'===========================================================================
' Subject: UNLIMITED DIGIT INTEGERS           Date: 10-27-96 (00:00)       
'  Author: Tom Nelson (Chien-Lung Su)         Code: QB, QBasic, PDS        
'  Origin: cs85107@cc.chpi.edu.tw           Packet: ALGOR.ABC
'===========================================================================
' Program name   : "Unlimited-digit integers addition & multiplication"
' Author         : Tom Nelson (Chien-Lung Su)
' Date           : 1996/10/27
' Copyright      : Feel free to use it in your programs.
'                  Or you can send a copy of your product to me ! :)
' Notice         : No error-checking on the given strings for operations !
'                  i.e. You should develop error-preventing code yourself !
' E-mail address : tomnelson.bbs@tnbbs.tnmgeb.edu.tw
'                  cs85107@cc.chpi.edu.tw
'                  cs85107@cssun1.cs.chpi.edu.tw
' Home page      : http://web.chpi.edu.tw/~cs85107/    \
'                  http://web.cs.chpi.edu.tw/~cs85107/ |-> Coming soon !
'                  http://Lung.dorm.chpi.edu.tw/       /
' P.S.           : This program has Turbo Pascal version. If you would
'                  like to take a view of it, please contact me !

DECLARE FUNCTION UnlimitedMul$ (NumString1$, NumString2$)
' The great function of the program ! :)
DECLARE FUNCTION StrMul$ (NumString1$, NumString2$)
' A function performs a 1-digit integer to multi-digit integer multiplication.
DECLARE FUNCTION StrAdd$ (NumString1$, NumString2$)
' A function performs integer addition.
' Called by the two functions above.

CLS
PRINT "Unlimited-digit integers addition & multiplication."
PRINT "Written By Tom Nelson 1996."
PRINT
INPUT "Enter the 1st number : ", Num1$
INPUT "Enter the 2nd number : ", Num2$
Num1$ = LTRIM$(RTRIM$(Num1$))
Num2$ = LTRIM$(RTRIM$(Num2$))
PRINT

IF LEN(Num1$) > LEN(Num2$) THEN
   Max1% = LEN(Num1$)
ELSE
   Max1% = LEN(Num2$)
END IF

Max2% = LEN(Num1$) + LEN(Num2$) - 1
PRINT SPACE$(Max2% - LEN(Num1$) + 3) + Num1$
PRINT "x) " + SPACE$(Max2% - LEN(Num2$)) + Num2$
PRINT STRING$(Max2% + 3, "-")
PRINT SPACE$(Max2% - LEN(UnlimitedMul$(Num1$, Num2$)) + 3) + UnlimitedMul$(Num1$, Num2$)
PRINT
PRINT SPACE$(Max1% - LEN(Num1$) + 3) + Num1$
PRINT "+) " + SPACE$(Max1% - LEN(Num2$)) + Num2$
PRINT STRING$(Max1% + 3, "-")
PRINT SPACE$(Max1% - LEN(StrAdd$(Num1$, Num2$)) + 3) + StrAdd$(Num1$, Num2$)
END



FUNCTION StrAdd$ (NumString1$, NumString2$)
IF NumString1$ = "" OR NumString2$ = "" THEN EXIT FUNCTION
DIM Array1%(1024)
DIM Array2%(1024)
DIM Array3%(1024)

Add1$ = LTRIM$(RTRIM$(NumString1$))
Add2$ = LTRIM$(RTRIM$(NumString2$))
Len1% = LEN(Add1$)
Len2% = LEN(Add2$)

FOR Temp% = 1 TO Len1%
    Array1%(Temp%) = VAL(MID$(Add1$, Len1% + 1 - Temp%, 1))
NEXT Temp%

FOR Temp% = 1 TO Len2%
    Array2%(Temp%) = VAL(MID$(Add2$, Len2% + 1 - Temp%, 1))
NEXT Temp%

IF Len1% > Len2% THEN Max% = Len1% ELSE Max% = Len2%

FOR Temp% = 1 TO Max% + 1
Sum% = Array1%(Temp%) + Array2%(Temp%) + CarryFlag%
IF Sum% >= 10 THEN
   CarryFlag% = 1
   Array3%(Temp%) = Sum% - 10
ELSE
   CarryFlag% = 0
   Array3%(Temp%) = Sum%
END IF
NEXT Temp%

FOR Temp% = Max% + 1 TO 1 STEP -1
Result$ = Result$ + LTRIM$(STR$(Array3%(Temp%)))
NEXT Temp%

FOR Temp% = 1 TO LEN(Result$)
IF MID$(Result$, Temp%, 1) <> "0" THEN
   Okay$ = MID$(Result$, Temp%, LEN(Result$) + 1 - Temp%)
   EXIT FOR
END IF
NEXT Temp%

ERASE Array1%
ERASE Array2%
ERASE Array3%
StrAdd$ = Okay$
END FUNCTION



FUNCTION StrMul$ (NumString1$, NumString2$)
IF NumString1$ = "" OR NumString2$ = "" THEN EXIT FUNCTION

Len1% = LEN(LTRIM$(RTRIM$(NumString1$)))
Len2% = LEN(LTRIM$(RTRIM$(NumString2$)))

DIM Array1$(1024)

IF Len1% >= 1 AND Len2% = 1 THEN
   Begin% = Len1%
   Mul1$ = LTRIM$(RTRIM$(NumString1$))
   Mul2$ = LTRIM$(RTRIM$(NumString2$))
ELSEIF Len1% = 1 AND Len2% >= 1 THEN
   Begin% = Len2%
   Mul1$ = LTRIM$(RTRIM$(NumString2$))
   Mul2$ = LTRIM$(RTRIM$(NumString1$))
ELSE
   EXIT FUNCTION
END IF

FOR Times% = Begin% TO 1 STEP -1
Temp% = VAL(MID$(Mul1$, Times%, 1)) * VAL(Mul2$)
Array1$(Begin% - Times% + 1) = LTRIM$(STR$(Temp%)) + STRING$(Begin% - Times%, "0")
NEXT Times%

FOR Times% = 2 TO Begin%
Array1$(1) = StrAdd$(Array1$(1), Array1$(Times%))
NEXT Times%
StrMul$ = Array1$(1)
ERASE Array1$
END FUNCTION



FUNCTION UnlimitedMul$ (NumString1$, NumString2$)
Length2% = LEN(LTRIM$(RTRIM$(NumString2$)))
DIM Sum$(Length2%)

FOR I% = Length2% TO 1 STEP -1
Sum$(Length2% - I% + 1) = StrMul$(NumString1$, MID$(NumString2$, I%, 1)) + STRING$(Length2% - I%, "0")
NEXT I%

Temp$ = Sum$(1)
FOR Times% = 2 TO Length2%
Temp$ = StrAdd$(Temp$, Sum$(Times%))
NEXT Times%

UnlimitedMul$ = Temp$
ERASE Sum$
Temp$ = ""
END FUNCTION