Bernie, that looks very good - but my opinion here is worthless! I'm not 
tuned in to all the "NOT" details, not very familiar with PHP, etc.

One other interesting find: I looked through the "help" system on 
PlayRightPro (PDox-DOS), and found "precedence", and... its list is 
exactly as I posted yesterday, but it also has that #$%#$%#$% Unary 
Minus as a separate item in the list, just after the first "()" entry!

Which, IMO, is good news.

So, seems the PDox Exp-Eval code does recognise that special "-", and 
handles it separately. And, presumably the PHP evaluator behaves 
identically?

   - Mike


On 07/09/2017 07:16, Bernie van't Hof wrote:
> What I came up with ..
> 
> public function Parser()
> {
>      $out = '';
>      while ( ! $this->lexer->Eof()) {
>          switch($this->lexer->Next()->type){
>              case whatever:
>                  $out .= $this->Expression();
>          }
>      }
>      return $out;
> }
> 
> public function Expression()
> {
>      $exp = '';
>      do{
>          $exp .= $this->SubExpr();
>      } while ($this->lexer->Peek()->type == 'logical');
>      return $exp;
> }
> private function SubExpr()
> {
>      $exp = '';
>      do{
>          switch($this->Peek()->type){
>              case 'logical':
>                  // PAL's NOT, AND, OR
>                  // use php's && and || instead of AND and OR
>                  // (higher precedence than ops)
>                  $exp .= $this->lexer->Next()->val . '(' . Expression()

> . ')';
>                  break;
>              case 'op':
>                  // PAL's +-*/%=<>
>                  switch($this->lexer->Next()->val)
>                  {
>                      // etc
>                  }
>              //etc (dozens of 'em)
>          }
>      } while($this->lexer->Peek()->type == 'op');
>      return $exp;
> }
> 
> - B
> On 7/9/17 7:54 am, Michael Kennedy wrote:
>> Wow - that's real nasty! But you seem to have resolved it.
>>
>> Back, maybe 20-25 years ago, I recall writing an expression-evaluator 
>> from scratch, and I still recall major hassle with that damn "-" and 
>> with "NOT" - probably the same issue with both. I don't remember the 
>> details, nor good examples, but maybe something like:
>>
>>    A * -B --> A * (-B) --> A * (0-B)
>>
>> So the meaning of each "-" had to be determined first, before deciding 
>> how/when to evaluate it.
>>
>> Maybe the same approach was/is needed for NOT?
>>
>>    - Mike
>>
>>
>> On 06/09/2017 18:56, Bernie van't Hof wrote:
>>> Thanks, Mike.
>>>
>>> What I realised in the mean-time ..
>>>
>>> php has precedence of ! (NOT) above all those on your list except ()
>>> So
>>>      IF NOT Retval = "Esc" ; which works fine
>>> does not become
>>>      if( ! $Retval == 'Esc') // valid php but wrong result!
>>> it should be
>>>      if( ! ($Retval == 'Esc'))
>>>
>>> I used the above pal construct only twice in 30k lines of pal, more 
>>> commonly using
>>>      IF Retval <> "Esc"
>>> which converts nicely to
>>>      if($Retval <> 'Esc')
>>> so I didn't spot it in earlier run-time testing.
>>>
>>>
>>> -B
>>>
>>> On 7/9/17 2:10 am, Michael Kennedy wrote:
>>>> The manuals say:
>>>>   () - Inner pairs first
>>>>   (All the following are Left-to-Right]...
>>>>   * /
>>>>   + -
>>>>   = <> < <= > >=
>>>>   NOT
>>>>   AND
>>>>   OR
>>>>
>>>> ...all as expected...
>>>>
>>>> There's no mention of that darn "unary minus", nor of different 
>>>> contexts of "NOT", etc...
>>>>
>>>> I assume that PDoxDOS represents (1=2), [False], internally as 0, 
>>>> but I don't recall how it represents (1=1) [True, = NOT False]. I  
>>>> think most systems use "-1", but some systems use just "1", and 
>>>> maybe some use "any non-zero value"?.....
>>>>
>>>>    - Mike
>>>>
>>>>
>>>> On 04/09/2017 18:40, Bernie van't Hof wrote:
>>>>> Anyone have handy a operator precedence list for PDOX DOS?
>>>>>
>>>>> Having an issue with 'NOT' and darned if I can see why.
>>>>>
>>>>> Thanks,
>>>>> B