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pragma(+Option)

Enable or disable compilation or other source processing options.
Option
An atom.

Description

The pragma/1 directive allows to control various compiler options, or other source processing options. A pragma can only be used as a directive in source files or lists given to compile_term/1,2. The effect of a pragma is local to a source file (unlike set_flag/2). Settings are in effect until the next pragma that overrides it or until the end of the file. 
    Option     Effect
   ---------------------------------------------------------------
    [no]debug        generate debuggable code
    [no]expand       do goal expansion/inline compilation
    opt_level(N)     set optimizer level (N>=0)
    [no]skip         set the skipped flag for all compiled predicates
    system           set the type of all compiled predicates to 'built_in'
    [no]warnings     generate compiler warnings
The default for debug/nodebug depends on the global flag debug_compile and the debug compiler option. The default for expand/noexpand depends on the global flag goal_expansion and the expand_goals compiler option. The default for opt_level depends on the opt_level compiler option. The default for skip is off. The default for warnings is on. The global flags are set with set_flag/2 and tested with get_flag/2.

Pragmas which the compiler does not recognise are silently ignored by the compiler, but are recorded and can be retrieved using current_pragma/1. Such pragmas can be atoms or structures with arbitrary arguments.

Modes and Determinism

Exceptions

(148) bad pragma
An unknown Option was given.

Examples

:- pragma(debug).
:- pragma(expand).
twice(X, Y) :-      % this is compiled into debuggable
    Y is 2*X.       % code with expanded arithmetic

See Also

compile / 1, env / 0, get_flag / 2, get_flag / 3, pred / 1, set_flag / 3, set_flag / 2, skipped / 1, unskipped / 1, current_pragma / 1