Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl-Sensitive Sunglasses
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??

Hi Monks,

Why does a list assignment to a list in scalar context return the number of elements on the right side list, but NOT the last element of the left side list that has been assigned values?

I know that:

scalar((1,3,5)) #evaluates to the last element of the list --- 5 if( (5,3,0) ) #evaluates to the last element of the list --- 0, +thus evaluates to FALSE $val=(5,6,7); #evaluates to the last element of the list --- 7

and that:

$ret = (($i, $j, $k)=(5,6,8,9)); #evaluates to the number of el +ements on the right side list --- 4 if( ($k, $v) = ( 1, 0 ) ) #evaluates to the number of el +ements on the right side list --- 2, thus evaluates to TRUE while ( ($key, $value) = each %map ) #still evaluates to the number + of elements on the right side hash

Now check a scalar assignment to a scalar in scalar context: if( $i = 0 ) which will evaluate to the value of $i on the left side, thus evaluate to 0, thus evaluate to FALSE

but consider an example of list assignment above:

if( ($k, $v) = ( 1, 0 ) )
To me, it seems like it should evaluate to the value of list ($k, $v) on the left side just like $i above, thus should evaluate to the last element of list ($k, $v) --- $v, thus evaluate to 0 and at last should evaluate to --- FALSE, although I know the correct answer is it will evaluate to true.

So, the question is: for what purpose are the designing principles of scalar assignment and list assignment both in scalar context completely different? Just for convenience of usage? Isn't that a bit confusing?


In reply to list assignment to list in scalar context by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others imbibing at the Monastery: (7)
    As of 2014-08-21 07:15 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      The best computer themed movie is:











      Results (128 votes), past polls