Execution modes

There are two execution modes: usual mode and debugging mode. The query

      trace

switches the execution mode to the debugging mode, and the query

      notrace

switches the execution mode back to the usual mode. In debugging mode, the execution of asserted and consulted clauses can be traced. Compiled code can also be traced if the code is generated when the Prolog flag compiling has the value debugcode.

To trace part of the execution of a program, use spy to set spy points.

      spy(Atom/Arity).

The spy points can be removed by

      nospy

To remove only one spy point, use

      nospy(Atom/Arity)