Quads: displaying all 19 digits

[Francois Roy]

I have noticed the limitation of Str$() to display only 18
digits of precision, but no such mention is made for Format$(),
although I can't seem to get an accurate 19-digit display of
large Quad values, even with a "##################0" mask.

Is there any way at all to display the full precision of a
large Quad value?

[Lance Edmonds]

STR$() only works up to 18 digits. FORMAT$(QuadVar, ",") works up to 19 digits ok, and the alternative format string with a single pound symbol "#" works too.

Here is a small PB/CC example to get you going:

FUNCTION PBMAIN
    DIM a AS QUAD
    a = &H7FFFFFFFFFFFFFFF
    PRINT a
    PRINT STR$(a,18)
'    PRINT STR$(a,19)
    PRINT FORMAT$(a, ",")
    PRINT FORMAT$(a, "#")
    WAITKEY$
END FUNCTION

On a related topic, be sure to read the FAQ on 80 bit floating point precision - see the FAQ forum for details.

------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Francois Roy]

That's what I assumed too, but running this simple test
told me that some rounding is taking place somewhere.

You would expect the three values to be different on output:

FUNCTION PBMAIN
DIM Q AS QUAD
Q=&H7FFFFFFFFFFFFFFF
PRINT FORMAT$(Q,"#")
Q=&H7FFFFFFFFFFFFFFE
PRINT FORMAT$(Q,"#")
Q=&H7FFFFFFFFFFFFFFD
PRINT FORMAT$(Q,"#")
END FUNCTION

but here is the output I get:

9223372036854776320
9223372036854776320
9223372036854776320

[Eric Pearson]

Interesing. I applied the 80-bit patch from the FAQ forum to that program and I still get incorrect results.

9223372036854775810
9223372036854775810
9223372036854775800

-- Eric


------------------
Perfect Sync: Perfect Sync Development Tools
Email: mailto:[email protected][email protected]</A>

[Eric Pearson]

this code shows that the 18-digit limitation is in format$, not the quad math operation. and it demonstrates an easy workaround for using format$ with huge values...

<font face="courier new, courier" size="3"><pre>
$register none
$compile exe
function pbmain
dim xyz as local integer
dim q1 as local quad
dim q2 as local quad
'apply 80-bit precision patch
xyz = 0
asm fstcw xyz
asm or xyz, &b0000001100000000%
asm fldcw xyz
'perform the test
q1=&h7fffffffffffffff???
q2=&h7ffffffffffffffe???
print "direct:"
print format$(q1,"#")
print format$(q2,"#")
print
print "difference between values = ";q1-q2
print
print "workaround:"
print format$(q1\100000);format$(q1 mod 100000)
print format$(q2\100000);format$(q2 mod 100000)
waitkey$
end function
[/CODE]

here is a link to the 80-bit faq:

http://www.powerbasic.com/support/pb...hread.php?t=45

-- eric
------------------
perfect sync: perfect sync development tools
email: mailto:[email protected][email protected]</a>



[this message has been edited by eric pearson (edited may 17, 2000).]