The simplest expressions are constants. The boolean constants are true and false. Integer constants are unsigned strings of digits such as 0, 123, and 007. String constants are sequences of characters enclosed in double quotes, such as "This is a string." String constants may be at most 1024 characters long. There are other restrictions on strings; see Section 10.
The constants belong to the basic classes Bool, Int, and String. The value of a constant is an object of the appropriate basic class.