This simple math solver doesn't work right!

[LemonWizard]

Can someone help me?
This is probably the most terrible approach I could take.
But it seems to be the most compact so far. out of all the ones i've used/tried that didn't quite work.

PlayBASIC Code: [Select]

; PROJECT : Smart_Parse
; AUTHOR  : LemonWizard
; CREATED : 4/20/2014
; EDITED  : 4/20/2014
; ---------------------------------------------------------------------

BB$="10+20+100-8"

print 10+20+100-8

dim arr$(100)
dim operations$(100)



dim BB$(100)
tkns=splittoarray(BB$, "+"+"-"+"/"+"*", arr$(), 0)
      found=0
   for t=0 to len(BB$)
   if mid$(BB$, t, 1)="+"
      operations$(found)="add"
      found=found+1
   endif
      
      
   if mid$(BB$, t, 1)="-" 
      operations$(found)="sub"
      found=found+1
   endif
      
      
   if mid$(BB$, t, 1)="*" 
      operations$(found)="mult"
      found=found+1
   endif
   
   if mid$(BB$, t, 1)="/" 
      operations$(found)="div"
      found=found+1
   endif
   
      
next t
   

st=0
for a=0 to tkns+found
   
   if operations$(a)="add" 
      
      if a=0
         n=val(arr$(a))+val(arr$(a+1))
         st=st+2
      endif
         
      
      if a>0
         n=n+val(arr$(a))
         st=st+1
      endif
      
   endif
      
      
      if operations$(a)="sub"
         
         if a=0
            n=val(arr$(a))-val(arr$(a+1))
         st=st+2
         endif
            
         if a>0
             n=(n-val(arr$(st)))
            st=st+1
            endif
               
   endif
   

      
      
         if operations$(a)="mult"
            
            if a=0
               n=val(arr$(a))*val(arr$(a+1))
               st=st+2
            endif
               
            if a>0 
               n=n*val(arr$(st))
            st=st+1
            endif
               
         endif
         
         if operations$(a)="div"
            
            if a=0
               n=val(arr$(a))/val(arr$(a+1))
               st=st+2
            endif
               
            if a>0 
               n=(n/val( arr$(st)) )
            st=st+1
            endif
               
         endif
                  
                  //print "step is " +str$(a)
                     //print "value of N is "+str$(n)
                  //print "the value of the last operation was " +str$( val( arr$(st)))
   
   
next a

print "the answer is " +str$( n)
   


waitkey
waitnokey

[kevin]

  

Can someone help me?

   Pretty much everything you need to know is explained in the Simple (tokenised) Math Formula Tutorial..  

   Here's a tweaked version of your code.   Be aware there's no precedence !

PlayBASIC Code: [Select]

   Constant MathOpp_ADD   =1
   Constant MathOpp_SUB   =2

   BB$="10+20+100-8"
   print 10+20+100-8

   dim Numbers(100)
   dim operations(100)


   ; ---------------------------------------------------------------------------   
   ; split the start expression on symbols
   ; ---------------------------------------------------------------------------   
   tkns=splittoarray(BB$, "+-", numbers(), 0)

   NumberOfOperators=0

   ; ---------------------------------------------------------------------------   
   ; search for operators
   ; ---------------------------------------------------------------------------   
   for t=0 to len(BB$)
         ThisCHR=mid(BB$, t)
         if ThisChr=asc("+")
               operations(NumberOfOperators)=MathOpp_ADD
               NumberOfOperators++
         endif
      
         if ThisChr=asc("-")
               operations(NumberOfOperators)=MathOpp_SUB
               NumberOfOperators++
         endif
   next t
   
   
   ; ---------------------------------------------------------------------------   
   ; evaulate expression
   ; ---------------------------------------------------------------------------   

   Result =Numbers(0)
   NumberINdex=1

   For lp=0 to NumberOfOperators-1

         ThisValue=Numbers(NumberIndex)
         Operation      =operations(lp)

         Select Operation
         
                  case MathOpp_ADD   
                        Result +=ThisValue 

                        print "Add "+str$(Thisvalue)
                        NumberIndex++
                        
                  case MathOpp_SUB
                        Result -=ThisValue 
                        print "Sub "+str$(Thisvalue)
                        NumberIndex++

                  default 
                        print " unknown"
         
         endselect
   
            
   next

   print "Result="+Str$(result)

   
   
   sync
   waitkey
   

[LemonWizard]

Thank you :D

[kevin]

 no worries, but where do i send the invoice ?   :P

[LemonWizard]

no worries, but where do i send the invoice ?   :P

you're funny Kevin :O

[LemonWizard]

okay so I tried to tweak the version I was working on based on what I saw you do but no matter what , mine is still throwing messed up results.... can you explain to me what you changed precisely so I can understand where I went wrong? I just wanna know if it's something to do with val or something. you know. Just trying to wrap my head around this. >.<

[kevin]

   it works like this   Simple (tokenised) Math Formula Tutorial.. 

  part 1)   break the input string into numbers via SplitToArray

  part 2)  skims the original string looking for operator characters, if it one exists, it puts it into an operators array (stack).   

  part 3)  grabs the first value form the numbers (our starting value), the proceeds to scan the operators array.  When it finds a known operator (Addition/subtraction) it grabs the next value from the numbers arrays and either adds or subtract it from the result...

   really you should read the tutorial, this is exactly why i wrote it !

 

[LemonWizard]

Thanks I will