Mikroelektronika MIKROE-724 データシート

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mikoBasic PRO for dsPIC30/33 and PIC24

MikroElektronika

Directives #DEFINE and #UNDEFINE

Use directive

#DEFINE

to define a conditional compiler constant (“flag”). You can use any identifier for a flag, with no

limitations. No conflicts with program identifiers are possible because the flags have a separate name space. Only one

flag can be set per directive.

For example:

#DEFINE extended_format

Use

#UNDEFINE

to undefine (“clear”) previously defined flag.

Directives #IFDEF, #IFNDEF, #ELSE and #ENDIF

Conditional compilation is carried out by the

#IFDEF

and

#IFNDEF

directives.

#IFDEF

tests whether a flag is currently

defined, and

#IFNDEF

if the flag is not defined; i.e. whether a previous

#DEFINE

directive has been processed for that

flag and is still in force.

Directives

#IFDEF

and

#IFNDEF

are terminated with the

#ENDIF

directive and can have an optional

#ELSE

clause:

#IFDEF flag THEN

block of code

[ #ELSE

alternate block of code ]

#ENDIF

First,

#IFDEF

checks if

flag

is defined 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 flag for your application:

‘#DEFINE resolution10

‘#DEFINE resolution12

#IFDEF resolution10 THEN

// <code specific to 10-bit resolution>

#ELSE

#IFDEF resolution12 THEN

// <code specific to 12-bit resolution>

#ELSE

// <default code>

#ENDIF

Unlike

#IFDEF, #IFNDEF

checks if

flag

is not defined by means of

#DEFINE

, thus producing the opposite results.