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CaptainBoing

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Joined: 07/09/2016
Location: United Kingdom
Posts: 2171

Posted: 12:05pm 01 Feb 2018

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In recent fiddlings, I have noticed some problems with the action of VAL(). It certainly looks like a bug but maybe I am misinterpreting things. I have checked the description of VAL in the manual but there is no mention of this kind of behaviour.

It seems to ignore characters for some reason and this affects its basic arithmetic (see example below) that VAL only returns the absolute value of binary and hex strings (probably octal as well but I didn't try) and has errors with different strings.

I was rather expecting a binary string of sixty three 1's and a zero to return a value of -2 but it doesn't, also a value of eight FF's should be -1:

> ? mm.ver
5.0408

> ? val("&b1111111111111111111111111111111111111111111111111111111111111110")
9223372036854775807
> ? val("&hffffffffffffffff")
9223372036854775807 <-- same value for different string

This exhibits the same behaviour if I assign the VAL to a variable (the value is not assessed correctly either):

> x%=val("&b1111111111111111111111111111111111111111111111111111111111111110")
> ? x%
9223372036854775807
> ? bin$(x%,64)
0111111111111111111111111111111111111111111111111111111111111111
>

However if I assign the same binary value directly, it behaves as I expected:

> x%=&b1111111111111111111111111111111111111111111111111111111111111110
> ? x%
-2
>

Any ideas?

Edited by CaptainBoing 2018-02-02

twofingers

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Joined: 02/06/2014
Location: Germany
Posts: 1671

Posted: 01:39pm 01 Feb 2018

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CaptainBoing said Any ideas?

It smells like a bug. Get an exterminator.

Edited by twofingers 2018-02-02

causality ≠ correlation ≠ coincidence

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3308

Posted: 02:15pm 01 Feb 2018

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Good find, thanks.

VAL() works correctly for numbers of 63-bits or less but not with a 64-bit number. I will fix it in the next version.

Geoff

Geoff Graham - http://geoffg.net

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10569

Posted: 02:36pm 01 Feb 2018

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Quote I will fix it in the next version.

What is the bug? I looked at the source and couldn't see anything obvious unless strtoll() is faulty

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3308

Posted: 10:30pm 01 Feb 2018

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Yes, stroll() is faulty. The replacement is:

if(*p == '&') {
p++; iret = 0;
switch(toupper(*p++)) {
case 'H': while(isxdigit(*p)) {
iret = (iret << 4) | ((toupper(*p) >= 'A') ? toupper(*p) - 'A' + 10 : *p - '0');
p++;
}
break;
case 'O': while(*p >= '0' && *p <= '7') {
iret = (iret << 3) | (*p++ - '0');
}
break;
case 'B': while(*p == '0' || *p == '1') {
iret = (iret << 1) | (*p++ - '0');
}
break;
default : iret = 0;
}

Geoff Graham - http://geoffg.net

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