===========================================================================
 BBS: The Abacus * HST/DS * Potterville, MI
Date: 03-19-93 (21:00)             Number: 115
From: QUINN TYLER JACKSON          Refer#: NONE
  To: ALL                           Recvd: NO  
Subj: Formula Solver 1.4    4/       Conf: (35) Quick Basi
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    ' Push the parameters to the variable stack temporarily

    IF SymPtr < SYMMAX THEN
        ' Since it wasn't, put it there
        VariPtr = VariPtr + 1
        SymPtr = SymPtr + 1

        IF VariPtr <= VARMAX THEN
            SymTable(SymPtr).SymName = Param$(i%)
            SymTable(SymPtr).SymType = SymVARIABLE
            SymTable(SymPtr).TabPtr = VariPtr
            SymTable(SymPtr).SymLvl = LvlPtr + 1
            VarTable(VariPtr) = ParValue(i%)
        ELSE
            ErrorCode = eqjVariableTableFull
        END IF
    ELSE
        ErrorCode = eqjSymbolTableFull
    END IF

NEXT i%

fqjSolveFormula = fqjEvaluate(Formula$)

VariPtr = VariPtr - Tot%    ' Clear the variable stack of
SymPtr = SymPtr - Tot%      ' variables used in parameter
END FUNCTION

FUNCTION fqjVAL (InText$)

' Initialize some variables....

IF LvlPtr < MAXLEVELS THEN
    LvlPtr = LvlPtr + 1

    DIM CommandArray$(MAXCOMMANDS)

        ' separate statement by semicolons
        CALL sjfParse(CommandArray$(), InText$, ";", Tot%)

        FOR i% = 1 TO Tot%
            fqjVAL = fqjEval(CommandArray$(i%))

            IF ErrorCode THEN
                fqjVAL = 0
                EXIT FUNCTION
            END IF
        NEXT i%

    LvlPtr = LvlPtr - 1

    ELSE
        ErrorCode = eqjNestedTooDeep
END IF
END FUNCTION

FUNCTION funSolveEquation (InText$)

STATIC Initialized%

IF Initialized% = FALSE THEN
    RESTORE PredefinedFunctionData
    DO
        READ N$, F$
        IF N$ <> "*END*" THEN
            CALL sqjAssignFun(N$, F$, PROTECTED)
        END IF
    LOOP UNTIL N$ = "*END*"

    RESTORE SystemVariableData
    DO
        READ N$
        IF N$ <> "*END*" THEN
            CALL sqjAssignVar(N$, 0, PROTECTED)
        END IF
    LOOP UNTIL N$ = "*END*"

    Initialized% = TRUE
END IF

OPERATOR = ADDSUB + MULTDIV + POWER + LOGICAL
WHITESPACE = " " + CHR$(13) + CHR$(9) + CHR$(10)

ErrorCode = 0
WarningCode = 0
LvlPtr = 0
funSolveEquation = fqjEvaluate(InText$)

END FUNCTION

SUB sjfParse (Word$(), Txt$, Spt$, WordNum%)

Text$ = Txt$
WordNum% = 0
SepLen% = LEN(Spt$)

DO
    WordNum% = WordNum% + 1
    EndWord% = INSTR(Text$, Spt$)
    IF EndWord% THEN
        Word$(WordNum%) = LEFT$(Text$, EndWord% - 1)
        Text$ = MID$(Text$, EndWord% + SepLen%)
    ELSE
        Word$(WordNum%) = Text$
        Text$ = ""
    END IF
LOOP WHILE LEN(Text$)
END SUB

SUB sqjApplyOp (Op$, x, y)

' This is the meat of the operator section, and can be modified to
' includ ANY symbol as an operator, or any two byte symbol combination.
' Any symbol added has to be added to the constant that sets its
' level of precedence.

SELECT CASE Op$
    CASE "-"    ' subtraction
        x = x - y
    CASE "+"    ' addition
        x = x + y
    CASE "*"    ' multiplication
        x = x * y
    CASE "/"    ' division
        IF y <> 0 THEN
            x = x / y
        ELSE
            ErrorCode = eqjDivisionByZero
        END IF
    CASE "\"    ' integer division
        IF y <> 0 THEN
            x = x \ y
        ELSE
            ErrorCode = eqjDivisionByZero
        END IF
    CASE "%"    ' modulo division
        IF y <> 0 THEN
            x = x MOD y
        ELSE
            ErrorCode = eqjDivisionByZero
        END IF
    CASE "^", "**"  ' exponentation
        x = x ^ y
    CASE "}"    ' the rth root of y
        IF y <> 0 THEN
            x = y ^ (1 / x)
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