User manual

236
mikoBasic PRO for dsPIC30/33 and PIC24
MikroElektronika
Directives #DEFINE and #UNDEFINE
Use directive #DEFINE to dene a conditional compiler constant (“ag”). You can use any identier for a ag, with no
limitations. No conicts with program identiers are possible because the ags have a separate name space. Only one
ag can be set per directive.
For example:
#DEFINE extended_format
Use #UNDEFINE to undene (“clear”) previously dened ag.
Directives #IFDEF, #IFNDEF, #ELSE and #ENDIF
Conditional compilation is carried out by the #IFDEF and #IFNDEF directives. #IFDEF tests whether a ag is currently
dened, and #IFNDEF if the ag is not dened; i.e. whether a previous #DEFINE directive has been processed for that
ag and is still in force.
Directives #IFDEF and #IFNDEF are terminated with the #ENDIF directive and can have an optional #ELSE clause:
#IFDEF ag THEN
block of code
[ #ELSE
alternate block of code ]
#ENDIF
First, #IFDEF checks if ag is dened by means of #DEFINE. If so, only block of code will be compiled. Otherwise,
alternate block of code in #ELSE (if any) will be compiled. #ENDIF ends the conditional sequence. The result of the
preceding scenario is that only one section of code (possibly empty) is passed on for further processing. The processed
section can contain further conditional clauses, nested to any depth; each #IFDEF must be matched with a closing
#ENDIF.
Here is an example:
‘ Uncomment the appropriate ag for your application:
‘#DEFINE resolution10
‘#DEFINE resolution12
#IFDEF resolution10 THEN
// <code specic to 10-bit resolution>
#ELSE
#IFDEF resolution12 THEN
// <code specic to 12-bit resolution>
#ELSE
// <default code>
#ENDIF
#ENDIF
Unlike #IFDEF, #IFNDEF checks if ag is not dened by means of #DEFINE, thus producing the opposite results.