Hi again all,
On Sat, Dec 13, 2008 at 14:34, Arnar Birgisson <[email protected]> wrote:
> As for permuting arguments, I have some ideas.. let me think about them a bit.
Here is an implementation of partial that does out-of-order arguments,
both via unnumbered placeholders and numbered ones (see the function
test() for examples):
// I'm also attaching an html file that you can load in your browser
to see it in action.
function p() {
var args = Array.prototype.slice.call(arguments);
appendChildNodes('logpane', DIV(null, args.join(', ')));
}
function _(n) {
return {'__argument_index': n};
}
var invalidNumberOfArgs = new Error("Number of given arguments does
not match number of unknown arguments.");
var mixingNumberedWithUnnumbered = new Error("Cannot mix numbered
argument placeholders with numbered ones.");
var invalidNumberedPlaceholders = new Error("Numbered placeholders
must be sequential (i.e. no gaps) starting from 0 or 1.");
function partial() {
var args = Array.prototype.slice.call(arguments);
var f = args.shift();
var unnumbered = filter(MochiKit.Base.partial(operator.seq, _), args).length;
var indexes = map(itemgetter('__argument_index'), filter(function (a) {
return typeof a == 'object' && '__argument_index' in a;
}, args));
if (unnumbered > 0 && indexes.length > 0) {
throw mixingNumberedWithUnnumbered;
}
if (indexes.length == 0) {
return function() {
if (arguments.length != unnumbered) {
throw invalidNumberOfArgs;
}
var passed = Array.prototype.slice.call(arguments);
var filled = map(function (a) {
if (a === _) {
return passed.shift();
} else {
return a;
}
}, args);
return f.apply(this, filled);
}
} else {
// some sanity checks
var sorted = indexes.slice(0);
sorted.sort();
if (sorted[0] == 1) {
indexes = map(function (x) {return x-1;}, indexes);
sorted = map(function (x) {return x-1;}, sorted);
} else if (sorted[0] != 0) {
throw invalidNumberedPlaceholders; // must start with 0 or 1
}
// make sure there are no gaps
if (!every(izip(count(), sorted), function (pair) { return
pair[0] == pair[1]})) {
throw invalidNumberedPlaceholders; // can't have gaps
}
return function() {
if (arguments.length != indexes.length) {
throw invalidNumberOfArgs;
}
var passed = Array.prototype.slice.call(arguments);
var i = 0;
var filled = map(function (a) {
if (typeof a == 'object' && '__argument_index' in a) {
return passed[indexes.shift()];
} else {
return a;
}
}, args);
return f.apply(this, filled);
}
}
}
function test() {
p('start');
var x = partial(p, "one", _, "three");
x('two');
x = partial(p, _, _, "three", _);
x('one', 'two', 'four');
x = partial(p, _);
x('one');
x = partial(p, 'one');
x();
x = partial(p, _(2), _(1));
x('two', 'one');
// for convenience:
function flip(f) { return partial(f, _(2), _(1)); }
x = flip(p);
x('two', 'one');
// can also be zero based
x = partial(p, _(1), _(0));
x('two', 'one');
x = partial(p, 'one', _(3), 'three', _(1), 'five', _(2));
x('four', 'six', 'two');
p('done');
}
addLoadEvent(test);
cheers,
Arnar
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