I cannot speak to Python, CLisp, or Scheme, but I can explain why Javascript doesn't behave like Perl. Perl detects when a lexical is being closed over and provides a new scratchpad for each closure. This means that your closure factory does exactly what you intend. In Javascript, a new scratchpad is only provided by a function, not a loop. So, to get the equivalent behavior, you have to do the following:
flist = [];
for ( var x = 0; x <= 2; x++ ) {
flist.push( make_closure( x ) );
}
for ( var f in flist ) {
alert( f(2) );
}
function make_closure( x ) { return function (v) { x * v } }
This is a common idiom when creating callbacks for event handlers in JS applications. It's bloody annoying and Eichmann has admitted that this is one of the 5 biggest issues to be addressed in JS2.0 (along with namespaces, non-sucky concatenation vs. addition, etc).
My criteria for good software:
- Does it work?
- Can someone else come in, make a change, and be reasonably certain no bugs were introduced?
Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
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, details, 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, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
| |
For: |
|
Use: |
| & | | & |
| < | | < |
| > | | > |
| [ | | [ |
| ] | | ] |
Link using PerlMonks shortcuts! What shortcuts can I use for linking?
See Writeup Formatting Tips and other pages linked from there for more info.