BBC BASIC: floating point comparison

BBC BASIC
Programming >> Assembly Language >> floating point comparison
http://bbcbasic.conforums.com/index.cgi?board=assembly&action=display&num=1518127371

floating point comparison
Post by Ric on Feb 8^th, 2018, 9:02pm

Evening all, can anyone tell me why this code doesn't work? On the face of it, it gives the right result, but if you change the values of [result] and [result+8] it simply fails!

Help, anyone
Code:

      MODE 7      DIM code% NOTEND AND 2047, code% 2047      DIM result 27      |result      = 11.87655      |(result+8)  = 17.87655      |(result+16) = 0.1      FOR opt% = 0 TO 2 STEP 2        P% = code%        [        OPT opt%        .start          mov                    eax,                       0        mov              DWORD [result+24],               0          fld              QWORD [result]        fld              QWORD [result+16]        faddp                  ST1,                       ST0        fcomp            QWORD [result+8]        fstsw                  ax        wait        sahf        ja                     next_calc        mov              DWORD [result+24],               2        ret          .next_calc          mov                    eax,                       0        fld              QWORD [result]        fld              QWORD [result+16]        fsubp                  ST1,                       ST0        fcomp            QWORD [result+8]        mov                    eax,                       0        fstsw                  ax        wait        sahf        jb                     end        mov              DWORD [result+24],               3        ret          .end        mov              DWORD [result+24],               1        ret        ]      NEXT      CALL start      PRINT !(result+24)

Regards Ric

Re: floating point comparison
Post by Richard Russell on Feb 8^th, 2018, 9:24pm

on Feb 8^th, 2018, 9:02pm, Ric wrote:

Evening all, can anyone tell me why this code doesn't work?

The code requires a *FLOAT 64 but as listed there isn't one. Of course it might simply have been lost in copying the listing into the forum, but it's the first thing I would check.

Richard.

Re: floating point comparison
Post by Ric on Feb 11^th, 2018, 08:31am

Thanks for the swift response Richard, you're right that the *FLOAT command is missing because of transposing into the forum. It turns out as you probably know there is nothing wrong with the code, it was the test on return from the routine that was at fault.

Regards Ric