08-19-2022, 11:26 AM
I haven't tested it extensively yet, but here's a quick string add and string subtract routine for math:
As I mentioned before, all my subtraction routine is, is just addition with an inverted sign!
18 digit chunks at a time, so it processes fairly quickly as far as string routines go with math.
Note: When dealing with multiplication, you can only handle 9 characters at a time. 100 * 100 = 10,000... You have to add the zeros to determine how large a result you can hold in one chunk.
I tried to comment the processes above fairly well, so hopefully they won't be too hard to understand and follow for anyone who's interested in playing around and learning about using strings to do math.
Code: (Select All)
Screen _NewImage(1280, 720, 32)
'a$ = "-10000000000000000000123.256"
'b$ = " 60000000000000000000000.111"
a$ = " 100000000000000000000000000"
b$ = "-000000000000000000000000001.1"
Print a$
Print b$
Print StringAdd(a$, b$)
Print StringSubtract(a$, b$)
Function StringAdd$ (tempa$, tempb$)
a$ = tempa$: b$ = tempb$ 'don't alter our original numbers
Dim As _Unsigned _Integer64 a, b, c 'to hold our values
'first fix the numbers to notmalize their lengths
FixNumbers a$, b$
'find the signs and strip them off
If Left$(a$, 1) = "-" Then sa$ = "-": a$ = Mid$(a$, 2)
If Left$(b$, 1) = "-" Then sb$ = "-": b$ = Mid$(b$, 2)
'find the decimal position
dp = InStr(a$, ".")
If dp > 0 Then 'remove the decimal place from our numbers. We can put it back later, in its proper position
righta$ = Mid$(a$, dp + 1)
rightb$ = Mid$(b$, dp + 1)
a$ = Left$(a$, dp - 1) + righta$
b$ = Left$(b$, dp - 1) + rightb$
End If
'our strings are now nothing but numbers with no signs and no decimals to deal with. Let's start adding!
'are we adding or really subtracting?
If sa$ <> sb$ Then 'we're subtracting the two values if the signs aren't the same.
Select Case a$
Case Is < b$: s$ = sb$: Swap a$, b$ 'our sign is going to be determiined by b$
Case Is = b$ 'if the two values are the same and are subtracting, our result is zero!
StringAdd$ = "0" 'How easy was that?
Exit Function
Case Else: s$ = sa$ 'our sign is determined by a$
End Select
Do
lb = Len(b$)
a = Val(Right$(a$, 18)): a$ = Left$(a$, Len(a$) - 18)
b = Val(Right$(b$, 18)): b$ = Left$(b$, Len(b$) - 18)
If borrow Then b = b + 1 'in case we had to borrow a digit for the last subtraction
If a < b Then
If lb < 18 Then a = a + 10 ^ lb Else a = a + 10 ^ 18
borrow = -1
Else
borrow = 0
End If
c = a - b
temp$ = _Trim$(Str$(c))
answer$ = String$(18 - Len(temp$), "0") + temp$ + answer$
Loop Until Len(a$) = 0
'remove leading 0's
Do Until Left$(answer$, 1) <> "0"
answer$ = Mid$(answer$, 2)
Loop
'remember to add in the decimal place before finished
dp = Len(righta$)
If dp > 0 Then
answer$ = Left$(answer$, Len(answer$) - dp) + "." + Right$(answer$, dp)
End If
StringAdd$ = s$ + answer$
Exit Function
End If
Do
a = Val(Right$(a$, 18)): a$ = Left$(a$, Len(a$) - 18)
b = Val(Right$(b$, 18)): b$ = Left$(b$, Len(b$) - 18)
c = a + b + carryover
temp$ = _Trim$(Str$(c))
If Len(temp$) > 18 Then 'see if we have an answer that is more than 18 digits
temp$ = Right$(temp$, 18) 'keep 18 digits
carryover = 1 'store one for carry over
Else
carryover = 0 'no carryover
End If
answer$ = String$(18 - Len(temp$), "0") + temp$ + answer$
Loop Until Len(a$) = 0
If carryover Then answer$ = "1" + answer$
'remember to add in the decimal place before finished
If dp > 0 Then
dp = Len(tempa$) - dp
answer$ = Left$(answer$, Len(answer$) - dp) + "." + Right$(answer$, dp)
End If
'remove leading 0's
Do Until Left$(answer$, 1) <> "0"
answer$ = Mid$(answer$, 2)
Loop
StringAdd$ = sa$ + answer$
End Function
Function StringSubtract$ (tempa$, tempb$)
a$ = tempa$: b$ = tempb$
FixNumbers a$, b$
If Left$(b$, 1) = "-" Then b$ = Mid$(b$, 2) Else b$ = "-" + b$
StringSubtract$ = StringAdd$(a$, b$)
End Function
Sub FixNumbers (a$, b$)
'first remove scientific notation and spaces from both
a$ = _Trim$(N2S$(a$)): b$ = _Trim$(N2S$(b$))
'then find the decimal position for both and normalize the expressions
d1 = InStr(a$, "."): d2 = InStr(b$, ".")
If d1 <> 0 Then 'break down the left and right side of the decimal point for ease of processing (this is a$)
lefta$ = Left$(a$, d1 - 1)
righta$ = Mid$(a$, d1)
Else
lefta$ = a$
End If
If d2 <> 0 Then 'break down the left and right side of the decimal point for ease of processing (this is b$)
leftb$ = Left$(b$, d2 - 1)
rightb$ = Mid$(b$, d2)
Else
leftb$ = b$
End If
'normalize the right side of our expressions
l1 = Len(righta$): l2 = Len(rightb$)
If l1 < l2 Then
addzero = l2 - l1
If l1 = 0 Then righta$ = ".": addzero = addzero - 1
righta$ = righta$ + String$(addzero, "0")
ElseIf l1 > l2 Then
addzero = l1 - l2
If l2 = 0 Then rightb$ = ".": addzero = addzero - 1
rightb$ = rightb$ + String$(addzero, "0")
End If
'strip off any plus/minus signs from the two numbers.
If Left$(lefta$, 1) = "-" Then signa$ = "-": lefta$ = Mid$(lefta$, 2)
If Left$(leftb$, 1) = "-" Then signb$ = "-": leftb$ = Mid$(leftb$, 2)
If Left$(lefta$, 1) = "+" Then signa$ = "": lefta$ = Mid$(lefta$, 2)
If Left$(leftb$, 1) = "+" Then signb$ = "": leftb$ = Mid$(leftb$, 2)
'normalize the left side of our expressions
l1 = Len(lefta$): l2 = Len(leftb$)
If l1 < l2 Then
addzero = l2 - l1
lefta$ = String$(addzero, "0") + lefta$
ElseIf l1 > l2 Then
addzero = l1 - l2
leftb$ = String$(addzero, "0") + leftb$
End If
'and then put it all together
a$ = signa$ + lefta$ + righta$
b$ = signb$ + leftb$ + rightb$
End Sub
Function N2S$ (exp$) 'scientific Notation to String
t$ = LTrim$(RTrim$(exp$))
If Left$(t$, 1) = "-" Or Left$(t$, 1) = "N" Then sign$ = "-": t$ = Mid$(t$, 2)
dp = InStr(t$, "D+"): dm = InStr(t$, "D-")
ep = InStr(t$, "E+"): em = InStr(t$, "E-")
check1 = Sgn(dp) + Sgn(dm) + Sgn(ep) + Sgn(em)
If check1 < 1 Or check1 > 1 Then N2S = exp$: Exit Function 'If no scientic notation is found, or if we find more than 1 type, it's not SN!
Select Case l 'l now tells us where the SN starts at.
Case Is < dp: l = dp
Case Is < dm: l = dm
Case Is < ep: l = ep
Case Is < em: l = em
End Select
l$ = Left$(t$, l - 1) 'The left of the SN
r$ = Mid$(t$, l + 1): r&& = Val(r$) 'The right of the SN, turned into a workable long
If InStr(l$, ".") Then 'Location of the decimal, if any
If r&& > 0 Then
r&& = r&& - Len(l$) + 2
Else
r&& = r&& + 1
End If
l$ = Left$(l$, 1) + Mid$(l$, 3)
End If
Select Case r&&
Case 0 'what the heck? We solved it already?
'l$ = l$
Case Is < 0
For i = 1 To -r&&
l$ = "0" + l$
Next
l$ = "0." + l$
Case Else
For i = 1 To r&&
l$ = l$ + "0"
Next
End Select
N2S$ = sign$ + l$
End Function
Function DWD$ (exp$) 'Deal With Duplicates
'To deal with duplicate operators in our code.
'Such as -- becomes a +
'++ becomes a +
'+- becomes a -
'-+ becomes a -
t$ = exp$
Do
bad = 0
Do
l = InStr(t$, "++")
If l Then t$ = Left$(t$, l - 1) + "+" + Mid$(t$, l + 2): bad = -1
Loop Until l = 0
Do
l = InStr(t$, "+-")
If l Then t$ = Left$(t$, l - 1) + "-" + Mid$(t$, l + 2): bad = -1
Loop Until l = 0
Do
l = InStr(t$, "-+")
If l Then t$ = Left$(t$, l - 1) + "-" + Mid$(t$, l + 2): bad = -1
Loop Until l = 0
Do
l = InStr(t$, "--")
If l Then t$ = Left$(t$, l - 1) + "+" + Mid$(t$, l + 2): bad = -1
Loop Until l = 0
Loop Until Not bad
DWD$ = t$
End FunctionAs I mentioned before, all my subtraction routine is, is just addition with an inverted sign!
Code: (Select All)
Function StringSubtract$ (tempa$, tempb$)
a$ = tempa$: b$ = tempb$
FixNumbers a$, b$
If Left$(b$, 1) = "-" Then b$ = Mid$(b$, 2) Else b$ = "-" + b$
StringSubtract$ = StringAdd$(a$, b$)
End Function18 digit chunks at a time, so it processes fairly quickly as far as string routines go with math.
Note: When dealing with multiplication, you can only handle 9 characters at a time. 100 * 100 = 10,000... You have to add the zeros to determine how large a result you can hold in one chunk.
I tried to comment the processes above fairly well, so hopefully they won't be too hard to understand and follow for anyone who's interested in playing around and learning about using strings to do math.