3.3 KiB
^title Values
Values are the built-in atomic 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:
:::wren
0
1234
-5678
3.14159
1.0
-12.34
Numbers are instances of the Num class.
Strings
A string is an array of bytes. Typically, they store characters encoded in UTF-8, but you can put any byte values in there, even zero or invalid UTF-8 sequences. (You might have some trouble printing the latter to your terminal, though.)
String literals are surrounded in double quotes:
:::wren
"hi there"
A handful of escape characters are supported:
:::wren
"\0" // The NUL byte: 0.
"\"" // 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:
:::wren
System.print("\u0041\u0b83\u00DE") //> AஃÞ
A capital \U followed by eight hex digits allows Unicode code points outside
of the basic multilingual plane, like all-important emoji:
:::wren
System.print("\U0001F64A\U0001F680") //> 🙊🚀
A \x followed by two hex digits specifies a single unencoded byte:
:::wren
System.print("\x48\x69\x2e") //> Hi.
Strings are instances of class 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 the .. and ... operators to create them:
:::wren
3..8
This creates a range from three to eight, including eight itself. If you want a
half-inclusive range, use ...:
:::wren
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:
:::wren
var list = ["a", "b", "c", "d", "e"]
var slice = list[1..3]
System.print(slice) //> [b, c, d]
Their class is Range.
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.