Bob Nystrom
6ed15da597
Add `^category` front matter to all language, types, and reference doc pages for site navigation restructuring. Replace `:::wren` and `:::java` code block annotations with `:::dart` across multiple files. Create new stub pages for core-libraries, embedding-api, and contributing under the reference category. Remove the old embedding and getting-involved stub pages.
1.9 KiB
^title Values ^category types
Values are the built-in object types that all other objects are composed of. They can be created through literals, expressions that evaluate to a value.
Booleans
A boolean value represents truth or falsehood. There are two boolean literals,
true and false. Its class is Bool.
Numbers
Like other scripting languages, Wren has a single numeric type: double-precision floating point. Number literals look like you expect coming from other languages:
:::dart
0
1234
-5678
3.14159
1.0
-12.34
Numbers are instances of the Num class.
Strings
Strings are chunks of text. String literals are surrounded in double quotes:
:::dart
"hi there"
A couple of escape characters are supported:
:::dart
"\n" // Newline.
"\"" // A double quote character.
"\\" // A backslash.
Their class is String.
Ranges
A range is a little object that represents a consecutive range of numbers. They don't have their own dedicated literal syntax. Instead, the number class implements .. and ... operators to create them:
:::dart
3..8
This creates a range from three two eight, including eight itself. If you want a half-inclusive range, use ...:
:::dart
4..6
This creates a range from four to six not including six itself. Ranges are commonly used for looping over a sequences of numbers, but are useful in other places too. You can pass them to a list's subscript operator to return a subset of the list, for example:
:::dart
var list = ["a", "b", "c", "d", "e"]
var slice = list[1..3]
IO.print(slice) // ["b", "c", "d"]
Null
Wren has a special value null, which is the only instance of the class Null.
(Note the difference in case.) It functions a bit like void in some
languages: it indicates the absence of a value. If you call a method that
doesn't return anything and get its returned value, you get null back.