Ceylon: Sequences and Iterables

	Boolean isOdd(Integer number) => number % 2 != 0;
	/**
	sequence_demo prints
	numbers=1..10
	oddNumbers={ 1, 3, 5, 7, 9 }
	doubledNumbers={ 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 }
	sumOfNumbers=55
	**/
	void sequence_demo() {
	Integer[] numbers = 1..10; //here we use the range shortcut notation
	print("numbers=``numbers``");
	Iterable<Integer> oddNumbers = numbers.filter(isOdd);
	print("oddNumbers=``oddNumbers``");
	Iterable<Integer> doubledNumbers = numbers.map((Integer number) => number * 2);
	print("doubledNumbers=``doubledNumbers``");
	Integer sumOfNumbers = numbers.fold(0, (Integer partial, Integer elem) => partial + elem);
	print("sumOfNumbers=``sumOfNumbers``");
	}

view raw gistfile1.ceylon hosted with ❤ by GitHub

	/**
	Sequences are per definition nonempty and immutable.
	Normally you would start out with the subtype Empty of Sequential (singleton instance empty)
	But looking at the API of Empty we don't see any append or add methods
	So how do we gradually build a sequence?
	There are 2 classes which come to the rescue in this case
	- SequenceBuilder (which has a no-arg constructor) => starts from empty.
	- SequenceAppender (which takes a sequence as constructor parameter) => starts from non empty sequence
	One should however carefully think about whether using a sequencebuilder or sequenceappender is
	really necessary. Most of the times you start out from input which you just have to filter or map.
	**/
	class Manager(shared String name) {}
	void buildSequenceDemo() {
	String[] names = ["John", "Peter", "Sammy"];
	Manager[] managers1 = createManagersFromNames(names);
	//however, more idiomatic would have been
	{Manager*} managers2 = names.map((String name) => Manager(name));
	//we can also use a comprehension
	{Manager*} managers3 = {for (name in names) Manager(name)};
	//or if you really need a sequence instead of an iterable
	Manager[] managers4 = names.map((String name) => Manager(name)).sequence;
	//we can also use a comprehension
	Manager[] managers5 = [for (name in names) Manager(name)];
	}
	Manager[] createManagersFromNames(String[] names) {
	SequenceBuilder<Manager> sb = SequenceBuilder<Manager>();
	for (name in names) {
	sb.append(Manager(name));
	}
	return sb.sequence;
	}
	void appendDemo() {
	/**
	Attention: code below does not work because you have to be explicit about
	names1 being a NON EMPTY sequence
	**/
	//String[] names1 = ["John", "Peter", "Sammy"];
	[String+] names1 = ["John", "Peter", "Sammy"];
	String name = "Ronald";
	String[] combined = SequenceAppender(names1).append(name).sequence;
	}

view raw gistfile1.ceylon hosted with ❤ by GitHub