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2523 :: Generating a const by a proc -- unexpected result

• Stefan_Salewski (orginal) [2016-09-08T13:10:11+02:00] view original

  I was cleaning up my chess game, which includes replacing var default values by consts generated at compile time.

  For the code below output of echo is zero for all values, while I expected low(int16). What may be wrong?

  const
    MaxDepth = 15
  
  const
    InvalidScore = low(int16)
  
  type
    Guide = tuple
      v: int16
      si:int8
      di:int8
    
    HashLine = array[-MaxDepth..MaxDepth, Guide]
    
    HashResult = tuple
      age: int # set to zero for last access, increase for each played move
      score: HashLine # exact values
      floor: HashLine # lower bounds
  
  proc genHashResultAllZeroConst: HashLine =
    for i in mitems(result): i.v = InvalidScore
  
  const
    HashResultAllZero = genHashResultAllZeroConst()
  
  proc initHR(hr: var HashResult) =
    hr.age = 0
    hr.score = HashResultAllZero
    hr.floor = HashResultAllZero
    for i in -15..15:
      echo hr.score[i].v
      echo hr.floor[i].v
  
  var hr: HashResult
  initHr(hr)
  Run

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• OderWat (orginal) [2016-09-08T14:12:11+02:00] view original

  I guess it is a compiler bug.

  proc genHashResultAllZeroConst: HashLine =
    for i in mitems(result):
      i.v = InvalidScore
      echo i.v
    echo result.repr
  
  const
    HashResultAllZero = genHashResultAllZeroConst()
  Run

  does show low(int16) on the echo in the loop but the echo afterwards shows an empty array. This behavior changes if HashResultAllZero is changed from const to let. So mitems() does not seem to really work here.

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• wiffel (orginal) [2016-09-08T14:30:08+02:00] view original

  I guess it is a compiler bug. ... So mitems() does not seem to really work here.

  I think so too. The following seems to work OK:

  proc genHashResultAllZeroConst: HashLine =
    for ix in result.low .. result.high:
      result[ix].v = InvalidScore
  Run

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• Stefan_Salewski (orginal) [2016-09-08T19:18:44+02:00] view original

  Thanks.

  Should I add that example to Nim's github issue tracker?

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