by E P (1 Submission)
Category: Math/Dates
Compatability: Visual Basic 3.0
Difficulty: Intermediate
Date Added: Wed 3rd February 2021
Rating: 
(2 Votes)
This is a QuickBasic program, but I thought it might be useful in your VB projects. It calculates any given numeric equation.
Inputs
In DOS, it will ask you to give any numeric equation containing parentheses, power, multiplication, division, addition, subtraction, and/or negation. Check the screen shot to see an example.
You can add it in your VB project, and just pass the equation to the program.
Code Returns
In DOS, it will print out each step of solving your equation according to the priority of the operations (check out the screen shot).
If you add it in your VB project, you can change it so that it returns an array of the steps or a final answer only.
Side Effects
Like any other program, it has limits as a calculator. Do not try to have a number with an exponent. Do not use 3(4-5), instead, use 3*(4-5).
VBcodersCLS
ON ERROR GOTO ending
t1$ = "Equation Calculator 2.3.5"
t2$ = "By ePuter"
LOCATE 1, 40 - LEN(t1$) / 2: PRINT t1$
LOCATE 2, 40 - LEN(t2$) / 2: PRINT t2$
PRINT
PRINT " Welcome! The program allows you"
PRINT "to enter any equation containing"
PRINT "a parentheses ( or ), power as ^"
PRINT "*, /, +, -, ., and/or a negation"
PRINT "and will give you a step-by-step"
PRINT "solution according to the prior-"
PRINT "ity of the operations."
PRINT " The program will not understand"
PRINT "spaces or any other characters."
PRINT "Enjoy it!"
PRINT : PRINT "Example: 120*-(6+2/(4/2)^3)+60*(54-5)^(1/2)"
PRINT : PRINT
INPUT "Enter the equation: ", maineqzn$
PRINT
PRINT maineqzn$
power = 0
multiply = 1
divide = 2
add = 3
subtract = 4
DO
p = 1
DO
c1 = INSTR(p, maineqzn$, "(")
IF c1 = 0 THEN eqzn$ = maineqzn$: EXIT DO
c2 = INSTR(c1 + 1, maineqzn$, "(")
c3 = INSTR(maineqzn$, ")")
IF c3 < c2 OR c2 = 0 THEN eqzn$ = MID$(maineqzn$, c1 + 1, c3 - c1 - 1): EXIT DO ELSE p = c1 + 1
LOOP
DO
IF INSTR(eqzn$, "E") <> 0 THEN EXIT DO
a = INSTR(eqzn$, "^"): opr = power
IF a = 0 THEN a = INSTR(eqzn$, "*"): opr = multiply
IF a = 0 THEN a = INSTR(eqzn$, "/"): opr = divide
IF a = 0 THEN a = INSTR(eqzn$, "+"): opr = add
IF a = 0 THEN a = INSTR(eqzn$, "-"): opr = subtract
IF a = 1 THEN
a = INSTR(a + 1, eqzn$, "-"): IF a = 0 THEN EXIT DO
END IF
IF a = 0 THEN EXIT DO
i1 = a - 1
DO
repeat1:
i1 = i1 - 1
IF i1 <= 0 THEN i1 = 0: GOTO found1
b$ = MID$(eqzn$, i1, 1)
SELECT CASE VAL(b$)
CASE 1 TO 9: GOTO repeat1
CASE 0:
SELECT CASE b$
CASE ".": GOTO repeat1
CASE "0": GOTO repeat1
CASE "-": i1 = i1 - 1: GOTO found1
CASE ELSE: GOTO found1
END SELECT
END SELECT
LOOP
found1:
i1 = i1 + 1
num1 = VAL(MID$(eqzn$, i1, a - i1))
i2 = a + 1
DO
repeat2:
i2 = i2 + 1
IF i2 >= LEN(eqzn$) THEN i2 = LEN(eqzn$) + 1: GOTO found2
b$ = MID$(eqzn$, i2, 1)
SELECT CASE VAL(b$)
CASE 1 TO 9: GOTO repeat2
CASE 0:
SELECT CASE b$
CASE ".": GOTO repeat2
CASE "0": GOTO repeat2
CASE ELSE: GOTO found2
END SELECT
END SELECT
LOOP
found2:
i2 = i2 - 1
num2 = VAL(MID$(eqzn$, a + 1, i2 - a))
SELECT CASE opr
CASE power: num = num1 ^ num2
CASE multiply: num = num1 * num2
CASE divide:
IF num2 = 0 THEN PRINT : PRINT "Warning: Division by zero.": END ELSE num = num1 / num2
CASE add: num = num1 + num2
CASE subtract: num = num1 - num2
END SELECT
IF num >= 0 THEN
num$ = MID$(STR$(num), 2)
ELSE
num$ = STR$(num)
END IF
IF num1 < 0 THEN
IF num >= 0 AND i1 > 1 THEN num$ = "+" + num$
END IF
eqzn$ = LEFT$(eqzn$, i1 - 1) + num$ + RIGHT$(eqzn$, LEN(eqzn$) - i2)
IF c1 = 0 THEN
PRINT eqzn$
ELSE
PRINT LEFT$(maineqzn$, c1) + eqzn$ + RIGHT$(maineqzn$, LEN(maineqzn$) - c3 + 1)
END IF
IF num < 0 THEN
IF eqzn$ = STR$(num) THEN EXIT DO
ELSE
IF eqzn$ = MID$(STR$(num), 2) THEN EXIT DO
END IF
LOOP
IF c1 <> 0 THEN
maineqzn$ = LEFT$(maineqzn$, c1 - 1) + eqzn$ + RIGHT$(maineqzn$, LEN(maineqzn$) - c3)
PRINT maineqzn$
END IF
LOOP UNTIL c1 = 0
END
ending:
PRINT : PRINT "Warning: Syntax error or overflow.": END
