Opened 4 months ago

Last modified 3 days ago

#2938 accepted defect

The parser for symbolic expressions in infix form parses negative numbers and fractions strangly

Reported by: gkronber Owned by: gkronber
Priority: medium Milestone: HeuristicLab 3.3.16
Component: Problems.DataAnalysis.Symbolic Version: trunk
Keywords: Cc:

Description (last modified by gkronber)

Some examples:

  • Input: -1.0*x + 2.0
  • Expected:
      (+ 
         (* -1.0 x) 
         2.0)
    
  • Output:
    (+ 
      (- (* 1.0 x))
      2.0)
    
  • Input: exp(-1.0*x - 2.0)
  • Output:
    (exp (* 
           -1.0 
           (+ 
             (* 1.0 x) 
             2.0)))
    
  • Expected:
    (exp (- 
           (* -1.0 x)
            2.0))
    
  • Input: 3/3+2/2+1/1
  • Output:
     ((3 * 1/3) + (2 * 1/2) + (1 * 1/1))
    

Change History (4)

comment:1 Changed 3 months ago by gkronber

  • Owner set to gkronber
  • Status changed from new to accepted

comment:2 Changed 3 months ago by gkronber

  • Description modified (diff)
  • Summary changed from The parser for symbolic expressions in infix form parses negative numbers strangly to The parser for symbolic expressions in infix form parses negative numbers and fractions strangly

comment:3 Changed 3 months ago by gkronber

The main problem is that by parsing "-x" as (-1)*x we effectively introduce an additional constant (see non-linear regression). The same issue occurs when parsing "x/y" as "x * 1/y".

Parsing "-3.14" as "(-1)*3.14" is especially strange.

comment:4 Changed 3 days ago by gkronber

  • Version set to trunk

r16357: added comments for infix parser tests

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