partial(operator.add, 1) isn't such an attractive substitute for lambda x: x+1, but that's more about operator than it is about partial().partial()+1 should be supported using operator overloading. It'd be especially nice to be able to do partial()+x+y instead of partial(operator.add, x+y)try:
category, subject = headers['Subject'].split(':')
except:
category, subject = 'misc', headers['Subject']
mkdir /mnt/ipod 2>/dev/nullIncidentally, it would be great if gnupod would expose a filesystem-type api to the ipod using fuse.
mount /dev/sda1 /mnt/ipod
for mp3 in *.mp3
do
m4b=${mp3%.*}.m4b
mpg321 -w $mp3 | faac -b 10 -c 3500 - -o $m4b
gnupod_addsong.pl -m /mnt/ipod $m4b
done
mktunes.pl -m /mnt/ipod
umount /mnt/ipod
<body onLoad="lookForChanges()" onBeforeUnload="return warnOfUnsavedChanges()">
<form>
<select name=a multiple>
<option value=1>1
<option value=2>2
<option value=3>3
</select>
<input name=b value=123>
<input type=submit>
</form>
<script>
var changed = 0;
function recordChange() {
changed = 1;
}
function recordChangeIfChangeKey(myevent) {
if (myevent.which && !myevent.ctrlKey && !myevent.ctrlKey)
recordChange(myevent);
}
function ignoreChange() {
changed = 0;
}
function lookForChanges() {
var origfunc;
for (i = 0; i < document.forms.length; i++) {
for (j = 0; j < document.forms[i].elements.length; j++) {
var formField=document.forms[i].elements[j];
var formFieldType=formField.type.toLowerCase();
if (formFieldType == 'checkbox' || formFieldType == 'radio') {
addHandler(formField, 'click', recordChange);
} else if (formFieldType == 'text' || formFieldType == 'textarea') {
if (formField.attachEvent) {
addHandler(formField, 'keypress', recordChange);
} else {
addHandler(formField, 'keypress', recordChangeIfChangeKey);
}
} else if (formFieldType == 'select-multiple' || formFieldType == 'select-one') {
addHandler(formField, 'change', recordChange);
}
}
addHandler(document.forms[i], 'submit', ignoreChange);
}
}
function warnOfUnsavedChanges() {
if (changed) {
if ("event" in window) //ie
event.returnValue = 'You have unsaved changes on this page, which will be discarded if you leave now. Click "Cancel" in order to save them first.';
else //netscape
return false;
}
}
function addHandler(target, eventName, handler) {
if (target.attachEvent) {
target.attachEvent('on'+eventName, handler);
} else {
target.addEventListener(eventName, handler, false);
}
}
</script>
<form>
phone #<input onkeypress="return phone_only(event)">
</form>
<script>
function phone_only(myevent) {
mykey = myevent.keyCode || myevent.which; //ie||netscape
myfield = myevent.srcElement || myevent.target; //ie||netscape
if (mykey == 8) //backspace (netscape only)
return true;
f = myfield.value;
g = myfield.value;
ndigits = f.replace(/-/,'').length;
ngroupdigits = g.replace(/.*-/,'').length;
if (ndigits == 0) {
if (50 <= mykey && mykey <= 57) { //2-9, can't start with 0 or 1
return true;
} else {
return false;
}
} else if (ndigits <= 7) { //only need 2 hyphens: 123-456-7
if (32 <= mykey && mykey <= 47 && ngroupdigits != 0) { //punctuation
myfield.value += "-";
return false;
} else if (48 <= mykey && mykey <= 57) { //0-9
if ((ngroupdigits % 4) == 3) {
myfield.value += "-";
}
return true;
} else {
return false;
}
} else {
return true;
}
}
</script>
<form>
<input name=a>
<input name=b type=checkbox value=x1>
<input name=b type=checkbox value=y1>
<input name=b type=checkbox value=z1>
<select name=c multiple>
<option value=x2>X2
<option value=y2>Y2
<option value=z2>Z2
</select>
<button onClick="populateForm(this.form, {'a':'x0',b:['x1','z1'],'c':['x2','z2']}); return false">Populate</button>
<input type=reset>
</form>
<script>
function populateForm(myForm,myHash) {
for (var k in myForm) {
if (!(k in myForm) || !(k in myHash)) continue;
if (typeof myHash[k] == 'string')
myHash[k] = [myHash[k]];
if (myForm[k].type == 'text') {
myForm[k].value = myHash[k][0];
} else {
var field = 'type' in myForm[k] && myForm[k].type.match('^select') ? 'selected' : 'checked';
var selected = Array();
for (var i=0; i<myHash[k].length; i++)
selected[myHash[k][i]] = 1;
for (var i=0; i<myForm[k].length; i++)
myForm[k][i][field] = myForm[k][i].value in selected;
}
}
}
</script>
Does a given piece of information belong in a book, an academic paper, a weekly magazine article, an editorial, a letter to the editor? The internet makes the distinctions increasingly irrelevant.
A web page is an expression of an idea that is universally available (at least theoretically). It's easy to refer to, and easy to maintain. The internet will one day provide a distributed wikipedia, in which every idea has a URI and page(s) containing all public human knowledge of that idea.
Traditional bibliographies are klunky in comparison. It will be possible to link a given piece of information with every other piece of information on which it relies. That metadata will itself be data, subject to easy analysis.
The core language has so many features that even the greatest perl wizard does not know them all. Find a wizard and ask him how many of the following features from the core language he understands (without consulting the manual).
split(' ') vs split(/ /) vs split('') vs split(//) $x{'a', 'b'} vs @x{'a', 'b'} $[ = 3
[{foo => 1, bar => 2}, "FOO", "BAR"] And here's a realistic example of idiomatic perl:
sub with_gs_acct_check_digit{"$_[0]-".substr(10-(map$_[2]+=$_,map/\d/?$_[1]++%2?split'',$_*2:$_:0,split'',$_[0])[-1]%10,-1)} Since these features usually address a real need, they can be very tempting to use. Even if someone were to do the work to specify a sane perl subset, there is no tool to enforce its use. Often a perl expert isn't aware that the language features that he uses are obscure or difficult for the nonexpert to understand.
Perl's fast feature accretion is a direct result of its core design philosophy, "There's More Than One Way To Do It".
Since every new feature is encoded using a fixed set of operators, very few errors actually cause a compiler error.
print "Strings are equal\n" if "abba" == "baba";
Every perl expression has several entirely different results depending on its "context", the code in which the expression occurs. The following example will trip up even experienced perl coders:
sub myPrint($) {
my $arg = @_;
print "the first argument is $arg ?\n";
} Many commonly used features are unsafe. The "use strict" directive only catches the most blatant.
For example, one of perl's major conveniences is the $_ short-hand for referring to the current index of a loop. The following is great way to print upper-cased versions of some strings.
@t = qw( ibm dell msft );
for (@t) {
print uc "$_\n"
}
However, if you want to instead use a different function in place of "uc", this code may fail in mysterious ways. Functions called in the body of the loop can alter what the $_ reference refers to, and neither the caller nor the callee may realize the danger.
Exception support is inconsistent and dangerous. When most function fail, they just return false and sometimes an error code. Other functions expect to be called in "eval blocks", and will otherwise cause the entire program to terminate (e.g. mkpath from File::Path)
Another example is auto-vivification, or the on-the-fly creation of datastructures. For the following data structure:
use strict;
my %myhash1=( "a"=>1, "b"=>2 );
my %myhash2 =( "myhash1"=>\%myhash1, "c"=>3, "d"=>4 );
Perl will properly catch the error:
$myhash3{c}++; # %myhash3 is not defined But will happily allow:
$myhash2{myhash3}{c}++; # a new hash will be created! Nested data structures in perl are unwieldy. They require using references, and most people are confused by references.