Thursday, March 31, 2005

Partial Replacing Lambda?

Wonder if partial functions are going to replace lambda in python3000.

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().

Maybe 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)

This form should probably be a differently named built-in, but built-ins aren't cheap, and the no argument constructor isn't otherwise meangingful.

Wednesday, March 23, 2005

Humble and Smart

The more you learn about something, the more you realize how little you know about it.

This isn't just philosophy; when people know nothing about a thing, they assume that there's "nothing to it". Then they confidently make decisions based on incomplete information. (It could be because interesting elements exploit the interplay of the simple and the complex. Or it could just be because small details aren't visible at a distance.)

Paradoxically, bright people are more susceptible to this thinking. Bright people are accustomed to quickly understanding ideas outside of their field of expertise, and this understanding is often superior to experts'. A bright person can start to believe (subconsciously) that much of the work in a field is characterized by lack of understanding.

This has ramifications for religious leadership. That religious leaders have insight into issues not technically within the sphere of religious practice is a doctrine of Judaism, and probably other religions as well. It's only logical; following Judaism is about living wisely, and someone with a deeper understanding of Judaism should have attained greater wisdom. In order to be truly wise, however, a person must be aware of his limitations. Maybe this awareness can be achieved by encountering sufficiently dramatic examples (for example the abuse cases involving religious leaders in recent years), or maybe it requires learning a little bit about alot of different things.

(It is troubling to think that G-d confers special wisdom in a way that is completely independent of the natural working of the world. For one thing, thinking that you've got supernatural aid from G-d certainly exacerbates the problem described above. For another, there is no good way to tell when you got it, and when you don't. "Trust in God, but steer away from the rocks", applies here as well.

At any rate, I don't think Judaism encourages completely ignoring the rules of the physical world. There's a gemara in niddah that gives advice about achieving various goals; in each case the gemara advises both acting according to natural way of the world, and also praying for success. In this era characterized by hester panim ("G-d hiding His face"), we certainly shouldn't abdicate the responsibility to do our hishtadlus (effort), especially where other people are involved.)

Friday, March 18, 2005

Idiomatic Python

Programming languages, like human languages, each have their own idiomatic usage. Though there are many different ways to express a single thing, some patterns of expression just feel much more natural.

The idiomatic style of python is beautiful.

Here's an example. You'd like to allow categorizing emails using their subjects, by prefixing the normal subject with the category and a colon. So for a message with subject "game on tuesday", you could use subject "sports: game on tuesday". If no category is specified, you'd like to use "misc". Here's the Pythonic way to do it:
category, subject = headers['Subject'].split(':')
category, subject = 'misc', headers['Subject']

There are a few different features at work here:
  • "It's easier to ask forgiveness than permission"
  • Exceptions are used heavily
  • Language support for collections is simple and easy

Friday, March 11, 2005

"Startups" and Small Businesses

At least since the dot-com bubble, the idea of the startup has been enshrouded in glamor. Most recently Paul Graham posted How to Start a Startup, but his advice is for dot-com-bubble type startups. He suggests that starting a company means compressing a career of 40 years into 4, and assumes that every new business will either flop or become an industry giant.

It could be that when Graham says "startup", he means a company that would rather flop than settle for staying small. Only talking about these startups is strange for a few reasons. Many companies consider themselves successful without making a public stock offering, or being bought out for piles of cash. How about creating a successful small company first, on the way to becoming an industry giant later? And which ideas and strategies are appropriate for which goal? These questions are a lot more relevant today than how to handle a Venture Capitalist imposed CEO.

After all, though more people are employed by big companies, there are many more small companies than big ones.

Wednesday, March 09, 2005

Note to Future Self

Whenever I put something down in an unusual place, there's a strong chance I will "lose" it.

Hopefully when I'm older I'll look back at this note and realize that I'm not going senile.

Tuesday, March 08, 2005

Ipod Shuffle for Lectures

The IPod Shuffle is a wonderful device. One more feature would make it perfect for listening to lecture series (or books on tape or language courses), without bloating its wonderfully simple interface.

The IPod Shuffle should remember the current "song" after it's turned off.

So apparently this is supported for purchases from ITunes and Audible. In order to get it to work with anything else, you have to use faac to create .m4b files.

UPDATE: It works great. If you're using linux, get gnupod, mpg321, and faac. Then you can do something like:
mkdir /mnt/ipod 2>/dev/null
mount /dev/sda1 /mnt/ipod
for mp3 in *.mp3
mpg321 -w $mp3 | faac -b 10 -c 3500 - -o $m4b -m /mnt/ipod $m4b
done -m /mnt/ipod
umount /mnt/ipod
Incidentally, it would be great if gnupod would expose a filesystem-type api to the ipod using fuse.

UPDATE#2: Don't use gnupod; use the iPod shuffle Database Builder.

Thursday, March 03, 2005

Warn of Unsaved Changes Javascript

OK, this will get all the javascript out of my system. This one is intensely useful for web "applications". It warns the user if she tries to leave the form with unsubmitted changes, whether leaving by moving to a different page or by closing the window. It requires a recent firefox or ie browser.
<body onLoad="lookForChanges()" onBeforeUnload="return warnOfUnsavedChanges()">
<select name=a multiple>
<option value=1>1
<option value=2>2
<option value=3>3
<input name=b value=123>
<input type=submit>

var changed = 0;
function recordChange() {
changed = 1;
function recordChangeIfChangeKey(myevent) {
if (myevent.which && !myevent.ctrlKey && !myevent.ctrlKey)
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);

Wednesday, March 02, 2005

Telephone Shell Javascript Widget

Here's some javascript I wrote to coerce uniformly styled phone numbers. If you don't use any punctuation, it defaults to american style. You can enter unrestricted text after the number. You should be able to copy the following into an html file to try it out.
phone #<input onkeypress="return phone_only(event)">

function phone_only(myevent) {
mykey = myevent.keyCode || myevent.which; //ie||netscape
myfield = myevent.srcElement ||; //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;

Tuesday, March 01, 2005

Forms Support in Javascript, not Template

Turns out it's pretty simple to populate forms generically in javascript. This means that your template engine doesn't need special html forms support; you can just use a pair of templating "for" loops to create the javascript data structure. You could even grab the data using xmlhttprequest. Html made the the mess, so html can clean it up.

Here's an example form, followed by the code. You should be able to copy into a file and try it.
<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
<button onClick="populateForm(this.form, {'a':'x0',b:['x1','z1'],'c':['x2','z2']}); return false">Populate</button>
<input type=reset>

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;