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Typesafe Records for Ceylon

The example demonstrates the use of Ceylon's powerful type system to define typesafe heterogenous maps, otherwise known as record types.

• records.ceylon defines a tiny library for creating records
• keys.ceylon defines example typesafe keys

gavinking

"A generic function that produces a memoized version
 of the given [[function|fun]]. Works for any function 
 arity."
Callable<Return,Args> memoize<Return,Args>(Callable<Return,Args> fun) 
        given Args satisfies Anything[] {
    value cache = HashMap<Args,Return&Object|Finished>();
    function callFun(Args args) {
        //we'll use finished as a convenient
        //unit value to represent the case
        //that the function returned null

gavinking

Ceylon Solar System Example

This little example application demonstrates the use of Ceylon as an alternative to client-side JavaScript. In particular, the example shows:

• a simple, typesafe, object-oriented program,
• dependence on an external [cross-platform math module][xmath] written in Ceylon and hosted on

gavinking

import ceylon.collection {
    ArrayList
}

"Create a typesafe proxy for the given [[instance]], that
 intercepts method calls and attribute evaluations."
Instance proxy<Instance>(Instance instance)(call, get) {

    "Intercepts method invocations. Delegate to the method
     of [[target]] by calling `method(args)`."

gavinking

import ceylon.time { Instant, DateTime }

shared void run() {
    dynamic {
        //create a JavaScript Date
        dynamic date = Date();
        print(date);
        //convert it to a Ceylon DateTime
        DateTime dt = Instant(date.getTime()).dateTime();
		print(dt);

gavinking

Ceylon Services Example

This tiny example demonstrates the use of Ceylon [service providers][] in the JavaScript environment. Service providers are an abstraction of, and [interoperate][] with, Java's [service loaders][], but are not tied to the Java platform, and can even work cross-platform.

gavinking

/*
  Demonstrates how to do monadic-style processing of
  optional values in Ceylon. Represents an optional
  type by boxing non-null values as singletons, and
  the null value as the empty sequence. Monadic
  operations are inherited from the stream interface,
  with the caveat that m.flatMap(f) must be written 
  as m.flatMap(lift(f)) or as m.map(f).coalesced.
  
  For the record: this is not idiomatic Ceylon. In

gavinking

shared Map<Key,Item> reduceByKey<Key,Item>(
	{<Key->Item>+} stream, 
	Item accumulating(Item x, Item y)) 
		given Key satisfies Object 
		given Item satisfies Object
		=> stream.summarize(Entry.key, 
			(Item? partial, entry) 
					=> let (_->item = entry) 
					if (exists partial) 
					then accumulating(partial, item) 

gavinking

Description	Location	Resource	Path	Type
Access restriction: The constructor 'CoreException(IStatus)' is not API (restriction on required library '/Users/gavin/ceylon-ide-eclipse/plugins/com.redhat.ceylon.eclipse.ui/target/repo/plugins/org.eclipse.equinox.common-3.6.200.v20130402-1505.jar')	line 123	AndroidBuildHookProvider.java	/com.redhat.ceylon.eclipse.android.plugin/src/com/redhat/ceylon/eclipse/android/plugin	Java Problem
Access restriction: The constructor 'Status(int, String, int, String, Throwable)' is not API (restriction on required library '/Users/gavin/ceylon-ide-eclipse/plugins/com.redhat.ceylon.eclipse.ui/target/repo/plugins/org.eclipse.equinox.common-3.6.200.v20130402-1505.jar')	line 123	AndroidBuildHookProvider.java	/com.redhat.ceylon.eclipse.android.plugin/src/com/redhat/ceylon/eclipse/android/plugin	Java Problem
Access restriction: The constructor 'Status(int, String, String, Throwable)' is not API (restriction on required library '/Users/gavin/ceylon-ide-eclipse/plugins/com.redhat.ceylon.ecl

gavinking

import ceylon.collection {
    LinkedList
}
import ceylon.math.float {
    sin,
    pi
}


"Map a function of arity `n` to a stream of values. In each