Re: Sorted Code

On Fri, 14 Dec 2001, Ilmari Karonen wrote:

> But surprisingly enough, the following
> also outputs "- syntax OK" for at least versions 5.005_03 and 5.7.1:
> 
>   perl -e 'print map chr, 0, 4 .. 255' | perl -c
> 
> That's a total of 253 out of 256 characters, which seems unbeatable.
> 
> No, I've no idea why that works.  Explanations gladly accepted.

Erm, according to the ascii man page:

       Oct   Dec   Hex   Char           Oct   Dec   Hex   Char
       ------------------------------------------------------------
       000   0     00    NUL '\0'       100   64    40    @
       001   1     01    SOH            101   65    41    A
       002   2     02    STX            102   66    42    B
       003   3     03    ETX            103   67    43    C
   ->  004   4     04    EOT            104   68    44    D
       005   5     05    ENQ            105   69    45    E
       006   6     06    ACK            106   70    46    F

This is EOT, End Of Text (aka ^D). So your script is in fact \0.

I guess perl -O=Deparse returns '???' (a constant in void context:
optimized away)

$ perl -e 'print map chr, 0, 4 .. 255' | perl -MO=Deparse
- syntax OK

Mmm. So I am wrong about the NUL char. But I am pretty confident about ^D.

In fact it's 

perl -MO=Deparse -e '\0'
'???';
- syntax OK

that does what I thought.


You can test the embedded ^D stuff with this file:

print "ok";
^D  <- embedded Ctrl-D: one char. Use ^V^D to input this in vi.
print "nok";

$ perl file
ok

-- 
 Philippe "BooK" Bruhat

 The friends we make and the friends we lose are all better than the friends
 who want to make us lose.        (Moral from Groo The Wanderer #1 (Pacific))

• Sorted Code by Alistair.McGlinchy
• Re: Sorted Code by Philippe 'BooK' Bruhat
• Re: Sorted Code by Piers Cawley
• Re: Sorted Code by Jeff 'japhy' Pinyan
• Re: Sorted Code by Ilmari Karonen
• Re: Sorted Code by Jeff 'japhy' Pinyan
• Re: Sorted Code by Ilmari Karonen