C:\>perl -le "print 0x2.5;"
25
[download]

LOL, B::Deparse is normally the best way to show such precedence problems, but constant folding is hiding it! :)

D:\>perl -MO=Deparse -E"say 02.5"
use feature 'current_sub', 'evalbytes', 'fc', 'postderef_qq', 'say', '
+state', 'switch', 'unicode_strings', 'unicode_eval';
say '25';
-e syntax OK
[download]

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}

With hindsight, the fact that 25 is a quoted string is a hint.

Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond

Both operators work though.

say '==' if 02.5 == 25;
say 'eq' if 02.5 eq 25;
[download]

prints both == and eq (not that it's surprising either, given perl's seemless conversion between strings and numbers)

prints both == and eq

Yes - though making assumptions about equivalence based on the output of perl's print() function is not a good practice.
For example:

C:\>perl -le "print sqrt(2);"
1.4142135623731

C:\>perl -le "print 'WTF' unless sqrt(2) == 1.4142135623731;"
WTF
[download]

Cheers,
Rob

Sigh! I use . to concatenate strings so infrequently that I just didn't think of it in that role. :-(

Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond

Using Perl to drive moderately high power electronics (400W) does give "smoke testing" a whole other meaning - perhaps closer the the original meaning?

Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond

It's probably overkill, but I'll give it a plug, anyway:

C:\>perl -MMath::MPFR -le "print Math::MPFR->new('2.5', 8);"
2.625
[download]

Math::GMPf is another perl module that can convert octal floating point values to decimal.
Are there any other modules doing that ? (I would expect so, but I haven't checked.)
I couldn't spot any built-in perl functions that will readily do this.

Cheers,
Rob

I expect that trying print 010.5, "\n", which prints 85 might be a clue about what's happening. It seems like octal representation is always interpreted as an int, so you have int(010).5. In which case the dot is the concatenation operator.

You were just unlucky you didn't try

print 09.5, "\n";
[download]

which would have made the problem clearer.

:) Basic debugging checklist ppi_dumper

$ ppi_dumper 2
PPI::Document
  PPI::Statement
    PPI::Token::Word    'print'
    PPI::Token::Whitespace      ' '
    PPI::Token::Number::Octal   '02'
    PPI::Token::Number::Float   '.5'
  PPI::Token::Whitespace        '\n'
[download]

:O you've found a bug :D an old one https://github.com/adamkennedy/PPI/issues/165

"25 Amps is not at all the same thing as 2.5 Amps!"

I have definitely and literally found out the hard way a couple of times that unexpected results can do real damage when dealing with real electricity :)

real damage when dealing with real electricity

"Toy" electricity is already sufficient for real damage, see Re: I came, I saw, I .... But yes, "real" electricity has more interesting results and significantly more magic smoke escaping. See this story from wired.com and this embedded video of a 27 ton generator connected to the power grid out of phase.

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

What!! You mean reality is not a video game with a Restart Button ? Yikes!

print 02.5, "\n";
print 02.9, "\n";
print 025, "\n";
[download]

C:\>perl -wle "print 02.5p+0;"
2.625

C:\>perl -wle "print 02.9p+0"
Bareword found where operator expected at -e line 1, near "9p"
        (Missing operator before p?)
Unquoted string "p" may clash with future reserved word at -e line 1.
syntax error at -e line 1, near "9p"
Execution of -e aborted due to compilation errors.

C:\>perl -wle "print 025p+0"
21
[download]