Pragmatic directives: Difference between revisions

=={{header|NetRexx}}==

NetRexx provides three pragma-like instructions: <tt>OPTIONS</tt>, <tt>NUMERIC</tt> and <tt>TRACE</tt>.

* '''<tt>OPTIONS</tt>''' provides the ability to pass special requests to the language processor (i.e. a compiler or interpreter).

:The syntax is:<lang NetRexx>options wordlist;</lang>

:where ''wordlist'' is one or more symbols separated by blanks. The individual words in ''wordlist'' might control optimizations, enforce standards, enable implementation-dependent features, etc.

:The current default settings of <tt>OPTIONS</tt> is:<lang NetRexx>options -

nobinary nocomments nocompact console crossref decimal nodiag noexplicit noformat java logo noreplace nosavelog nosourcedir -

nostrictargs nostrictassign nostrictcase nostrictimport nostrictprops nostrictsignal nosymbols trace2 noutf8 verbose3</lang>

* '''<tt>NUMERIC</tt>''' is used to change the way in which arithmetic operations are carried out by a program.

:The syntax is:<lang NetRexx>numeric digits [exprd];

numeric form [scientific | engineering];</lang>

:*'''<tt>numeric digits</tt>''' controls the precision under which arithmetic operations will be evaluated. The default for ''exprd'' is '''9''' i.e. '''<tt>numeric digits 9</tt>'''.<br />There is normally no limit to the value for <tt>'''numeric digits'''</tt> (except the constraints imposed by the amount of storage and other resources available) but note that high precisions are likely to be expensive in processing time.

:*'''<tt>numeric form</tt>''' controls which form of exponential notation is to be used for the results of operations.

* '''<tt>TRACE</tt>''' is used to control the tracing of the execution of NetRexx methods, and is primarily used for debugging.

:The Syntax is:<lang NetRexx>trace tracesetting

trace var [varlist]</lang>

:where ''tracesetting'' is one of:

:*'''<tt>all</tt>'''

::All clauses (except null clauses without commentary) which are in methods and which are executed after the trace instruction will be traced.

:*'''<tt>methods</tt>'''

::All <tt>method</tt> clauses in the class will be traced when the method they introduce is invoked, together with the values of the arguments passed to each method.

:*'''<tt>off</tt>'''

::turns tracing off.

:*'''<tt>results</tt>'''

::similar to <tt>trace all</tt> for the clauses in a <tt>method</tt> with the addition that the results of all ''expression'' evaluations and any results assigned to a variable by an assignment, <tt>loop</tt>, or <tt>parse</tt> instruction are also traced.

:and ''varlist'' provides a list of variables which will be monitored during execution.