Algebra in QB

[oracle]

Damn your rawhide Hex!!! :evil: You took my limelight!! I was gonna draw it out on relsoft!!

Oh, and by the way, the curvy x I think is only possible if you copy and paste from MS Word (small letter chi in greek symbols). There may be a code, Hex here is your chance to shine again! (ps 03c7, Alt-X doesn't work here)

[Hexadecimal Disaster]

Rel, no time for today nor tomorrow. Maybe this monday. (just be sure to pop up between 13:00 and 15:00 hrs. of your local time) :roll:

[Agamemnus]

Hey hey, back to the subject: for part of a project I needed to make an arithmetic evaluator. It doesn't do any variable solving though. It just evaluates the expression. (now I have to make this into LISP. But I can't think in LISP, so I didn't.)

(edit: all fixed.)

Code:

DECLARE FUNCTION reduce.string$ (string1$)
CLS
INPUT "Enter expression: ", string1$
IF string1$ = "" THEN string1$ = "(6 * 7) + (8 * 9)"
PRINT string1$ + " = ";
PRINT
string1$ = "(" + string1$ + ")"
DO
string1$ = reduce.string$(string1$)
IF INSTR(string1$, "(") = 0 THEN EXIT DO
LOOP
SLEEP
SYSTEM

FUNCTION reduce.string$ (string1$)
DO
IF string1$ = "" THEN EXIT DO
start.p% = INSTR(string1$, "(")
end.p% = INSTR(string1$, ")")
IF start.p% = 0 THEN EXIT DO
string2$ = string2$ + MID$(string1$, 1, start.p%)
string1$ = MID$(string1$, start.p% + 1, LEN(string1$) - start.p%)
LOOP UNTIL INKEY$ <> ""
end.s1% = INSTR(string1$, ")") - 1
string2$ = MID$(string2$, 1, LEN(string2$) - 1)
string3$ = MID$(string1$, end.s1% + 2, LEN(string1$) - end.s1%)
string1$ = MID$(string1$, 1, end.s1%)

'first find all * and /
DO
dm.exists% = 0
DO
div.exists% = INSTR(string1$, "/ ")
mult.exists% = INSTR(string1$, "* ")
IF div.exists% + mult.exists% <> 0 THEN
IF div.exists% > mult.exists% THEN op$ = "/": op.exists% = div.exists% ELSE op$ = "*": op.exists% = mult.exists%
GOSUB replace.string
dm.exists% = 1
ELSE
EXIT DO
END IF
LOOP UNTIL INKEY$ <> ""
LOOP UNTIL dm.exists% = 0
'then find all + and -
DO
dm.exists% = 0
DO
sub.exists% = INSTR(string1$, "- ")
add.exists% = INSTR(string1$, "+ ")
IF sub.exists% + add.exists% <> 0 THEN
IF sub.exists% > add.exists% THEN op$ = "-": op.exists% = sub.exists% ELSE op$ = "+": op.exists% = add.exists%
GOSUB replace.string
dm.exists% = 1
ELSE
EXIT DO
END IF
LOOP UNTIL INKEY$ <> ""
LOOP UNTIL dm.exists% = 0
reduce.string$ = string2$ + string1$ + string3$
EXIT FUNCTION

replace.string:
num1$ = "": num2$ = ""
i = op.exists% - 2
DO
st$ = MID$(string1$, i, 1)
IF INSTR("0123456789", st$) <> 0 THEN
num2$ = st$ + num2$
ELSE
EXIT DO
END IF
i = i - 1
IF i = 0 THEN i = i + 1: EXIT DO
LOOP
j = i
i = op.exists% + 2
DO
st$ = MID$(string1$, i, 1)
IF INSTR("0123456789", st$) <> 0 THEN
num1$ = num1$ + st$
ELSE
i = i - 1
EXIT DO
END IF
i = i + 1
IF i > LEN(string1$) THEN i = i - 1: EXIT DO
LOOP

SELECT CASE op$
CASE "+": num3$ = LTRIM$(STR$(VAL(num1$) + VAL(num2$)))
CASE "-": num3$ = LTRIM$(STR$(VAL(num2$) - VAL(num1$)))
CASE "*": num3$ = LTRIM$(STR$(VAL(num1$) * VAL(num2$)))
CASE "/": num3$ = LTRIM$(STR$(VAL(num2$) / VAL(num1$)))
END SELECT
string1$ = MID$(string1$, 1, j - 1) + num3$ + MID$(string1$, i + 1, LEN(string1$) - i)
PRINT string2$ + string1$ + string3$
RETURN
END FUNCTION