Html html = Html {
   Head {
      title = "Ceylon: home page";
   };
   Body {
      H2 ( "Welcome to Ceylon, ``user.name``!" ),
      P ( "Now get your code on :)" )
   };
};

Sequence Instantiation

Sequence instantiation creates a new instance of a Sequence|Empty

Usage

Some simple examples using literals to specify the elements:

String[] none = {};
Integer[] ints = {1, 2, 3};
Sequence<String|Integer>|Empty mixed = {1, 2, "a few"};

Description

In some ways, sequence instantiation can be considered a form of invocation with sequenced arguments, and the expressions within the braces may be called the arguments to the instantiation.

Type inference

The typechecker inspects the arguments to a sequence instantiation:

• If there are none then the type is Empty,
• Otherwise it forms the union type of the types of the arguments as the type argument to the Sequence.

This makes type inference (using value) work as you would expect, for example:

// seq has type Sequence<Integer|Boolean|Float>
value seq = {1, true, 3.4}
// none has type Empty
value none = {}

Comprehension

A comprehension provides a convenient way of instantiating a Sequence|Empty from (some of) the (possibly transformed) elements returned from an Iterable.

// get the names of all planets without moons
value moonless = { for (p in planets) if (p.moons.size == 0) p.name };

See the reference on comprehensions for more details.

See also

• Comprehensions can be used to transform, filter and join Iterables in a sequence instantiation.