHash:
                      s.Wall.add((myCol, myRow))
                  of twHat:
                      s.NorthB.add((myCol, myRow))
                  of "v":
                      s.SouthB.add((myCol, myRow))
                  of twLAngle:
                      s.WestB.add((myCol, myRow))
                  of twRAngle:
                      s.EastB.add((myCol, myRow))
                  else:
                      discard
  Run

  All errors go away and I get a successful compile.

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• DeletedUser (orginal) [2022-12-27T11:15:46+01:00] view original

  If you remove the $ from myChar: char = $mydata[myRow][myCol] and convert the constants to chars as well, it should work.

  Thanks for giving information about this issue, the confusing error message should be fixed with https://github.com/nim-lang/Nim/pull/21182

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• PMunch (orginal) [2022-12-27T15:08:15+01:00] view original

  By the way, in Nim it would be good practice to define groups of constants like these as enums. Make it possible to write type safe procedures that accept a sub-set of your constants.

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• freeflow (orginal) [2022-12-27T16:30:48+01:00] view original

  Indeed, I continue to explore how nim can be used better. I now have those single character string defined as chars and am experimenting with

  
  type
      direction = enum
          North = (0,  $twHat)
          East = (1, $twRAngle
          South = (2, "v")
          West = (3, $twLAngle)
  Run

  and I've moved the individual blizzard seq into a Table

  
  s.Blizzards=[$North: newSeq[Point](), $East: newSeq[Point], $South; newSeq[Point](), $West: newSeq[Point}()}.toTable
  Run

  which is working well, although I couldn't understand why

  
  s.Blizzards = {$North; @[], $East:  @[], $South: @[],  $West: @[]}.toTable
  Run

  refused to compile even though s.Blizzards has been assigned the Type of Table[string, seq[Point]]

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• SolitudeSF (orginal) [2022-12-27T22:58:48+01:00] view original

  @[] doesnt have definite type and there are too many indirection for compiler to infer it.

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