Numbers

A number in the current front-end is either an integer or a floating-point literal. Imaginary suffix forms are intentionally outside the hardened lexer/parser contract for this phase.

Intigers

An integer has one of four forms:

• A decimal literal starts with a decimal digit and continues with decimal digits and optional separating underscores.
• A hex literal starts with 0x or 0X and then uses hex digits with optional separating underscores.
• An octal literal starts with 0o or 0O and then uses octal digits with optional separating underscores.
• A binary literal starts with 0b or 0B and then uses binary digits with optional separating underscores.

var decimal: int = 45;
var hexadec: int = 0x6HF53BD5;
var octal: int = 0o822371;
var binary: int = 0b010010010;

Underscore

Underscore character U+005F (_) is a special character, that does not represent anything withing the number laterals. An integer lateral containing this character is the same as the one without. It is used only as a syntastc sugar:

var aNumber: int = 540_467;
var bNumber: int = 540467;

assert(aNumber, bNumber)

Floating points

A floating-point has one of two forms:

• A decimal literal followed by a period character U+002E (.). This is optionally followed by another decimal literal.
• A decimal literal that follows a period character U+002E (.).
• A decimal literal followed by a period with no fractional digits is also accepted by the current front-end.

var aFloat: flt = 3.4;
var bFloat: flt = .4;
var cFloat: flt = 1.;

Current front-end note

Imaginary literals such as 5i remain a language-design topic in the book, but they are not tokenized or lowered by the current hardened stream/lexer/parser pipeline.