Lexical structure

This page covers the tokens: comments, identifiers, keywords, number and boolean literals, and statement separators. String literals have their own page, Strings.

Comments

// starts a comment that runs to the end of the line. /* ... */ runs until the next */, across any number of lines. It does not nest: the first */ closes the comment, even when an inner /* came after the outer one.

// a line comment runs to the end of the line
let reloadSeconds = 2 // trailing comments work the same way

/* a block comment
   can span several lines; it does not nest */
let squadStrength = 4

println(reloadSeconds + squadStrength)

6

Identifiers and keywords

An identifier starts with a letter or _, followed by any number of letters, digits or _. Quirrel is case sensitive, so squad, Squad and SQUAD are three different names.

These words are reserved and cannot be used as an identifier. Each links to the section that explains it.

Two entries in this list are special:

• not only appears directly before in, as the compound operator x not in t. There is no standalone not expr; write !expr for that.
• clone, switch, case and default are reserved only while the language feature they belong to is turned on. A compiler directive can turn the feature on or off for a unit. When the feature is off, the word parses as an ordinary identifier: #forbid-clone-operator lets you declare function clone(x) { ... }.

async and await mark an asynchronous function and wait for a value in it. See async and await.

Numbers

An integer is decimal (30) or hexadecimal (0x1E, up to 16 hex digits). A leading 0 before another digit is a compile error; octal literals are not supported. A character between single quotes, such as 'A', is also an integer literal. Its value is the one byte between the quotes, or the one byte that an escape such as '\n' produces. Anything that is not exactly one byte is an error.

A float needs a fractional part, an exponent, or both: 1.5, 1.5e3, 1e-3. There is no bare leading dot: write 0.5, not .5.

An underscore may appear between digits anywhere in a number, decimal, hex or float. It has no effect on the value: 123_456, 0xFF_00, 1_000.25 are the same values as without the underscores.

// decimal and hex integers; '_' is an ignored digit separator
let magazineCapacity = 30
let ammoCrateId = 0xFF00_A1

// a char literal is just an integer: the byte value of one character
let ammoTypeCode = 'A'

// a float takes a fraction, an exponent, or both
let dropChance = 0.05
let starShellRange = 3.5e3

println("magazineCapacity =", magazineCapacity)
println("ammoCrateId =", ammoCrateId)
println("ammoTypeCode =", ammoTypeCode)
println("dropChance =", dropChance)
println("starShellRange =", starShellRange)

magazineCapacity = 30
ammoCrateId = 16711841
ammoTypeCode = 65
dropChance = 0.05
starShellRange = 3500

true, false, null

true and false are the two bool values. null is its own type with one value. It is not 0, false, or an empty string. See Values and types for how equality treats it.

__FILE__ and __LINE__

__FILE__ and __LINE__ are keywords, not variables. The compiler replaces each with a literal at the position where it appears: __FILE__ with the path being compiled, and __LINE__ with the number of that line. The substitution happens where the token is in the source, so __LINE__ inside a function reports the line where it is written, not the line of the call.

function reportLine() {
  return __LINE__ // the line of this statement, not of the call site
}

println("__LINE__ =", __LINE__)
println("reportLine() =", reportLine())
println("type(__FILE__) =", type(__FILE__))

__LINE__ = 5
reportLine() = 2
type(__FILE__) = string

Statement separators

A newline ends a statement. ; also ends a statement, and lets two statements share one line. Both work only at a point where the current statement can end. A trailing operator, an open (, or a trailing , keeps the parser inside the same statement, and it continues onto the next line to find the rest of the expression.

// ';' lets two statements share a line; a lone newline also ends one
let ammoLeft = 5; let magazineSize = 30

// a newline does not end a statement while an operator leaves it dangling
let totalRounds = ammoLeft +
  magazineSize

println(totalRounds)

35

# is a directive, not a comment

A line starting with # is not a comment. It is a compiler directive, and it changes how the rest of the file compiles. Do not confuse it with //.