Embedded Commands and Initialization Files

This section discusses some differences that exist between compiling a file into QOF with qpc and compiling that file into memory using compile/1 under the Development System. In certain cases, if an application program was developed interactively using the built-in compiler, some changes may have to be made to the code before using qpc to compile it and link it with the Development Kernel or Runtime Kernel.

For example, if a file containing the following is compiled into memory, the embedded command will succeed after writing an x and a newline to the current output stream. 

     f(x).
     f(z).
     
     :- f(X), write(X), nl.

Whereas, if the same file is given to qpc, a warning will be printed indicating that the embedded command failed. The reason for this is that when qpc compiles a Prolog file, it reads clauses from the source file one after the other and compiles them into a QOF file. The clauses for f/1 are not kept in memory, and the attempt to access them fails.

You do not need to read this section if both of the following are true.

  1. The only embedded commands that you use in your Prolog files are commands to load other files, that is, commands from the list at the beginning of sap-srs-dep.
  2. You do not use term_expansion/2 to transform your source code at compile-time.