2.4 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.
All values are immutable—once created, they do not change. The number
3 is always the number 3. The string "frozen" can never have its
character array modified in place.
Booleans
A boolean value represents truth or falsehood. There are two boolean literals,
true and false. Their 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 stored as UTF-8. Their class is String. String
literals are surrounded in double quotes:
:::dart
"hi there"
A handful of escape characters are supported:
:::dart
"\"" // A double quote character.
"\\" // A backslash.
"\a" // Alarm beep. (Who uses this?)
"\b" // Backspace.
"\f" // Formfeed.
"\n" // Newline.
"\r" // Carriage return.
"\t" // Tab.
"\v" // Vertical tab.
A \u followed by four hex digits can be used to specify a Unicode code point.
Ranges
A range is a little object that represents a consecutive range of integers.
They don't have their own dedicated literal syntax. Instead, the number class
implements the .. and ... operators to create
them:
:::dart
3..8
This creates a range from three to 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 iterating 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.