A literal is an object with its own special syntax that allows it to be inserted directly into code. Lasso supports string, boolean, integer, decimal, tag, staticarray, and generateSeries literals, the words null and void, and comments.

The method for expressing these literals is largely similar to other scripting languages. For example, an integer literal is expressed, as one would expect, by simply using the numeral in the source text. 23 is an example of an integer literal.

String Literals

Lasso supports two kinds of string literals: quoted and ticked. Quoted strings can contain escape sequences, while ticked strings cannot. Both quoted and ticked string literals can contain line breaks, and produce the same type of string objects. The differences between the two types of literals are handled entirely during parsing. All strings in Lasso are Unicode strings, which means that a string can contain any of the characters available in Unicode.

Quoted Strings

The first kind of string literal is a quoted string, which is a series of zero or more characters surrounded by either single or double quotes. If a string literal begins with a single quote, then it must end with a single quote. The same holds for a string literal that begins with a double quote; it must end with a double quote.

'This is a string literal'
"This is also a string literal"

Within this type of string literal, the backslash character (\x5C) is interpreted as an escape character. This means that when a backslash is encountered in a string literal, it changes the meaning of the immediately following character(s). For example, a backslash is required in order to create a string literal that contains the quote character that surrounds the string.

'This is a \'string literal\' with quotes'
"This is also a \"string literal\" with quotes"

Note that a backslash is not required in order to insert the alternate quote type into a string literal. For example, a double-quoted string can contain a single quote without having to escape it.

"Escaping this single quote isn't required"

A backslash is also required in order to insert a literal backslash into a string. In order to embed a backslash into a string, two backslashes must be used.

'This string literal has a backslash \\ in it'

A backslash followed by an end-of-line (a literal line feed or carriage return or carriage return/line feed pair) will cause that end-of-line and all following literal whitespace to be removed from the resulting string. The string resumes starting with the first encountered non-whitespace character. This sort of escape sequence can be useful for preserving the visual formatting of a string literal while removing the characters used to achieve that formatting from the resulting string.

'This string \
       had a break in it'
// => This string had a break in it

The backslash can also be used to insert Unicode characters represented either by hex code, or by character name. Where the Unicode character name is used, the name must be the official Unicode name for that character, enclosed between a set of colons. Additionally, it is an error to use an unrecognized character name.

Also supported are a series of commonly used escape sequences. The following table shows all of the permissible escape sequences.

Supported String Escape Sequences
Escape Sequence Value Description
\xdd Unicode character 1–2 hex digits
\udddd Unicode character 4 hex digits
\Udddddddd Unicode character 8 hex digits
\ddd Unicode character 1–3 octal digits
\:NAME: Unicode character Unicode character name
\a 0x07 bell
\b 0x08 backspace
\e 0x1B escape
\f 0x0C form feed
\n 0x0A line feed
\r 0x0D carriage return
\t 0x09 tab
\v 0x0B vertical tab
\" 0x22 double quote
\' 0x27 single quote
\? 0x3F question mark
\\ 0x5C backslash
\<end-of-line> none escaped whitespace

Ticked Strings

A ticked string is a series of zero or more characters surrounded by a pair of backticks (\x60). Within a ticked string, the backslash character holds no special meaning. Ticked strings do not recognize any escape sequences, and this can make them particularly useful when using regular expressions which often require many backslashes. (Using regular quoted strings, the backslashes would themselves have to be doubled.) The caveat for this is that a literal backtick character cannot appear within a ticked string.

`This is a ticked string`
`A ticked string can contain 'single quotes', "double quotes",
\backslash characters\ and more - anything except backticks!`

Boolean Literals

A boolean is an object that is either “true” or “false”. Lasso supports the creation of these objects by using the word true or false directly in the source code.

type boolean

Casts a value to a boolean value. Only the following objects and values evaluate to “false”; all others are “true”:


Although the empty string evaluates to “false”, this functionality is deprecated. Instead, call string->size to check for empty strings.

Integer Literals

An integer is a whole number. Integers can be positive or negative, and Lasso puts no limit on the size of an integer. Integers consist of the digits 0 through 9 and can be written directly into the source code.


Integers can also be written using hexadecimal notation. Hexadecimal integers begin with a zero followed by an upper or lowercase “x” followed by one or more hexadecimal digits (0–9 and A–F). Either upper or lowercase letters are permitted. A hexadecimal integer literal is always interpreted as a positive integer.


Both numeric and hexadecimal integer literals produce the same integer type with the same set of member methods.

See the Math chapter for more information on the integer type.

Decimal Literals

A decimal is a fractional number. Decimal numbers contain a decimal point and therefore are called “decimals”. Lasso supports 64-bit decimals. This gives Lasso’s decimal numbers a range from approximately negative to positive 2x10^300 and with precision down to 2x10^-300. A decimal literal begins with an optional “-” or “+” character followed by zero or more digits, a decimal point, one or more additional digits, and ending with an optional exponent. A decimal exponent begins with an upper or lowercase “E”, followed by an optional “-” or “+” character followed by one or more digits. Lasso also supports decimal literals for NaN (not a number) as well and positive and negative infinity. (Note that case is irrelevant when using the NaN and infinity literals.)


See the Math chapter for more information on the decimal type.

Tag Literals

A tag is an object that uniquely represents a particular string of characters. Unlike strings, tags cannot be modified. Tags are used to represent type and method names as well as variable names. A tag should begin with a letter or underscore, followed by zero or more letters, numbers, underscores, or period characters. Tags cannot contain spaces.

Tags are commonly used when applying type constraints to methods, data members, and variables; though they have other purposes as well, such as type and object introspection.

A tag literal consists of two colons followed by the tag’s characters.

// Creates a tag object representing "name"

In Lasso, the tag type is used in many different locations. For example, when asking an object what type it is with type, it will reply with a tag object representing its name. Since there will be only one tag object for every individual name, comparing tags for equality is very fast.


Checks if a tag matching the given string value exists without attempting to create a tag. Returns the tag if it exists or “void” if it does not.

Staticarray Literals

Lasso’s staticarray type is an efficient, non-resizable collection for holding any series of object types which is used in many places in Lasso. Staticarrays are created in the same way as any object, but Lasso supports a shortcut syntax to produce staticarrays. This expression begins with an open parenthesis immediately followed by a colon, then zero or more comma-delimited expressions, ending with the closing parenthesis.

// Creates a staticarray containing 1, 2, and "hello"
(: 1, 2, 'hello')

See the Collections chapter for more information on the staticarray type.

Series Literals

Lasso’s generateSeries type is a quick and efficient way to create a series or range of integers for use with query expressions. The shortcut syntax for creating a series consists of a starting integer and ending integer separated by the word “to”. An optional integer specifying the step size, which defaults to 1, can be added after the word “by”.

0 to 10 by 2
// => 0, 2, 4, 6, 8, 10

See the Query Expressions chapter for more information on the generateSeries type.

Null and Void

type null

A null represents a blank or empty value, indicated in code by the word null. All types inherit from null , so its member methods (listed under Type/Object Introspection Methods in the Types chapter) can be used by any type.

type void

A type indicated in code by void which is similar to null in that it is only ever equal to itself, but indicates a non-existent rather than an empty value.


Lasso supports three types of comments: single line comments, block comments, and doc comments. Single line and block comments are ignored, having no effect on the execution of any nearby code. Doc comments are saved with the adjacent method, type, or trait, as explained below.

Single Line Comments

A single line comment begins with two forward slashes (//). The comment runs until the end of the line, which is either a carriage return, line feed, or a carriage return/line feed pair.

local(n) = 123 // This is the first comment
// This is another comment
#n += 456

Note that when embedding Lasso code between a set of delimiters, a closing delimiter on the same line as a single line comment will be skipped by the Lasso parser.

Block Comments

A block comment permits a large section of code to be commented. Any characters, as well as multiple lines, are permitted between the opening delimiter (/*) and closing delimiter (*/). Block comments cannot be nested.

local(n) = 123
/* this is a block comment
it has multiple lines */
#n += 456

Doc Comments

A doc comment permits a block of documentation to be associated with either a type, trait, or method. This comment is not processed by Lasso in any way, but is saved as-is with the object. A doc comment begins with the opening doc comment delimiter (/**!) and runs until a closing delimiter (*/). Any characters can appear within a doc comment, and a doc comment can consist of multiple lines.

Doc comments can only appear in the following locations:

  • Immediately before a type definition
  • Immediately before a trait definition
  • Immediately before a member or unbound method definition
  • Immediately before a trait’s provide or require section
    This doc comment is associated with this method
define foo->xyz() => { ... }

    This doc comment is associated with this type definition
define foo => type {
       Doc comment for the type's xyz() method
   public xyz() => { ... }

    This doc comment is associated with this trait
define tBar => trait {
       Doc comment for the trait's doIt() method
   provide doIt() => { ... }

Doc comments for a type can be set and retrieved programatically using the tag->docComment method, as long as Lasso is run with the LASSO9_RETAIN_COMMENTS variable enabled.

$> env LASSO9_RETAIN_COMMENTS=1 lasso9 -s "::array->docComment"
An array is an object that can hold multiple values…

$> env LASSO9_RETAIN_COMMENTS=1 lasso9 -s "
::boolean->docComment = 'Boolean objects are either true or false.'
Boolean objects are either true or false.