9.9.3 Literal

Definition and examples

A literal is "a syntactic representation of the form of the referent". That is, it shows the form of the referent. For example:

   [Number: 18]
   [String: 'abcdefg']
   [Measure: <18, cm>]

The three kinds of literals

There are three kinds of literals:

  1. A number
  2. A string
  3. An encoded literal

All three kinds are exemplified in the above examples. The string is "'abcdefg'", while the encoded literal is "<18, cm>".

Encoded literals

The encoded literal has the following form:

   <literal, string>

where the string designates the unit of the literal. Other examples include:

   [Temperature: <37.5, DegreesCelsius> ]
   "There is a temperature, which is 37.5 degrees Celsius."
   [Number: <12, Rhino>]
   "There is a number, which is 12 rhinos."
   [Measure: <2.54, cm> ]
   "There is a measure, which is 2.54 cm."

Difference between "18" and "@18"

Note how there is a difference between the designator "18" and the quantifier "@18". To illustrate the difference, we show two different concepts:

   [Number: 18]
   "There is a number, which is 18"
   [Number: @18]
   "There are 18 numbers (and we haven't specified what they are)"

The designator "18" tells us what the number is, while the quantifier "@18" tells us how many numbers there are.

To drive home the point, let us show this example:

   [Number: @18 18]
   "There are 18 numbers.  Each of these numbers is the number 18."

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