Literals

Literals

(some literal expressions are also described in data types)

A literal is a way to specify an unnamed constant value corresponding to a given data type. GAML supports various types of literals for often — or less often — used data types.

Table of contents

• Literals
  • Simple Types
  • Literal Constructors
  • Universal Literal

Simple Types

Values of simple (i.e. not composed) types can all be expressed using literal expressions. Namely:

• bool: true and false.
• int: decimal value, such as 100, or hexadecimal value if preceded by '#' (e.g. #AAAAAA, which returns the int 11184810)
• float: the value in plain digits, using '.' for the decimal point (e.g. 123.297)
• string: a sequence of characters enclosed between quotes ('my string') or double quotes ("my string")

Literal Constructors

Although they are not strictly literals in the sense given above, some special constructs (called literal constructors) allow the modeler to declare constants of other data types. They are actually operators but can be thought of literals when used with constant operands.

• pair: the key and the value separated by :: (e.g. 12::'abc')
• list: the elements, separated by commas, enclosed inside square brackets (e.g. [12,15,15])
• map: a list of pairs (e.g. [12::'abc', 13::'def'])
• point: 2 or 3 int or float ordinates enclosed inside curly brackets (e.g. {10.0,10.0,10.0})

Universal Literal

Finally, a special literal, of type unknown, is shared between the data types and all the agent types (aka species). Only bool, int and float, which do not derive from unknown, do not accept this literal. All the others will accept it (e.g. string s <- nil; is ok).

• unknown: nil, which represents the non-initialized (or, literally, unknown) value.