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10107 :: += operator with if statement gives errors

• freeflow (orginal) [2023-04-17T14:41:59+02:00] view original

  I'd appreciate a pointer as to why I'm getting two errors for this line of code one for the + in += One for 'if myMoves == UP: 1 else: -1'

  
  myFloor += if myMoves == UP: 1 else: -1
  
  Run

  myfloor is defined as int, myMoves is derived from 'for myMoves in s.data' where s.data is a string and UP is '('

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• Jaap (orginal) [2023-04-17T14:53:32+02:00] view original

  myFloor += (if myMoves == UP: 1 else: -1) will work

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• cblake (orginal) [2023-04-17T15:27:31+02:00] view original

  This also works (with or without parens):

  inc myFloor, if myMoves == UP: 1 else: -1
  Run

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• freeflow (orginal) [2023-04-17T21:59:48+02:00] view original

  Thanks for the feedback, the suggestions give me a workaround. But I'm still interested in understanding the Why

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• planetis (orginal) [2023-04-17T23:42:21+02:00] view original

  From my limited understanding, I would guess that the parser is having trouble when encountering a if expression as argument to a infix operator. In this case += but I have seen the error with & as well.

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• Araq (orginal) [2023-04-18T08:08:03+02:00] view original

  Read grammar.txt to find out why: A binary expression consists of primary expressions and their definition is:

  
  primary = simplePrimary (commandStart expr)
          / operatorB primary
          / routineExpr
          / rawTypeDesc
          / prefixOperator primary
  Run

  which does not include if or case or try expressions. Would it hurt to add these? For this you need to analyse the first and follow sets of the grammar rules. This is tedious to do manually so somebody should patch tools / grammar_nanny.nim to do it automatically. PRs are welcome. ;-)

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