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diff --git a/pogo.html.markdown b/pogo.html.markdown new file mode 100644 index 00000000..60a83edd --- /dev/null +++ b/pogo.html.markdown @@ -0,0 +1,202 @@ +--- +language: pogoscript +contributors: + - ["Tim Macfarlane", "http://github.com/refractalize"] +filename: learnPogo.pogo +--- + +Pogoscript is a little language that emphasises readability, DSLs and provides excellent asynchronous primitives for writing connected JavaScript applications for the browser or server. + +``` javascript +// defining a variable +water temperature = 24 + +// re-assigning a variable after its definition +water temperature := 26 + +// functions allow their parameters to be placed anywhere +temperature at (a) altitude = 32 - a / 100 + +// longer functions are just indented +temperature at (a) altitude := + if (a < 0) + water temperature + else + 32 - a / 100 + +// calling a function +current temperature = temperature at 3200 altitude + +// this function constructs a new object with methods +position (x, y) = { + x = x + y = y + + distance from position (p) = + dx = self.x - p.x + dy = self.y - p.y + Math.sqrt (dx * dx + dy * dy) +} + +// `self` is similar to `this` in JavaScript with the +// exception that `self` isn't redefined in each new +// function definition +// `self` just does what you expect + +// calling methods +position (7, 2).distance from position (position (5, 1)) + +// as in JavaScript, objects are hashes too +position.'x' == position.x == position.('x') + +// arrays +positions = [ + position (1, 1) + position (1, 2) + position (1, 3) +] + +// indexing an array +positions.0.y + +n = 2 +positions.(n).y + +// strings +poem = 'Tail turned to red sunset on a juniper crown a lone magpie cawks. + Mad at Oryoki in the shrine-room -- Thistles blossomed late afternoon. + Put on my shirt and took it off in the sun walking the path to lunch. + A dandelion seed floats above the marsh grass with the mosquitos. + At 4 A.M. the two middleaged men sleeping together holding hands. + In the half-light of dawn a few birds warble under the Pleiades. + Sky reddens behind fir trees, larks twitter, sparrows cheep cheep cheep + cheep cheep.' + +// that's Allen Ginsburg + +// interpolation +outlook = 'amazing!' +console.log "the weather tomorrow is going to be #(outlook)" + +// regular expressions +r/(\d+)m/i +r/(\d+) degrees/mg + +// operators +true @and true +false @or true +@not false +2 < 4 +2 >= 2 +2 > 1 + +// plus all the javascript ones + +// to define your own +(p1) plus (p2) = + position (p1.x + p2.x, p1.y + p2.y) + +// `plus` can be called as an operator +position (1, 1) @plus position (0, 2) +// or as a function +(position (1, 1)) plus (position (0, 2)) + +// explicit return +(x) times (y) = return (x * y) + +// new +now = @new Date () + +// functions can take named optional arguments +spark (position, color: 'black', velocity: {x = 0, y = 0}) = { + color = color + position = position + velocity = velocity +} + +red = spark (position 1 1, color: 'red') +fast black = spark (position 1 1, velocity: {x = 10, y = 0}) + +// functions can unsplat arguments too +log (messages, ...) = + console.log (messages, ...) + +// blocks are functions passed to other functions. +// This block takes two parameters, `spark` and `c`, +// the body of the block is the indented code after the +// function call + +render each @(spark) into canvas context @(c) + ctx.begin path () + ctx.stroke style = spark.color + ctx.arc ( + spark.position.x + canvas.width / 2 + spark.position.y + 3 + 0 + Math.PI * 2 + ) + ctx.stroke () + +// asynchronous calls + +// JavaScript both in the browser and on the server (with Node.js) +// makes heavy use of asynchronous IO with callbacks. Async IO is +// amazing for performance and making concurrency simple but it +// quickly gets complicated. +// Pogoscript has a few things to make async IO much much easier + +// Node.js includes the `fs` module for accessing the file system. +// Let's list the contents of a directory + +fs = require 'fs' +directory listing = fs.readdir! '.' + +// `fs.readdir()` is an asynchronous function, so we can call it +// using the `!` operator. The `!` operator allows you to call +// async functions with the same syntax and largely the same +// semantics as normal synchronous functions. Pogoscript rewrites +// it so that all subsequent code is placed in the callback function +// to `fs.readdir()`. + +// to catch asynchronous errors while calling asynchronous functions + +try + another directory listing = fs.readdir! 'a-missing-dir' +catch (ex) + console.log (ex) + +// in fact, if you don't use `try catch`, it will raise the error up the +// stack to the outer-most `try catch` or to the event loop, as you'd expect +// with non-async exceptions + +// all the other control structures work with asynchronous calls too +// here's `if else` +config = + if (fs.stat! 'config.json'.is file ()) + JSON.parse (fs.read file! 'config.json' 'utf-8') + else + { + color: 'red' + } + +// to run two asynchronous calls concurrently, use the `?` operator. +// The `?` operator returns a *future* which can be executed to +// wait for and obtain the result, again using the `!` operator + +// we don't wait for either of these calls to finish +a = fs.stat? 'a.txt' +b = fs.stat? 'b.txt' + +// now we wait for the calls to finish and print the results +console.log "size of a.txt is #(a!.size)" +console.log "size of b.txt is #(b!.size)" + +// futures in Pogoscript are analogous to Promises +``` + +That's it. + +Download [Node.js](http://nodejs.org/) and `npm install pogo`. + +There is plenty of documentation on [http://pogoscript.org/](http://pogoscript.org/), inlcuding a [cheat sheet](http://pogoscript.org/cheatsheet.html), a [guide](http://pogoscript.org/guide/), and how [Pogoscript translates to Javascript](http://featurist.github.io/pogo-examples/). Get in touch on the [google group](http://groups.google.com/group/pogoscript) if you have questions! |