Applesoft: Internals--Floating Point Math Package (3 of 3)



                    LOWER LEVEL INTERFACE ROUTINES



FOUT            ED34

FOUT creates an ASCII string in FBUFFR equivalent to the value of FAC.  On

exit Y,A points to the string, which ends with an ASCII null.  FAC is

scrambled.  Use STROUT to print the number.



SNGFLT          E301

SNGFLT converts the unsigned number in Y to a floating point number in FAC.



GIVAYF          E2F2

GIVAYF converts the unsigned number in Y,A to a floating point number in FAC.



FLOAT           EB93

FLOAT converts the signed number in A to a floating point number in FAC.



CONINT          E6FB

CONINT converts FAC into a single byte integer in X and FACLO.  CONINT

normally exits through CHRGET unless FAC is greater than 255 or less than 0,

when it exits via ILLEGAL QUANTITY ERROR.



AYINT           E10C

If FAC is less than +32767 and greater than -32767, then execute QINT.

Otherwise AYINT exits via ILLEGAL QUANTITY ERROR.



QINT            EBF2

Quick greatest integer function.  Leaves INT(FAC) in FACHO,MO,LO signed.

QINT assumes that the absolute value of the FAC is less than 8388608 (2^23rd

power).



GETADR          E752

GETADR converts the number in FAC to a 2 byte, unsigned integer in LINNUM.

When FAC is greater than 65535 or less than -65535, GETADR exits via ILLEGAL

QUANTITY ERROR.



GETNUM          E746

GETNUM fetches a 2 byte number, a comma and an unsigned, single byte number

from TXTPTR.  The first number is stored in LINNUM, while the second is

returned to the X register.  On entry TXTPTR points to the first character of

the formula for the first number.  GETNUM uses FRNUM, GETADR, CHKCOM and

GETBYT.



COMBYTE         E74C

COMBYTE checks for a comma, then fetches an unsigned, single byte number

returned in X.  On entry TXTPTR points to the comma.  COMBYTE uses CHKCOM and

GETBYT.



FRMEVL          DD7B

FRMEVL evaluates the formula at TXTPTR using CHRGET, then leaves the result

in FAC.  On entry, TXTPTR points to the first character of the formula, while

on exit points to the terminator.  "A" does not contain the terminator.  The

format of the temporary result on the stack is:



      The address of the operator routine.

      The floating point temporary result.

      The precedence of the operator.



FRMEVL, the main subroutine for the commands that use formulas, works for

both strings and numbers.  If the formula is a string literal, FRMEVL gobbles

the opening quote, then executes STRLIT and ST2TXT.



FRMNUM          DD67

FRMNUM evaluates the formula at TXTPTR, puts it in FAC, then makes sure the

result is numeric.  On entry TXTPTR points to the first character of the

formula.  FRMNUM exits through TYPE MISMATCH ERROR if the result is a string.



FIN             EC4A

FIN inputs a floating point number into FAC from CHRGET.  FIN assumes the

6502 registers and A were set up by the CHRGET that fetched the first digit.

FIN only operates on numeric constants, not formulas.





Apple Tech Notes





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This information is from the Apple Technical Information Library.



ArticleID: TECHINFO-0000076



19960724 15:55:27.00

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