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The main primitive data types in Whiley are:

  • Booleans are denoted by the type bool. This is the simplest of the primitive data types, and has only two possible values: true or false.
  • Integers are denoted by the type int. Integers in Whiley are unbounded. This means that, in theory at least, a variable of type int can take on any possible integer value; this differs from languages like Java, which imposed range limits based on the underlying number presentation (typically 32-bit two’s complement).
  • Reals are denoted by the type real. Reals in Whiley are unbounded rationals. This means that, in theory at least, a variable of type real can take on any possible rational value; again, this offers significantly better precision than, for example, float or double numbers in Java (which uses IEEE 754).

The following simple Whiley program illustrates these data types in action:

void ::main(System.Console console):
    i = 123456789101112131415161718
    r = 1234567.192849103954720300939

This program behaves as expected: by printing out the numbers exactly as shown. Observe that neither of these numbers can be stored in a Java variable of type float or double without losing precision.

Finally, since we have unbound rationals, it is always valid to assign a variable of type int to one of type real and, furthermore, Whiley guarantees there will be no loss of precision. Again, this differs from Java where such assignments may result in a loss of precision (e.g. assigning Java int to float).