Strings

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In Flax, a string is a simply a series of characters, for example "Foo", "Поссия", and "🐰🐼" are all strings. Programmatically, they are represented by the String type, which is a part of the Foundation library.

Flax Strings are UTF-8 aware, and is able to distinguish between the number of characters versus the number of bytes. The subunit of String, the Character class, is basically a minified string, holding zero or more bytes, defining a UTF-8 codepoint. Despite this, Flax Strings still allow arbitrary indexing via the subscript operator, although the operation happens i O(n) time due to the nature of UTF-8.

As with the rest of Flax, the String type is designed to interoperate as seamlessly as possible with C; Strings can be transparently converted to Int8*, which is equivalent to const char* in C. This is simply an access on the first member of the struct, so care must be taken passing it to mutating functions.

Basic Strings

String Literals

The most straightforward way to use strings in Flax is through a string literal, which is simply a series of characters enclosed in double quotes. String literals can contain Unicode characters, but the source file should be saved as UTF-8 to allow compatibility.

"This is a string."

String literals can be assigned to variables, passed to functions, or otherwise used like a normal expression.

var str = "This is a string."
str = "You've changed."			// this is legal

However, they are immutable, so they cannot be the target of an assignment.

"haha no." = "lol what"			// error

Mutability

The string is a regular type like anything else, so the mutability of a String variable depends on whether it was defined with let/val or var.

let str = "Modify me!"
str += "another!"			// error

Value Behaviour

Flax strings are value-types, meaning that expressions taking a string are given a copy of the original, such that modifying the new string has no effect on the original string.

var string1 = "String One"
var string2 = string1		// the contents of string1 are copied
string2 += "???"

println(string1)			// prints "String One"
println(string2)			// prints "String One???"

The exception is where both the recipient and source of the string are immutable, in which case no copy is made, since it is unnecessary.

let string1 = "String One"
let string2 = string1		// no copy

Characters

Flax allows you to index into a String to get at the characters that make it up. Due to the nature of UTF-8, a Character is actually a series of bytes that come together to represent a Unicode codepoint.

There's really no point in having a separate syntax for characters, so in fact characters are simply initialised using string literals. Thus, an explicit type must be specified, to prevent the variable from being inferred as type String.

let char: Character = "π"