12-22-2005, 03:31 AM
Under pressure from bluekeyboard, I coded a small formula parser which breaks down and solves a formula (ex (10 ^(2*2))/20+( 90*4)*10+ (1+9)*88 +244 /866- 46^ 2-1 )
Code:
function ParseEq(byval eq as string) as double
dim as integer curLow=4,curInd,numOfOps=0,numOfPar=1
'filter spaces
for c = 0 to len(eq)-1
if eq[c]=32 then eq=left$(eq,c)+right$(eq,len(eq)-c-1)
next c
'get rid of parantheses if they include the whole equation 'ex (234+434*(23+1)) -> 234+434*(23+1)
if eq[0]=40 and eq[len(eq)-1]=41 then
for c = 1 to len(eq)-1
if eq[c]=41 or eq[c]=40 then numOfPar+=(40-eq[c])*2+1
if numOfPar=0 and c<>len(eq)-1 then exit for
if numOfPar=0 and c=len(eq)-1 then eq=mid$(eq,2,len(eq)-2)
next
end if
'find the lowest operator
for c = 0 to len(eq)-1
'skip stuff inside parantheses in the operation count
if eq[c]=40 then '(
numOfPar=1
for tempc = c+1 to len(eq)-1
if eq[tempc]=41 or eq[tempc]=40 then numOfPar+=(40-eq[tempc])*2+1
c=tempc+1
if numOfPar=0 then exit for
next
if c=len(eq) then exit for 'equation end has been reached
end if
if eq[c]=43 or eq[c]=45 or eq[c]=42 or eq[c]=47 or eq[c]=94 then numOfOps+=1
if eq[c]=43 or eq[c]=45 then '+,-
curLow=44-eq[c]
curInd=c
elseif eq[c]=42 or eq[c]=47 then '*,/
if abs(curLow) > 1 then
curLow=-((eq[c]-42)/5*4-2)
curInd=c
end if
elseif eq[c]=94 then '^
if abs(curLow) > 2 then
curLow=3
curInd=c
end if
end if
next
if numOfOps=0 then return val(eq)'single number, no equation to evaluate!
if abs(curLow)= 1 then return ParseEq(left$(eq,curInd)) + ParseEq(right$(eq,len(eq)-curInd-1))*curLow 'split formula into two formulas, the split being at the lowest operation
if curLow= 2 then return ParseEq(left$(eq,curInd)) * ParseEq(right$(eq,len(eq)-curInd-1))
if curLow=-2 then return ParseEq(left$(eq,curInd)) / ParseEq(right$(eq,len(eq)-curInd-1))
if curLow= 3 then return ParseEq(left$(eq,curInd)) ^ ParseEq(right$(eq,len(eq)-curInd-1))
end function
dim as string eq
eq="(10 ^(2*2))/20+( 90*4)*10+ (1+9)*88 +244 /866- 46^ 2-1"
print (10 ^(2*2))/20+( 90*4)*10+ (1+9)*88 +244 /866- 46^ 2-1
print ParseEq(eq)
sleep
