Perpetual string math calculator.

[SMcNeill]

Since this is string math, I think you guys are overlooking one obvious thing.

Let's take 1/3 for an example -- the answer is "0.33..."

See that "..." at the end there? That tells you that you're dealing with a repeating fraction, Without it, you're just dealing with 0.33. You don't need to go looking for a repeating pattern; just make certain to assign those "..." to the end of your results, and then if you need to reverse engineer the answer, you can easily do so without having to look for a repeating pattern which may or may not be there. "0.33" could be 1/3 rounded to 2 digits, or it could just be 33/100.

Since you're not just doing numeric-math, but are instead doing full fledged string-manipulation, why not give meaningful results with your string answer which holds more information than just numbers can provide?

I'd suggest a simple "...##" approach, where "..." represents something repeating, and "##" represents how many digits before the repetition. With such a method, 1/3 is "0.3...1" -- with one glance you can tell that you have one repeating digit, and it's the 3. From there you can do your reverse magic mumbo jumbo if you need to, to turn it back into 1/3, and then you can process it from there.

1/3 = 0..3...1
0.3...1 * 0.3...1 = (1/3) * (1/3) = (1/9)

[Pete]

No way is Sam going down that rabbit hole. Multiplying fractions works, period. Determining when a repetend is no longer a repetend can get a bit tricky, and even if you made an iron clad system, you will still have accuracy problems with calculations that produce a tremendous amount of digits without repeating. Those can only be accurately used in other calculations when in fraction form.

Pete

[Jack]

I think Steve's idea has merit but it would take some getting used to, it reminds me of continued fractions

[Pete]

The trouble is to use Steve's method requires the algorithm that recognizes a terminating decimal from a repetend. I made one, but since you can have fairly small fractions result in repetends of approx. 10,000 digits before they repeat, you'd waste a lot of computer time running that analysis. It is faster to just calculate both the numerator and denominator and display the results as a decimal. That's the road I took in the code posted in this thread.

Pete

[Pete]

Okay, here is the latest demo update for the various string functions. Please see the first post if you are interested in trying out the string calculator in progress.

Code: (Select All)

DIM SHARED limit&&, betatest%
limit&& = 50: betatest% = -1
REM Demo

PRINT
PRINT "                        1) Turn a fraction into a decimal."
PRINT "                        2) Turn a decimal into a fraction."
PRINT "                        3) Compare string values."
PRINT "                        4) Find the greatest common factor."
PRINT "                        5) Convert to scientific notation."
PRINT "                        6) Convert s.n. to number."
PRINT "                        7) Round to last digit."
PRINT "                        8) Identify decimal repetends."
PRINT "                        9) Convert a repetend to a decimal."
PRINT "                        0) Validate a string number."
PRINT

DO
    _LIMIT 30
    b$ = INKEY$
    IF LEN(b$) THEN
        IF b$ >= "0" AND b$ <= "9" THEN _DELAY .2: EXIT DO
        IF b$ = CHR$(27) THEN SYSTEM
    END IF
LOOP

SELECT CASE b$
    CASE "1"
        LINE INPUT "Numerator:   "; num1$
        LINE INPUT "Denominator: "; num2$
        fraction_to_decimal num1$, num2$, limit&&
    CASE "2"
        LINE INPUT "Decimal:   "; num1$
        decimal_to_fraction num1$, numerator$, denominator$
    CASE "3"
        LINE INPUT "String Number 1: "; num1$
        LINE INPUT "String Number 2: "; num2$
        string_compare num1$, num2$
    CASE "4"
        LINE INPUT "Numerator:   "; num1$
        LINE INPUT "Denominator: "; num2$
        greatest_common_factor num1$, num2$, limit&&
    CASE "5"
        LINE INPUT "Number to convert to s.n: "; num1$
        number_to_scientific num1$
    CASE "6"
        LINE INPUT "S.N. to convert to numeric: "; num1$
        scientific_to_number num1$
    CASE "7"
        LINE INPUT "Number to round: "; num1$
        hold_limit&& = limit&&
        limit&& = LEN(num1$) - 1
        IF INSTR(num1$, ".") THEN limit&& = limit&& - 1
        rounding num1$, limit&&
        limit&& = hold_limit&&
    CASE "8"
        LINE INPUT "Numerator:   "; num1$
        LINE INPUT "Denominator: "; num2$
        operator$ = "/"
        string_math num1$, operator$, num2$, decimal$, limit&&
        repetend_id decimal$, repetend$, repetend_pattern$, repetend_class$, display_as$, z$, mp%
    CASE "9"
        LINE INPUT "Input a repetend: "; num1$
        repetend_to_decimal num1$

    CASE "0"
        LINE INPUT "Number to validate: "; num1$
        validate_string num1$
END SELECT

SLEEP
CLS
RUN

SUB fraction_to_decimal (num1$, num2$, limit&&)
    CALL string_math(num1$, "/", num2$, decimal$, limit&&)
    IF betatest% THEN PRINT "Decimal = "; decimal$
END SUB

SUB decimal_to_fraction (decimal$, numerator$, denominator$)
    IF MID$(decimal$, 1, 1) = "-" THEN j = 3 ELSE j = 2 ' Look for negative sign.
    x1$ = MID$(decimal$, 1, INSTR(decimal$, ".") - 1)
    IF j = 3 THEN x1$ = MID$(x1$, 2)
    x2$ = MID$(decimal$, INSTR(decimal$, ".") + 1)
    denominator$ = "1" + STRING$(LEN(x2$), "0")
    x1$ = x1$ + x2$
    DO UNTIL LEFT$(x1$, 1) <> "0"
        x1$ = MID$(x1$, 2) ' Strip off any leading zeros
    LOOP
    IF j = 2 THEN numerator$ = x1$ ELSE numerator$ = "-" + x1$
    greatest_common_factor numerator$, denominator$, limit&&
END SUB

SUB string_compare (compa$, compb$)
    DO
        REM Remove trailing zeros after a decimal point.
        IF INSTR(compa$, ".") THEN
            DO UNTIL RIGHT$(compa$, 1) <> "0" AND RIGHT$(compa$, 1) <> "." AND RIGHT$(compa$, 1) <> "-"
                compa$ = MID$(compa$, 1, LEN(compa$) - 1)
            LOOP
        END IF
        IF INSTR(compb$, ".") THEN
            DO UNTIL RIGHT$(compb$, 1) <> "0" AND RIGHT$(compb$, 1) <> "." AND RIGHT$(compb$, 1) <> "-"
                compb$ = MID$(compb$, 1, LEN(compb$) - 1)
            LOOP
        END IF

        IF MID$(compa$, 1, 2) = "-0" OR compa$ = "" OR compa$ = "-" THEN compa$ = "0"
        IF MID$(compb$, 1, 2) = "-0" OR compb$ = "" OR compb$ = "-" THEN compb$ = "0"

        ' A - and +
        IF LEFT$(compa$, 1) = "-" THEN j% = -1
        IF LEFT$(compb$, 1) = "-" THEN k% = -1
        IF k% = 0 AND j% THEN gl% = -1: EXIT DO
        IF j% = 0 AND k% THEN gl% = 1: EXIT DO

        ' A decimal and non-decimal.
        j% = INSTR(compa$, ".")
        k% = INSTR(compb$, ".")
        IF j% = 0 AND k% THEN
            IF compa$ = "0" THEN gl% = -1 ELSE gl% = 1
            EXIT DO
        END IF
        IF k% = 0 AND j% THEN
            IF compb$ = "0" THEN gl% = 1 ELSE gl% = -1
            EXIT DO
        END IF

        ' Both decimals.
        IF j% THEN
            IF compa$ > compb$ THEN
                gl% = 1
            ELSEIF compa$ = compb$ THEN gl% = 0
            ELSEIF compa$ < compb$ THEN gl% = -1
            END IF
            EXIT DO
        END IF

        ' Both positive or both negative whole numbers.
        SELECT CASE LEN(compa$)
            CASE IS < LEN(compb$)
                gl% = -1
            CASE IS = LEN(compb$)
                IF compa$ = compb$ THEN
                    gl% = 0
                ELSEIF compa$ > compb$ THEN gl% = 1
                ELSEIF compa$ < compb$ THEN gl% = -1
                END IF
            CASE IS > LEN(compb$)
                gl% = 1
        END SELECT
        EXIT DO
    LOOP

    IF betatest% THEN
        PRINT
        SELECT CASE gl%
            CASE -1
                PRINT "a$ < b$", compa$; " < "; compb$; " gl% = "; gl%
            CASE 0
                PRINT "a$ = b$", compa$; " = "; compb$; " gl% = "; gl%
            CASE 1
                PRINT "a$ > b$", compa$; " > "; compb$; " gl% = "; gl%
        END SELECT
        PRINT
    END IF
END SUB

SUB greatest_common_factor (gfca$, gfcb$, limit&&)
    IF betatest% THEN PRINT "Pre-GFC "; gfca$; " / "; gfcb$
    numerator$ = gfca$: denominator$ = gfcb$
    ' Make both numbers positive.
    IF MID$(gfca$, 1, 1) = "-" THEN gfca$ = MID$(gfca$, 2)
    IF MID$(gfcb$, 1, 1) = "-" THEN gfcb$ = MID$(gfcb$, 2)

    IF gfca$ < gfcb$ THEN SWAP gfca$, gfcb$

    DO
        stringmatha$ = gfca$: stringmathb$ = gfcb$
        operator$ = "/": CALL string_math(stringmatha$, operator$, stringmathb$, runningtotal$, limit&&)
        IF INSTR(runningtotal$, ".") THEN runningtotal$ = MID$(runningtotal$, 1, INSTR(runningtotal$, ".") - 1)
        stringmatha$ = runningtotal$: stringmathb$ = gfcb$
        operator$ = "*": CALL string_math(stringmatha$, operator$, stringmathb$, runningtotal$, limit&&)
        stringmatha$ = gfca$: stringmathb$ = runningtotal$
        operator$ = "-": CALL string_math(stringmatha$, operator$, stringmathb$, runningtotal$, limit&&)
        SWAP gfca$, gfcb$: gfcb$ = runningtotal$
        IF runningtotal$ = "0" THEN EXIT DO
    LOOP

    stringmatha$ = numerator$: stringmathb$ = gfca$
    IF betatest% THEN PRINT "GFC = "; gfca$
    operator$ = "/": CALL string_math(stringmatha$, operator$, stringmathb$, runningtotal$, limit&&)
    numerator$ = runningtotal$
    stringmatha$ = denominator$: stringmathb$ = gfca$
    operator$ = "/": CALL string_math(stringmatha$, operator$, stringmathb$, runningtotal$, limit&&)
    denominator$ = runningtotal$
    IF betatest% THEN PRINT "Fraction: "; numerator$; " / "; denominator$
END SUB

SUB number_to_scientific (stringmathb$)
    IF LEFT$(stringmathb$, 1) = "-" THEN stringmathb$ = MID$(stringmathb$, 2): n2sign$ = "-"
    IF INSTR(stringmathb$, ".") = 0 THEN exponentvalue&& = LEN(stringmathb$) - 1 ELSE exponentvalue&& = INSTR(stringmathb$, ".") - 2 ' Exponent is one less than number of digits for whole number an two less than the placement of the decimal point for a fraction.
    stringmathb$ = MID$(stringmathb$, 1, INSTR(stringmathb$, ".") - 1) + MID$(stringmathb$, INSTR(stringmathb$, ".") + 1)
    IF LEFT$(stringmathb$, 1) = "0" AND LEN(stringmathb$) > 1 OR exponentvalue&& = -1 THEN
        DO UNTIL LEFT$(stringmathb$, 1) <> "0" ' Remove leading zeros to consider rounding.
            stringmathb$ = MID$(stringmathb$, 2)
            exponentvalue&& = exponentvalue&& - 1
        LOOP
        esign$ = "-"
    ELSE
        esign$ = "+"
    END IF
    DO UNTIL RIGHT$(stringmathb$, 1) <> "0" ' Remove trailing zeros.
        stringmathb$ = MID$(stringmathb$, 1, LEN(stringmathb$) - 1)
    LOOP
    IF stringmathb$ = "" THEN stringmathb$ = "0": esign$ = "+": exponentvalue&& = 0
    stringmathb$ = LEFT$(stringmathb$, 1) + "." + MID$(stringmathb$, 2)
    IF stringmathb$ = "0." THEN n2sign$ = "": esign$ = "+"
    stringmathb$ = stringmathb$ + "e" + esign$ + LTRIM$(STR$(ABS(exponentvalue&&))) ' S.N formed here.
    IF stringmathb$ <> "overflow" THEN
        stringmathb$ = n2sign$ + stringmathb$
    END IF
    n2sign$ = "": esign$ = "": exponentvalue&& = 0
    IF betatest% THEN PRINT "S.N.:   "; stringmathb$
END SUB

SUB scientific_to_number (stringmathb$)
    stn_sign$ = "": stn_point$ = ""
    IF INSTR(UCASE$(stringmathb$), "D") THEN MID$(stringmathb$, INSTR(UCASE$(stringmathb$), "D"), 1) = "e"
    IF MID$(stringmathb$, INSTR(stringmathb$, "e") + 2) = "0" THEN ' The numeric value is the number without the zero exponent.
        stringmathb$ = MID$(stringmathb$, 1, INSTR(stringmathb$, "e") - 1)
        IF RIGHT$(stringmathb$, 1) = "." THEN stringmathb$ = MID$(stringmathb$, 1, LEN(stringmathb$) - 1)
        EXIT SUB
    ELSE
        IF LEFT$(stringmathb$, 1) = "-" THEN stn_sign$ = "-": stringmathb$ = MID$(stringmathb$, 2)
        stringmathb$ = MID$(stringmathb$, 1, INSTR(stringmathb$, ".") - 1) + MID$(stringmathb$, INSTR(stringmathb$, ".") + 1) ' Remove decimal point.
        stn_i& = INSTR(stringmathb$, "e") - 1 ' Length of the numric part.
        IF MID$(stringmathb$, INSTR(stringmathb$, "e") + 1, 1) = "-" THEN
            stringmathb$ = "." + STRING$(VAL(MID$(stringmathb$, stn_i& + 3)) - 1, "0") + MID$(stringmathb$, 1, stn_i&) ' Decimal point followed by exponent value in zeros added in front of numeric part.
        ELSE
            IF stn_i& - 1 > VAL(MID$(stringmathb$, stn_i& + 3)) THEN stn_point$ = "." ' - 1 for decimal place. Ex 2.034d+2 is 2034 here where 3 places to the right . could be moved before . disappears. > so no trailing decimal results.
            stringmathb$ = MID$(MID$(stringmathb$, 1, stn_i&), 1, VAL(MID$(stringmathb$, stn_i& + 3)) + 1) + stn_point$ + MID$(MID$(stringmathb$, 1, stn_i&), VAL(MID$(stringmathb$, stn_i& + 3)) + 2, stn_i& - VAL(MID$(stringmathb$, stn_i& + 3)) - 1) + STRING$(VAL(MID$(stringmathb$, stn_i& + 2)) - (stn_i& - 1), "0")
        END IF
    END IF
    IF stringmathb$ = "0" THEN stn_sign$ = ""
    stringmathb$ = stn_sign$ + stringmathb$
    IF betatest% THEN PRINT "Number: "; stringmathb$
END SUB

SUB rounding (stringmathb$, limit&&)
    IF LEN(stringmathb$) > limit&& AND INSTR(stringmathb$, ".") = 0 OR LEN(stringmathb$) > limit&& + 1 AND INSTR(stringmathb$, ".") <> 0 THEN
        IF INSTR(stringmathb$, ".") = 0 THEN
            stringmathb$ = MID$(stringmathb$, 1, limit&& + 1)
        ELSE
            stringmathb$ = MID$(stringmathb$, 1, limit&& + 2)
        END IF

        GOSUB string_rounding_method

        IF LEN(stringmathb$) > limit&& + lrc_decimalpoint& THEN ' Ex: limit&& = 4 9999.9 1.e+4
            CALL number_to_scientific(stringmathb$)
        ELSE
            IF LEN(stringmathb$) > limit&& + lrc_decimalpoint& THEN stringmathb$ = "overflow"
        END IF
    END IF
    IF betatest% THEN PRINT "Rounded: "; stringmathb$
    EXIT SUB

    string_rounding_method:
    IF INSTR(stringmathb$, ".") THEN lrc_decimalpoint& = 1 ELSE lrc_decimalpoint& = 0
    IF MID$(stringmathb$, LEN(stringmathb$), 1) > "4" THEN
        FOR round_i& = LEN(stringmathb$) - 1 TO 1 STEP -1
            round_x$ = CHR$(ASC(MID$(stringmathb$, round_i&, 1)) + 1)
            IF round_x$ <> CHR$(47) THEN ' Decimal point + 1. Ignore.
                IF round_x$ = CHR$(58) THEN
                    MID$(stringmathb$, round_i&, 1) = "0": carry$ = "1"
                ELSE
                    MID$(stringmathb$, round_i&, 1) = round_x$: carry$ = "": EXIT FOR
                END IF
            END IF
        NEXT
        stringmathb$ = carry$ + MID$(stringmathb$, 1, LEN(stringmathb$) - 1): carry$ = ""
        IF show_rounding% THEN stringmathround$ = "R"
    ELSE
        stringmathb$ = MID$(stringmathb$, 1, LEN(stringmathb$) - 1)
        IF show_rounding% THEN stringmathround$ = "r"
    END IF

    IF lrc_decimalpoint& THEN
        DO UNTIL RIGHT$(stringmathb$, 1) <> "0"
            stringmathb$ = MID$(stringmathb$, 1, LEN(stringmathb$) - 1)
        LOOP
        IF stringmathb$ = "" OR stringmathb$ = "." THEN stringmathb$ = "0": lrc_decimalpoint& = 0
        IF RIGHT$(stringmathb$, 1) = "." AND exponentvalue&& = 0 THEN
            stringmathb$ = MID$(stringmathb$, 1, LEN(stringmathb$) - 1): lrc_decimalpoint& = 0
        END IF
    END IF
    RETURN
END SUB

SUB repetend_id (decimal$, repetend$, repetend_pattern$, repetend_class$, display_as$, z$, mp%)
    x$ = MID$(decimal$, INSTR(decimal$, ".") + 1)
    i = 1: j = 0: k = 0: repetend_class$ = ""
    DO
        j = j + 1: k = k + 1
        z$ = MID$(x$, i, j)
        mp% = INSTR(LEN(z$) + i, x$, z$)
        IF betatest% < -1 THEN COLOR 2, 0: PRINT z$, "i ="; i; "Len ="; LEN(z$); "Prog ="; i + LEN(z$); "mp% ="; mp%; "case ="; p: COLOR 7, 0 '': SLEEP
        IF VAL(z$) AND mp% = LEN(z$) + i THEN
            FOR k = 0 TO LEN(MID$(x$, i)) / LEN(z$) - 1
                IF MID$(x$, i + k * LEN(z$), LEN(z$)) <> z$ THEN mp% = -1: EXIT FOR
            NEXT

            IF mp% > 0 THEN
                SELECT CASE LEN(z$)
                    CASE 1
                        IF i = 1 THEN
                            repetend_pattern$ = "Repetend infinite."
                            repetend$ = STRING$(3, z$)
                            repetend_class$ = "single"
                            display_as$ = MID$(decimal$, 1, LEN(z$) + j + INSTR(decimal$, ".") - j) + "..."
                        ELSE
                            repetend_pattern$ = "Repetend eventually infinite."
                            repetend$ = STRING$(3, z$)
                            repetend_class$ = "single"
                            IF LEFT$(decimal$, 1) = "-" THEN j = 2 ELSE j = 1
                            display_as$ = MID$(decimal$, 1, mp% - 1 + j + INSTR(decimal$, ".") - j - 1) + "(" + STRING$(1, z$) + ")"
                        END IF
                    CASE ELSE
                        repetend_pattern$ = "Repetend length = " + LTRIM$(STR$(LEN(z$)))
                        repetend$ = z$
                        repetend_class$ = "mixed"
                        IF LEFT$(decimal$, 1) = "-" THEN j = 2 ELSE j = 1
                        display_as$ = MID$(decimal$, 1, LEN(z$) + j + INSTR(decimal$, ".") - j) + "..."
                END SELECT
                EXIT DO
            END IF
        END IF
        IF LEN(z$) >= (LEN(x$) - i + 1) / 2 THEN
            repetend_pattern$ = "Non-repetend."
            repetend_class$ = "null"
            repetend$ = ""
            display_as$ = decimal$
            EXIT DO
        END IF
        IF mp% = 0 THEN j = 0: i = i + 1
    LOOP

    IF betatest% THEN
        COLOR 14, 0
        PRINT "Decimal: "; decimal$
        IF LEN(repetend$) THEN PRINT "Repetend: "; repetend$
        PRINT "Repetend class: "; repetend_class$
        PRINT repetend_pattern$
        IF mp% > 0 THEN
            PRINT "Repeats at decimal place:"; mp% - 1
            PRINT "May be displayed as: "; display_as$
        END IF
        PRINT: COLOR 7, 0
    END IF
END SUB

SUB repetend_to_decimal (decimal$)
    CALL repetend_id(decimal$, repetend$, repetend_pattern$, repetend_class$, display_as$, z$, mp%)

    SELECT CASE repetend_class$
        CASE "null" ' Terminating decimal.
            IF MID$(decimal$, 1, 1) = "-" THEN j = 3 ELSE j = 2 ' Look for negative sign.
            x1$ = MID$(decimal$, 1, INSTR(decimal$, ".") - 1)
            IF j = 3 THEN x1$ = MID$(x1$, 2)
            x2$ = MID$(decimal$, INSTR(decimal$, ".") + 1)
            denominator$ = "1" + STRING$(LEN(x2$), "0")
            DO UNTIL LEFT$(x2$, 1) <> "0"
                x2$ = MID$(x2$, 2) ' Strip off any leading zeros
            LOOP
            IF j = 2 THEN numerator$ = x1$ + x2$ ELSE numerator$ = "-" + x1$ + x2$

        CASE "single"
            ' Infinite repeating of a single digit.
            ii% = mp% - 1
            stringmatha$ = "1" + STRING$(mp%, "0"): stringmathb$ = decimal$
            operator$ = "*": CALL string_math(stringmatha$, operator$, stringmathb$, runningtotal$, limit&&)

            j = INSTR(runningtotal$, ".")
            IF j THEN
                m1$ = MID$(runningtotal$, 1, INSTR(runningtotal$, ".") - 1)
            ELSE
                m1$ = runningtotal$
            END IF

            stringmatha$ = "1" + STRING$(mp% - 1, "0"): stringmathb$ = decimal$
            operator$ = "*": CALL string_math(stringmatha$, operator$, stringmathb$, runningtotal$, limit&&)
            m2$ = MID$(runningtotal$, 1, INSTR(runningtotal$, ".") - 1)
            stringmatha$ = m1$: stringmathb$ = m2$
            operator$ = "-": CALL string_math(stringmatha$, operator$, stringmathb$, runningtotal$, limit&&)
            numerator$ = runningtotal$

            stringmatha$ = "1" + STRING$(mp%, "0"): stringmathb$ = "1" + STRING$(mp% - 1, "0")
            operator$ = "-": CALL string_math(stringmatha$, operator$, stringmathb$, runningtotal$, limit&&)
            denominator$ = runningtotal$

        CASE ELSE ' Mixed.
            ' Infinite repeating pattern of two or more digits.
            numerator$ = MID$(z$, 1, mp% - 1)
            DO UNTIL LEFT$(numerator$, 1) <> "0"
                a$ = MID$(numerator$, 2) ' Strip off any leading zeros
            LOOP

            stringmatha$ = "1" + STRING$(mp% - 1, "0")
            stringmathb$ = "1" + STRING$((mp% - 1) - LEN(z$), "0")
            operator$ = "-": CALL string_math(stringmatha$, operator$, stringmathb$, runningtotal$, limit&&)
            denominator$ = runningtotal$
    END SELECT
    z$ = ""
    CALL greatest_common_factor(numerator$, denominator$, limit&&)
END SUB

SUB validate_string (stringmathb$)
    DO ' Faux loop.
        vsn_negcnt& = 0: vsn_poscnt& = 0: vsn_depresent& = 0: decimalcnt& = 0: vsn_numberpresent& = 0: vsn_zerospresent& = 0
        IF LEFT$(stringmathb$, 1) = "-" THEN stringmathb$ = MID$(stringmathb$, 2): sm_sign$ = "-" ELSE sm_sign$ = ""
        IF LEFT$(stringmathb$, 1) = "+" THEN IF sm_sign$ <> "-" THEN stringmathb$ = MID$(stringmathb$, 2) ELSE stringmathb$ = "invalid number": EXIT DO
        IF INSTR(UCASE$(stringmathb$), "D") OR INSTR(UCASE$(stringmathb$), "E") THEN ' Evaluate for Scientific Notation.
            FOR sm_i& = 1 TO LEN(stringmathb$)
                validatenum$ = MID$(UCASE$(stringmathb$), sm_i&, 1)
                SELECT CASE validatenum$
                    CASE "+"
                        IF vsn_depresent& THEN vsn_poscnt& = vsn_poscnt& + 1 ELSE stringmathb$ = "invalid number": EXIT DO
                    CASE "-"
                        IF vsn_depresent& THEN vsn_negcnt& = vsn_negcnt& + 1 ELSE stringmathb$ = "invalid number": EXIT DO
                    CASE "0" TO "9"
                        vsn_numberpresent& = -1
                    CASE "D", "E"
                        vsn_depresent& = vsn_depresent& + 1
                        IF decimalcnt& = 0 AND sm_i& <> 2 OR vsn_depresent& > 1 OR vsn_numberpresent& = 0 OR vsn_negcnt& > 1 OR vsn_poscnt& > 1 OR vsn_negcnt& = 1 AND vsn_poscnt& >= 1 THEN vsn_numberpresent& = 0: EXIT FOR
                        vsn_numberpresent& = 0
                        MID$(stringmathb$, sm_i&, 1) = "e" ' Standardize
                    CASE "."
                        decimalcnt& = decimalcnt& + 1
                        IF sm_i& <> 2 THEN vsn_numberpresent& = 0: EXIT FOR
                    CASE ELSE
                        vsn_numberpresent& = 0: EXIT FOR
                END SELECT
            NEXT
            IF decimalcnt& = 0 THEN stringmathb$ = MID$(stringmathb$, 1, 1) + "." + MID$(stringmathb$, 2) ' Standardize "."
            IF vsn_numberpresent& = 0 OR vsn_negcnt& = 1 AND vsn_poscnt& = 1 OR decimalcnt& > 1 OR INSTR(stringmathb$, ".") <> 2 THEN stringmathb$ = "invalid number": EXIT DO
            vsn_depresent& = INSTR(stringmathb$, "e")
            sm_x$ = MID$(stringmathb$, vsn_depresent& + 1, 1) ' Standardize exponent "+" these two lines.
            IF sm_x$ <> "+" AND sm_x$ <> "-" THEN stringmathb$ = MID$(stringmathb$, 1, vsn_depresent&) + "+" + MID$(stringmathb$, vsn_depresent& + 1)
            IF MID$(stringmathb$, vsn_depresent& + 2, 1) = "0" THEN
                IF MID$(stringmathb$, vsn_depresent& + 3, 1) <> "" THEN stringmathb$ = "invalid number": EXIT DO ' No leading zeros allowed in exponent notation.
            END IF
            jjed& = INSTR(stringmathb$, "e") ' Get position of notation.
            valexpside$ = MID$(stringmathb$, jjed&) ' These two lines break up into number and notation
            stringmathb$ = MID$(stringmathb$, 1, jjed& - 1) ' stringmathb$ is +- single digit whole number, decimal point and decimal number. valexpside$ is notation, sign and exponent.
            DO UNTIL RIGHT$(stringmathb$, 1) <> "0" ' Remove any trailing zeros for number. Example 1.0d3 or 1.0000d3, etc.
                stringmathb$ = MID$(stringmathb$, 1, LEN(stringmathb$) - 1)
            LOOP
            IF VAL(MID$(stringmathb$, 1, INSTR(stringmathb$, ".") - 1)) = 0 THEN
                IF RIGHT$(stringmathb$, 1) = "." THEN
                    stringmathb$ = "0.e+0" ' Handles all types of zero entries.
                ELSE
                    stringmathb$ = "invalid number": EXIT DO
                END IF
                EXIT DO
            END IF
            stringmathb$ = sm_sign$ + stringmathb$ + valexpside$
            EXIT DO
        ELSE
            FOR sm_i& = 1 TO LEN(stringmathb$)
                validatenum$ = MID$(stringmathb$, sm_i&, 1)
                SELECT CASE validatenum$
                    CASE "."
                        decimalcnt& = decimalcnt& + 1
                    CASE "0"
                        vsn_zerospresent& = -1
                    CASE "1" TO "9"
                        vsn_numberpresent& = -1
                    CASE "$"
                    CASE ELSE
                        stringmathb$ = "invalid number": EXIT DO
                END SELECT
            NEXT
            IF decimalcnt& > 1 OR vsn_negcnt& > 1 OR vsn_poscnt& > 1 OR vsn_negcnt& >= 1 AND vsn_poscnt& >= 1 THEN
                stringmathb$ = "invalid number": EXIT DO
            END IF

            REM IF INSTR(stringmathb$, "$") THEN GOSUB currency_validate
            REM IF INSTR(stringmathb$, ",") THEN
            REM    GOSUB comma_validation
            REM IF stringmathb$ = "invalid number" THEN exit do
            REM GOSUB comma_removal
            REM END IF

            IF RIGHT$(stringmathb$, 1) = "." THEN stringmathb$ = MID$(stringmathb$, 1, LEN(stringmathb$) - 1)
            DO UNTIL LEFT$(stringmathb$, 1) <> "0" ' Strip off any leading zeros.
                stringmathb$ = MID$(stringmathb$, 2)
            LOOP
            stringmathb$ = sm_sign$ + stringmathb$
            IF INSTR(stringmathb$, ".") THEN
                DO UNTIL RIGHT$(stringmathb$, 1) <> "0" ' Strip off any trailing zeros in a decimal.
                    stringmathb$ = MID$(stringmathb$, 1, LEN(stringmathb$) - 1)
                LOOP
            END IF
            IF RIGHT$(stringmathb$, 1) = "." THEN stringmathb$ = MID$(stringmathb$, 1, LEN(stringmathb$) - 1)
            IF vsn_numberpresent& = 0 THEN
                IF vsn_zerospresent& THEN
                    stringmathb$ = "0"
                ELSE
                    stringmathb$ = "invalid number"
                END IF
            END IF
        END IF
        EXIT DO
    LOOP
    IF betatest% THEN
        IF stringmathb$ = "invalid number" THEN
            PRINT: PRINT "Invalid number."
        ELSE
            PRINT: PRINT "Valid number."
        END IF
    END IF
END SUB

SUB string_math (stringmatha$, operator$, stringmathb$, runningtotal$, limit&&)
    SELECT CASE operator$
        CASE "+", "-"
            GOTO string_add_subtract
        CASE "*"
            GOTO string_multiply
        CASE "/"
            GOTO string_divide
        CASE ELSE
            PRINT "Error, no operator selected. operator$ = "; operator$
    END SELECT

    string_divide:
    divsign% = 0: divremainder& = 0: divremainder$ = "": divplace& = 0: divplace2& = 0: quotient$ = "": divcarry& = 0
    operationdivision% = -1
    divbuffer& = LEN(stringmathb$) - LEN(stringmatha$)
    IF divbuffer& < 0 THEN divbuffer& = 0
    d2dividend$ = stringmatha$
    d1divisor$ = stringmathb$
    IF LEFT$(d1divisor$, 1) = "0" AND LEN(d1divisor$) = 1 THEN PRINT "Division by zero not allowed.": divsign% = 0: operationdivision% = 0: EXIT SUB
    IF LEFT$(d1divisor$, 1) = "-" THEN divsign% = -1: d1divisor$ = MID$(d1divisor$, 2)
    IF LEFT$(d2dividend$, 1) = "-" THEN
        IF divsign% THEN
            divsign% = 0
        ELSE
            divsign% = -1
        END IF
        d2dividend$ = MID$(d2dividend$, 2)
    END IF
    IF INSTR(d1divisor$, ".") <> 0 THEN
        DO UNTIL RIGHT$(d1divisor$, 1) <> "0"
            d1divisor$ = MID$(d1divisor$, 1, LEN(d1divisor$) - 1) ' Strip off trailing zeros
        LOOP
        divplace& = LEN(d1divisor$) - INSTR(d1divisor$, ".")
        d1divisor$ = MID$(d1divisor$, 1, INSTR(d1divisor$, ".") - 1) + MID$(d1divisor$, INSTR(d1divisor$, ".") + 1) ' Strip off decimal point.
        DO UNTIL LEFT$(d1divisor$, 1) <> "0"
            d1divisor$ = MID$(d1divisor$, 2) ' Strip off leading zeros for divisors smaller than .1
        LOOP
    END IF

    IF INSTR(d2dividend$, ".") <> 0 THEN
        d2dividend$ = d2dividend$ + STRING$(divplace& - LEN(d2dividend$) - INSTR(d2dividend$, "."), "0") ' Add any zeros based on the length of dividend at decimal - length of divisor at decimal. If less than zero, nothing added.
        divplace2& = INSTR(d2dividend$, ".")
        DO UNTIL RIGHT$(d2dividend$, 1) <> "0"
            d2dividend$ = MID$(d2dividend$, 1, LEN(d2dividend$) - 1) ' Strip off trailing zeros
        LOOP
        d2dividend$ = MID$(d2dividend$, 1, INSTR(d2dividend$, ".") - 1) + MID$(d2dividend$, INSTR(d2dividend$, ".") + 1) ' Strip off decimal point.
    ELSE
        d2dividend$ = d2dividend$ + STRING$(divplace&, "0") ' Add any zeros based on the length of dividend at decimal - length of divisor at decimal. If less than zero, nothing added.
        divplace& = 0
    END IF
    DO
        DO
            divremainder& = divremainder& + 1: divremainder$ = divremainder$ + MID$(d2dividend$, divremainder&, 1)
            IF MID$(d2dividend$, divremainder&, 1) = "" THEN
                IF divremainder$ = STRING$(LEN(divremainder$), "0") AND LEN(quotient$) > LEN(d2dividend$) THEN divflag% = -1: EXIT DO
                divcarry& = divcarry& + 1
                IF divcarry& = 1 THEN divplace3& = divremainder& - 1
                IF divcarry& > limit&& + 1 + divbuffer& THEN
                    divflag% = -2: EXIT DO
                END IF
                divremainder$ = divremainder$ + "0" ' No more digits to bring down.
            END IF
            IF LEN(divremainder$) > LEN(d1divisor$) OR LEN(divremainder$) = LEN(d1divisor$) AND divremainder$ >= d1divisor$ THEN EXIT DO
            quotient$ = quotient$ + "0"
        LOOP
        IF divflag% THEN divflag% = 0: EXIT DO
        FOR div_i% = 9 TO 1 STEP -1
            stringmatha$ = LTRIM$(STR$(div_i%)): stringmathb$ = d1divisor$
            m_product$ = "": GOSUB string_multiply
            tempcutd$ = divremainder$ ' divremainder$ can be 00 or other leading zero values.
            DO
                IF LEN(tempcutd$) = 1 THEN EXIT DO
                IF LEFT$(tempcutd$, 1) = "0" THEN
                    tempcutd$ = MID$(tempcutd$, 2)
                ELSE
                    EXIT DO
                END IF
            LOOP
            IF LEN(tempcutd$) > LEN(m_product$) OR LEN(tempcutd$) = LEN(m_product$) AND m_product$ <= tempcutd$ THEN EXIT FOR
        NEXT
        quotient$ = quotient$ + LTRIM$(STR$(div_i%))
        stringmatha$ = LTRIM$(STR$(div_i%)): stringmathb$ = d1divisor$
        m_product$ = "": GOSUB string_multiply
        operator$ = "-"
        stringmatha$ = divremainder$
        stringmathb$ = m_product$
        GOSUB string_add_subtract
        divremainder$ = stringmatha$
        operator$ = "/"
    LOOP
    IF divplace& = 0 AND divplace2& = 0 THEN divplace& = divplace3&
    IF divplace2& THEN divplace& = divplace& + divplace2& - 1
    IF quotient$ = "" THEN divplace& = 0 ' dividend is zero.
    IF divplace& OR divplace2& THEN
        quotient$ = MID$(quotient$, 1, divplace&) + "." + MID$(quotient$, divplace& + 1)
        DO UNTIL RIGHT$(quotient$, 1) <> "0"
            quotient$ = MID$(quotient$, 1, LEN(quotient$) - 1) ' Strip off trailing zeros
        LOOP
        IF RIGHT$(quotient$, 1) = "." THEN quotient$ = MID$(quotient$, 1, LEN(quotient$) - 1) ' Strip off abandoned decimal.
    END IF
    DO UNTIL LEFT$(quotient$, 1) <> "0"
        quotient$ = MID$(quotient$, 2) ' Strip off leading zeros
    LOOP
    IF quotient$ = "" THEN quotient$ = "0": divsign% = 0
    operationdivision% = 0
    stringmathb$ = quotient$: quotient$ = ""

    IF stringmathb$ = "overflow" THEN divsign% = 0: operationdivision% = 0: EXIT SUB

    runningtotal$ = stringmathb$: stringmathb$ = ""
    IF divsign% THEN runningtotal$ = "-" + runningtotal$

    IF stringmathround$ <> "" THEN runningtotal$ = runningtotal$ + stringmathround$
    operationdivision% = 0
    EXIT SUB

    string_multiply:
    m_decimal_places& = 0: m_product$ = ""
    fac1$ = stringmatha$: fac2$ = stringmathb$ ' Make numbers whole numbers and remove any - sign.
    IF LEFT$(fac1$, 1) = "-" THEN fac1$ = MID$(fac1$, 2): m_sign% = -1
    IF LEFT$(fac2$, 1) = "-" THEN fac2$ = MID$(fac2$, 2): IF m_sign% THEN m_sign% = 0 ELSE m_sign% = -1
    IF INSTR(fac1$, ".") <> 0 THEN m_decimal_places& = LEN(fac1$) - INSTR(fac1$, "."): fac1$ = MID$(fac1$, 1, INSTR(fac1$, ".") - 1) + MID$(fac1$, INSTR(fac1$, ".") + 1)
    IF INSTR(fac2$, ".") <> 0 THEN m_decimal_places& = m_decimal_places& + LEN(fac2$) - INSTR(fac2$, "."): fac2$ = MID$(fac2$, 1, INSTR(fac2$, ".") - 1) + MID$(fac2$, INSTR(fac2$, ".") + 1)
    FOR m_i& = LEN(fac2$) TO 1 STEP -1 ' Multiply each charater top and bottom.
        m_k& = m_l&
        m_x2$ = MID$(fac2$, m_i&, 1)
        FOR m_j& = LEN(fac1$) TO 1 STEP -1
            m_x1$ = MID$(fac1$, m_j&, 1)
            IF m_product$ <> "" THEN
                m_add$ = LTRIM$(STR$(VAL(m_x1$) * VAL(m_x2$))) + STRING$(m_k&, "0")
                m_t& = 0: m_xproduct$ = "": m_carry% = 0
                DO ' Add multiplied characters together.
                    m_x3$ = MID$(m_add$, LEN(m_add$) - m_t&, 1)
                    m_x4$ = MID$(m_product$, LEN(m_product$) - m_t&, 1)
                    IF m_x3$ = "" AND m_x4$ = "" THEN
                        IF m_carry% THEN m_xproduct$ = "1" + m_xproduct$
                        EXIT DO
                    END IF
                    m_g% = VAL(m_x3$) + VAL(m_x4$) + m_carry%
                    IF m_g% >= 10 THEN m_g% = m_g% - 10: m_carry% = 1 ELSE m_carry% = 0
                    m_xproduct$ = LTRIM$(STR$(m_g%)) + m_xproduct$
                    m_t& = m_t& + 1
                LOOP
                m_product$ = m_xproduct$: m_xproduct$ = ""
            ELSE
                m_product$ = LTRIM$(STR$(VAL(m_x1$) * VAL(m_x2$))) + STRING$(m_k&, "0") ' First loop makes variable here.
            END IF
            m_k& = m_k& + 1 ' Adds trailing zeros multiplication
        NEXT
        m_l& = m_l& + 1 ' Used to reset value for m_k& adding one trailing zer for each loop.
    NEXT
    fac1$ = "": fac2$ = "": m_l& = 0: m_k& = 0: m_t& = 0
    IF m_decimal_places& > LEN(m_product$) THEN m_product$ = STRING$(m_decimal_places& - LEN(m_product$), "0") + m_product$ ' Add any leading zeros to a decimal. Ex: .02 * .01 is factored as 002. It needs one leading zero before adding the decimal point, .0002.
    IF m_decimal_places& AND m_product$ <> "0" THEN ' Replace any decimal point.
        m_product$ = MID$(m_product$, 1, LEN(m_product$) - m_decimal_places&) + "." + MID$(m_product$, LEN(m_product$) - m_decimal_places& + 1)
    END IF
    DO UNTIL LEFT$(m_product$, 1) <> "0" ' Remove leading zeros.
        m_product$ = MID$(m_product$, 2)
    LOOP
    IF m_decimal_places& THEN
        DO UNTIL RIGHT$(m_product$, 1) <> "0" ' Remove trailing zeros in a decimal sum.
            m_product$ = MID$(m_product$, 1, LEN(m_product$) - 1)
        LOOP
    END IF
    IF m_product$ = "" THEN m_product$ = "0": m_sign% = 0
    IF RIGHT$(m_product$, 1) = "." THEN m_product$ = MID$(m_product$, 1, LEN(m_product$) - 1) ' Remove decimal from the end of an integer total.
    IF operationdivision% THEN m_sign% = 0: RETURN
    stringmathb$ = m_product$: m_product$ = ""

    IF stringmathb$ = "overflow" THEN EXIT SUB

    runningtotal$ = stringmathb$: stringmathb$ = ""
    IF m_sign% THEN runningtotal$ = "-" + runningtotal$: m_sign% = 0
    EXIT SUB

    string_add_subtract:
    IF INSTR(stringmatha$, ".") <> 0 THEN ' Evaluate sum for decimal fraction.
        sumplace& = LEN(stringmatha$) - INSTR(stringmatha$, ".")
        stringmatha$ = MID$(stringmatha$, 1, INSTR(stringmatha$, ".") - 1) + MID$(stringmatha$, INSTR(stringmatha$, ".") + 1) ' Strip out decimal
    END IF
    IF INSTR(stringmathb$, ".") <> 0 THEN ' Evaluate number for decimal fraction.
        numplace& = LEN(stringmathb$) - INSTR(stringmathb$, ".")
        stringmathb$ = MID$(stringmathb$, 1, INSTR(stringmathb$, ".") - 1) + MID$(stringmathb$, INSTR(stringmathb$, ".") + 1) ' Strip out decimal
    END IF
    IF sumplace& > numplace& THEN addsubplace& = sumplace& ELSE addsubplace& = numplace&
    IF sumplace& > addsubplace& THEN
        stringmatha$ = stringmatha$ + STRING$(sumplace& - addsubplace&, "0")
    ELSEIF addsubplace& > sumplace& THEN
        stringmatha$ = stringmatha$ + STRING$(addsubplace& - sumplace&, "0")
    END IF
    IF numplace& > addsubplace& THEN
        stringmathb$ = stringmathb$ + STRING$(numplace& - addsubplace&, "0")
    ELSEIF addsubplace& > numplace& THEN
        stringmathb$ = stringmathb$ + STRING$(addsubplace& - numplace&, "0")
    END IF ' END Decimal evaluations.

    IF LEFT$(stringmatha$, 1) = "-" THEN sign_input$ = "-" ELSE sign_input$ = "+"
    IF LEFT$(stringmathb$, 1) = "-" THEN sign_total$ = "-" ELSE sign_total$ = "+"

    addsubsign% = 0
    SELECT CASE sign_input$ + operator$ + sign_total$
        CASE "+++", "+--"
            operator$ = "+"
            IF LEFT$(stringmathb$, 1) = "-" THEN stringmathb$ = MID$(stringmathb$, 2)
        CASE "++-", "+-+"
            operator$ = "-"
            IF LEFT$(stringmathb$, 1) = "-" THEN stringmathb$ = MID$(stringmathb$, 2)
            GOSUB string_comp
            IF gl% < 0 THEN SWAP stringmatha$, stringmathb$: addsubsign% = -1
        CASE "---", "-++"
            operator$ = "-"
            IF LEFT$(stringmatha$, 1) = "-" THEN stringmatha$ = MID$(stringmatha$, 2)
            IF LEFT$(stringmathb$, 1) = "-" THEN stringmathb$ = MID$(stringmathb$, 2)
            GOSUB string_comp
            IF gl% < 0 THEN SWAP stringmatha$, stringmathb$: addsubsign% = -1
        CASE "--+", "-+-"
            operator$ = "+"
            IF LEFT$(stringmatha$, 1) = "-" THEN stringmatha$ = MID$(stringmatha$, 2)
            IF LEFT$(stringmathb$, 1) = "-" THEN stringmathb$ = MID$(stringmathb$, 2)
            addsubsign% = -1
    END SELECT

    IF LEN(stringmatha$) > LEN(stringmathb$) THEN
        stringmathb$ = STRING$(LEN(stringmatha$) - LEN(stringmathb$), "0") + stringmathb$
    ELSEIF LEN(stringmatha$) < LEN(stringmathb$) THEN
        stringmatha$ = STRING$(LEN(stringmathb$) - LEN(stringmatha$), "0") + stringmatha$
    END IF
    addsubx1$ = ""

    SELECT CASE operator$
        CASE "+", "="
            FOR addsubii& = LEN(stringmatha$) TO 1 STEP -1
                addsubx1% = VAL(MID$(stringmatha$, addsubii&, 1)) + VAL(MID$(stringmathb$, addsubii&, 1)) + addsubcarry%
                IF addsubx1% > 9 THEN addsubx1% = addsubx1% - 10: addsubcarry% = 1 ELSE addsubcarry% = 0
                addsubx1$ = LTRIM$(STR$(addsubx1%)) + addsubx1$
            NEXT
            IF addsubcarry% THEN addsubx1$ = "1" + addsubx1$: addsubcarry% = 0
            GOSUB replace_decimal
        CASE "-"
            FOR addsubii& = LEN(stringmatha$) TO 1 STEP -1
                addsubx1% = VAL(MID$(stringmatha$, addsubii&, 1)) - VAL(MID$(stringmathb$, addsubii&, 1)) + addsubcarry%
                IF addsubx1% < 0 THEN addsubx1% = addsubx1% + 10: addsubcarry% = -1 ELSE addsubcarry% = 0
                addsubx1$ = LTRIM$(STR$(addsubx1%)) + addsubx1$
            NEXT
            IF addsubx1$ <> "" AND addsubx1$ <> STRING$(LEN(addsubx1$), "0") THEN GOSUB replace_decimal
            DO UNTIL LEFT$(addsubx1$, 1) <> "0" ' Remove leading zeros.
                addsubx1$ = MID$(addsubx1$, 2)
            LOOP
            IF addsubx1$ = "" THEN
                addsubx1$ = "0": addsubsign% = 0
            ELSE
                IF addsubcarry% THEN addsubx1$ = "-" + addsubx1$: addsubcarry% = 0
            END IF
    END SELECT

    IF addsubsign% THEN
        IF LEFT$(addsubx1$, 1) = "-" THEN addsubx1$ = MID$(addsubx1$, 2) ELSE addsubx1$ = "-" + addsubx1$
    END IF
    stringmatha$ = addsubx1$: addsubx1$ = ""
    IF operationdivision% THEN RETURN
    stringmathb$ = stringmatha$: stringmatha$ = ""
    IF LEFT$(stringmathb$, 1) = "-" THEN
        stringmathb$ = MID$(stringmathb$, 2)
        n2sign$ = "-"
    ELSE
        n2sign$ = ""
    END IF

    IF stringmathb$ = "overflow" THEN n2sign$ = "": EXIT SUB

    runningtotal$ = n2sign$ + stringmathb$: n2sign$ = ""
    EXIT SUB

    replace_decimal:
    IF addsubplace& THEN
        addsubx1$ = STRING$(addsubplace& - LEN(addsubx1$), "0") + addsubx1$
        addsubx1$ = MID$(addsubx1$, 1, LEN(addsubx1$) - addsubplace&) + "." + MID$(addsubx1$, LEN(addsubx1$) - addsubplace& + 1)
        DO UNTIL RIGHT$(addsubx1$, 1) <> "0" ' Remove trailing zeros in a decimal sum.
            addsubx1$ = MID$(addsubx1$, 1, LEN(addsubx1$) - 1)
            addsubplace& = addsubplace& - 1
        LOOP
        IF RIGHT$(addsubx1$, 1) = "." THEN addsubx1$ = MID$(addsubx1$, 1, LEN(addsubx1$) - 1) ' Number is now an integer.
    END IF
    RETURN

    string_comp:
    DO
        REM Remove trailing zeros after a decimal point.
        IF INSTR(acomp$, ".") THEN
            DO UNTIL RIGHT$(acomp$, 1) <> "0" AND RIGHT$(acomp$, 1) <> "." AND RIGHT$(acomp$, 1) <> "-"
                acomp$ = MID$(acomp$, 1, LEN(acomp$) - 1)
            LOOP
        END IF
        IF INSTR(bcomp$, ".") THEN
            DO UNTIL RIGHT$(bcomp$, 1) <> "0" AND RIGHT$(bcomp$, 1) <> "." AND RIGHT$(bcomp$, 1) <> "-"
                bcomp$ = MID$(bcomp$, 1, LEN(bcomp$) - 1)
            LOOP
        END IF

        IF MID$(acomp$, 1, 2) = "-0" OR acomp$ = "" OR acomp$ = "-" THEN acomp$ = "0"
        IF MID$(bcomp$, 1, 2) = "-0" OR bcomp$ = "" OR bcomp$ = "-" THEN bcomp$ = "0"

        ' A - and +
        IF LEFT$(acomp$, 1) = "-" THEN j% = -1
        IF LEFT$(bcomp$, 1) = "-" THEN k% = -1
        IF k% = 0 AND j% THEN gl% = -1: EXIT DO
        IF j% = 0 AND k% THEN gl% = 1: EXIT DO

        ' A decimal and non-decimal.
        j% = INSTR(acomp$, ".")
        k% = INSTR(bcomp$, ".")
        IF j% = 0 AND k% THEN
            IF acomp$ = "0" THEN gl% = -1 ELSE gl% = 1
            EXIT DO
        END IF
        IF k% = 0 AND j% THEN
            IF bcomp$ = "0" THEN gl% = 1 ELSE gl% = -1
            EXIT DO
        END IF

        ' Both decimals.
        IF j% THEN
            IF acomp$ > bcomp$ THEN
                gl% = 1
            ELSEIF acomp$ = bcomp$ THEN gl% = 0
            ELSEIF acomp$ < bcomp$ THEN gl% = -1
            END IF
            EXIT DO
        END IF

        ' Both positive or both negative whole numbers.
        SELECT CASE LEN(acomp$)
            CASE IS < LEN(bcomp$)
                gl% = -1
            CASE IS = LEN(bcomp$)
                IF acomp$ = bcomp$ THEN
                    gl% = 0
                ELSEIF acomp$ > bcomp$ THEN gl% = 1
                ELSEIF acomp$ < bcomp$ THEN gl% = -1
                END IF
            CASE IS > LEN(bcomp$)
                gl% = 1
        END SELECT
        EXIT DO
    LOOP
    RETURN
END SUB

Pete

[Kernelpanic]

Well, none of the local experts noticed that the result in Visual Basic was wrong? 

That is corrext:

Code: (Select All)

Private Sub cmdCommand_Click()

  Dim Zahl1, Zahl2, Ergebnis As Double
 
  'Die Zahlen müssen einzeln aus den Textfeldern gelesen werden
  'Das "Ergebnis = Val(txtZahl1.Text + txtZahl2.Text)" geht nicht
  Zahl1 = Val(txtZahl1.Text)
  Zahl2 = Val(txtZahl2.Text)
  Ergebnis = Zahl1 + Zahl2
  txtErgebnis.Text = Format$(Ergebnis, "###.##") 'Punkt! Englische Version.

End Sub

Give me a gun!