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diff --git a/pogo.html.markdown b/pogo.html.markdown new file mode 100644 index 00000000..6c619e0b --- /dev/null +++ b/pogo.html.markdown @@ -0,0 +1,258 @@ +--- +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. + +# variables + +defining a variable + +``` +water temperature = 24 +``` + +re-assigning a variable after its definition + +``` +water temperature := 26 +``` + +## functions + +functions allow their parameters to be placed anywhere + +``` +temperature at (altitude) altitude = 32 - altitude / 100 +``` + +longer functions are just indented + +``` +temperature at (altitude) altitude := + if (altitude < 0) + water temperature + else + 32 - altitude / 100 +``` + +calling a function + +``` +current temperature = temperature at 3200 altitude +``` + +## objects and methods +this function constructs a new object + +``` +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) +} +``` + +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.' + +// Allen Ginsburg +``` + +interpolation + +``` +outlook = 'amazing!' +console.log "the weather tomorrow is going to be #(outlook)" +``` + +## regular expressions + +``` +r/(\d+)m/ +``` + +## 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) +``` + +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 () +``` + +# more on functions + +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 + +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 + +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 + +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)" +``` + +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! |