Pascal Preprocessor

A

This appendix describes the preprocessors, cpp(1) and cppas.

`cpp`-

cpp(1) is the C language preprocessor. Pascal runs your source program through cpp(1) when you compile it without the -xl option. For a complete description of cpp(1), see the Solaris documentation.

`cppas`-

The cppas preprocessor handles the Pascal conditional variables and compiler directives. You call cppas using the -xl option.

Conditional Variables

A conditional variable is defined when it appears in a %var directive; otherwise, it is undefined. In addition, we predefine:

__sun

__SVR4

sparc

__sparc

__SUNPRO_PC=0x400

unix

__unix

sun

`__sun`	`__SVR4`	`sparc`
`__sparc`	`__SUNPRO_PC=0x400`	`unix`
`__unix`	`sun`

These variables are not predefined when you use -s0, -s1, -V0, or -V1.

A defined conditional variable is enabled (true) when it appears in either the %enable directive or in the -config option; otherwise, it is disabled (false), as in:





%var one two



%enable two

%var one two %enable two

The following section describes %var and %enable. Programs that contain conditional variables must be compiled with the -xl option.

Compiler Directives

A directive indicates some action for the compiler to take. You can use a directive anywhere in your program.

Each directive consists of a percent sign (%) followed by the directive name. Programs that contain compiler directives must be compiled with the -xl option.

Table A-1 summarizes the compiler directives.

Table A-1 cppas Compiler Directives

Compiler Directive
Description

%config

Sets a special predefined conditional variable with a value of either true or false.

%debug

Instructs pc to compile this line of code when you use the -cond compiler directive.

%else

If expression in %if expression %then is false, the compiler skips over the %then part and executes the %else part instead.

%elseif

If expression in %if expression %then is false, the compiler skips over the %then part and executes the %elseif part instead. Similar to %else.

%elseifdef

If expression in %ifdef expression %then is false, the compiler skips over the %then part and executes the %elseifdef part instead.

%enable

Sets a conditional variable to true.

%endif

Indicates the end of an %if or %ifdef directive.

%error

Prints a string on the standard output and treats it as an error.

%exit

Stops processing the current Pascal source file.

%if

When the compiler encounters a %if expression %then directive, it evaluates expression. If expression is true, pc executes the statements after %then. If expression is false, pc skips over %then.

%ifdef

Determines whether or not you previously defined a conditional variable in a %var directive.

%include

Inserts the lines from the specified file into the input stream.

%list

Enables a listing of the program.

%nolist

Disables the program listing.

%slibrary

Inserts the lines from the specified file into the input stream. Same as %include.

%var

Defines conditional variables.

%warning

Prints a warning string on the standard output.

Table A-1 `cppas` Compiler Directives
Compiler Directive	Description
`%config`	Sets a special predefined conditional variable with a value of either `true` or `false`.
`%debug`	Instructs pc to compile this line of code when you use the -cond compiler directive.
`%else`	If expression in %if expression %then is `false`, the compiler skips over the %then part and executes the %else part instead.
`%elseif`	If expression in %if expression %then is `false`, the compiler skips over the %then part and executes the %elseif part instead. Similar to %else.
`%elseifdef`	If expression in %ifdef expression %then is false, the compiler skips over the %then part and executes the %elseifdef part instead.
`%enable`	Sets a conditional variable to `true`.
`%endif`	Indicates the end of an %if or %ifdef directive.
`%error`	Prints a string on the standard output and treats it as an error.
`%exit`	Stops processing the current Pascal source file.
`%if`	When the compiler encounters a %if expression %then directive, it evaluates expression. If expression is `true`, `pc` executes the statements after %then. If expression is `false`, `pc` skips over %then.
`%ifdef`	Determines whether or not you previously defined a conditional variable in a %var directive.
`%include`	Inserts the lines from the specified file into the input stream.
`%list`	Enables a listing of the program.
`%nolist`	Disables the program listing.
`%slibrary`	Inserts the lines from the specified file into the input stream. Same as %include.
`%var`	Defines conditional variables.
`%warning`	Prints a warning string on the standard output.

The rest of this appendix contains detailed descriptions and examples of each directive.

Example





The Pascal program, config.p, which defines the conditional variables one and two


program config_example(output);






{ This program demonstrates the use of the



  %config compiler directive. }






var 



    a: integer := maxint;



    b: integer := minint;






%var one two 






begin



    writeln('Begin program.');



    %if one %then



        writeln('One is defined as ', a:2, '.');



    %elseif two %then



        writeln('Two is defined as ', b:2, '.');



    %elseif %config %then



        writeln('Nothing is defined.');



    %endif



    writeln('End program.')



end. { config_example }

The Pascal program, config.p, which defines the conditional variables one and two	program config_example(output); { This program demonstrates the use of the %config compiler directive. } var a: integer := maxint; b: integer := minint; %var one two begin writeln('Begin program.'); %if one %then writeln('One is defined as ', a:2, '.'); %elseif two %then writeln('Two is defined as ', b:2, '.'); %elseif %config %then writeln('Nothing is defined.'); %endif writeln('End program.') end. { config_example }

The output when you compile config.p without the-config option

hostname% pc -xl config.p

hostname% a.out

Begin program.

End program.

The output when you compile config.p without the`-`config option	hostname% pc -xl config.p hostname% a.out Begin program. End program.

The output when you define the variable one

hostname% pc -xl -config one config.p

hostname% a.out

Begin program.

One is defined as 32767.

End program.

The output when you define the variable `one`	hostname% pc -xl -config one config.p hostname% a.out Begin program. One is defined as 32767. End program.

The output when you define two

hostname% pc -xl -config two config.p

hostname% a.out

Begin program.

Two is defined as -32768.

End program.

The output when you define `two`	hostname% pc -xl -config two config.p hostname% a.out Begin program. Two is defined as -32768. End program.

The output when you define foo

hostname% pc -xl -config foo config.p

Fri Mar 3 15:22 1995 config.p

Error: -CONFIG command argument foo was never declared.

Compilation failed

The output when you define foo	hostname% pc -xl -config foo config.p Fri Mar 3 15:22 1995 config.p Error: -CONFIG command argument foo was never declared. Compilation failed

The `%debug` Directive

The %debug directive instructs pc to compile this line of code when you use the -cond compiler directive.

Syntax

%debug;

Comments

The %debug directive works in conjunction with the -cond compiler option.
-cond causes pc to compile the lines in your program that begin with %debug. Without -cond, pc treats lines with %debug as comments.

Example





The Pascal program, debug.p


program debug_example(output);






{ This program demonstrates the use of the



  %debug compiler directive. }






begin



    writeln ('Hello, how are you?');



    %debug;  writeln ('Fine, thank you.');



end. { debug example }

The Pascal program, debug.p	program debug_example(output); { This program demonstrates the use of the %debug compiler directive. } begin writeln ('Hello, how are you?'); %debug; writeln ('Fine, thank you.'); end. { debug example }

The output when you compile debug.p without the -cond option

hostname% pc -xl debug.p

hostname% a.out

Hello, how are you?

The output when you compile debug.p without the -cond option	hostname% pc -xl debug.p hostname% a.out Hello, how are you?

The output when you use -cond

hostname% pc -xl -cond debug.p

hostname% a.out

Hello, how are you?

Fine, thank you.

The output when you use `-cond`	hostname% pc -xl -cond debug.p hostname% a.out Hello, how are you? Fine, thank you.

The `%else` Directive

The %else directive provides an alternative action to the %if directive.

Syntax

%if expression %then
.
.
%else
.
.
%endif

Example





The Pascal  program, if_then_else.p


program if_then_else (output);



%var red



begin



%if red %then



	writeln ('It is red.');



%else



	writeln ('It is not red.')



%endif



end.

The Pascal program, if_then_else.p	program if_then_else (output); %var red begin %if red %then writeln ('It is red.'); %else writeln ('It is not red.') %endif end.

The output when you compile if_then_else.p without the
-config

hostname% pc -xl if_then_else.p

hostname% a.out

It is not red.

The output when you compile if_then_else.p without the -config	hostname% pc -xl if_then_else.p hostname% a.out It is not red.

The output when you supply
-config with the argument red

hostname% pc -xl -config red if_then_else.p

hostname% a.out

It is red.

The output when you supply -config with the argument red	hostname% pc -xl -config red if_then_else.p hostname% a.out It is red.

The `%elseif` Directive

The %elseif directive provides an alternative action to the %if directive.

Syntax

%if expression %then
.
.
%elseif expression %then
.
.
%endif

Comments

If the expression in %if expression %then is false, pc skips over the %then part and executes the %elseif part instead. expression consists of a conditional variable and the optional boolean operators, and, or, and not. See the %else listing for examples of expression.

Example





The Pascal program, elseif.p


program elseif_example(output);






{ This program demonstrates the use of the



   %if, %then, and %elseif directives. }






%var blue red






begin



    %if blue %then



        writeln('The color is blue.');



    %elseif red %then



        writeln('The color is red.');



    %endif



end. { elseif_example }

The Pascal program, elseif.p	program elseif_example(output); { This program demonstrates the use of the %if, %then, and %elseif directives. } %var blue red begin %if blue %then writeln('The color is blue.'); %elseif red %then writeln('The color is red.'); %endif end. { elseif_example }

The output when you supply
-config with the argument blue

hostname% pc -xl -config blue elseif.p

hostname% a.out

The color is blue.

The output when you supply -config with the argument blue	hostname% pc -xl -config blue elseif.p hostname% a.out The color is blue.

The output when you supply
-config with the argument red

hostname% pc -xl -config red elseif.p

hostname% a.out

The color is red.

The output when you supply -config with the argument red	hostname% pc -xl -config red elseif.p hostname% a.out The color is red.

The `%elseifdef` Directive

The %elseifdef directive provides an alternative action to the %ifdef directive.

Syntax

%ifdef expression %then
.
.
%elseifdef expression %then
.
.
%endif

Comments

If the expression in %ifdef expression %then is false, pc skips over the %then part and executes the %elseifdef part instead. expression consists of a conditional variable and the optional boolean operators, and, or, and not. See the %else listing for examples of expression.

Example





The Pascal program, ifdef.p, which first checks if bird1 has been defined.  If not, it defines it with a %var directive.  If bird1 has been defined, the program checks whether or not it needs to define bird2.


program ifdef_example(output);






%include 'bird.h';






begin



    %ifdef not(bird1) %then



          %var bird1



    %elseifdef not(bird2) %then



          %var bird2



    %endif;






    %if bird1 %then



        writeln('Bird one is a ', a, '.');



    %elseif bird2 %then



        writeln('Bird two is a ', b, '.')



    %endif



end.  { ifdef_example }

The Pascal program, ifdef.p, which first checks if bird1 has been defined. If not, it defines it with a %var directive. If bird1 has been defined, the program checks whether or not it needs to define bird2.	program ifdef_example(output); %include 'bird.h'; begin %ifdef not(bird1) %then %var bird1 %elseifdef not(bird2) %then %var bird2 %endif; %if bird1 %then writeln('Bird one is a ', a, '.'); %elseif bird2 %then writeln('Bird two is a ', b, '.') %endif end. { ifdef_example }





The include file, bird.h


var



    a: array[1..7] of char := 'penguin';



    b: array[1..6] of char := 'toucan';






%var bird1

The include file, bird.h	var a: array[1..7] of char := 'penguin'; b: array[1..6] of char := 'toucan'; %var bird1

The output when you enable bird1 with the -config option

hostname% pc -xl -config bird1 ifdef.p

hostname% a.out

Bird two is a penguin.

The output when you enable bird1 with the -config option	hostname% pc -xl -config bird1 ifdef.p hostname% a.out Bird two is a penguin.

The output when you enable bird2 with the -config option

hostname% pc -xl -config bird2 ifdef.p

hostname% a.out

Bird two is a toucan.

The output when you enable bird2 with the -config option	hostname% pc -xl -config bird2 ifdef.p hostname% a.out Bird two is a toucan.

The `%enable` Directive

The %enable directive sets a conditional variable to true.

Syntax

%enable var1 ..., varN

Comments

A defined conditional variable is enable (true) when it appears in either the %enable directive or in the -config option. Conditional variables are false by default.

Example





The Pascal program, enable.p.  This example sets the conditional variable two to true, which is equivalent to setting the -config option to two on the command-line.


program enable_example(output);






{ This program demonstrates the use of



   the %enable compiler directive. }






var 



    a: integer;



    b: integer;






%var one, two



%enable two






begin



    %if one %then



        a := maxint;



        writeln('One is defined as ', a:2, '.');



    %endif



    %if two %then



        b := minint;



        writeln('Two is defined as ', b:2, '.');



    %endif



end. { enable_example }

The Pascal program, enable.p. This example sets the conditional variable two to `true`, which is equivalent to setting the -config option to two on the command-line.	program enable_example(output); { This program demonstrates the use of the %enable compiler directive. } var a: integer; b: integer; %var one, two %enable two begin %if one %then a := maxint; writeln('One is defined as ', a:2, '.'); %endif %if two %then b := minint; writeln('Two is defined as ', b:2, '.'); %endif end. { enable_example }

The commands to compile and output enable.p

hostname% pc -xl enable.p

hostname% a.out

Two is defined as -32768.

The commands to compile and output enable.p	hostname% pc -xl enable.p hostname% a.out Two is defined as -32768.

The `%endif` Directive

The %endif directive indicates the end of a %if or %ifdef directive. See the sections on %if and %ifdef for more information on this directive.

The `%error` Directive

The %error directive causes the compiler to print a string on the standard output and treat it as an error.

Syntax

%error 'string'

Comments

pc does not produce an object file.

Example





The Pascal program, error.p


program error_example(output);






{ This program demonstrates the use of the



  %error compiler directive. }






%var arch






begin



    %if arch %then



        writeln('This is a SPARC computer.');



    %else



        %error 'Unknown architecture.'



    %endif



end. { error_example }

The Pascal program, error.p	program error_example(output); { This program demonstrates the use of the %error compiler directive. } %var arch begin %if arch %then writeln('This is a SPARC computer.'); %else %error 'Unknown architecture.' %endif end. { error_example }

error.p produces this error if you compile it without the
-config sparc option.

hostname% pc -xl error.p

Tue Feb 28 17:10 1995 error.p

Line 12 : %error 'Unknown architecture.'

E --------------------^---'Unknown architecture.'

Compilation failed

error.p produces this error if you compile it without the `-config sparc` option.	hostname% pc -xl error.p Tue Feb 28 17:10 1995 error.p Line 12 : %error 'Unknown architecture.' E --------------------^---'Unknown architecture.' Compilation failed

The `%exit` Directive

The %exit directive instructs the compiler to stop processing the current Pascal source file.

Syntax

%exit

Comments

If the compiler encounters an %exit directive within an include file, it stops processing the include file, but continues processing the source file in which it is included. In effect, %exit is equivalent to an end-of-file marker.

When the compiler processes an %exit directive within an %if or %ifdef construct, it closes all %if or %ifdefs before it stops processing the current file.

Example





The Pascal program, exit_directive.p


program exit_directive(output);






begin



    writeln('Hello, world!')



end. { exit_directive }



%exit



Everything after the %exit is ignored.



So you can put anything here.

The commands to compile and execute exit_directive.p

hostname% pc -xl exit_directive.p

hostname% a.out

Hello, world!

The `%if` Directive

The %if directive is a conditional branching directive.

Syntax

%if expression %then
.
.
%end if

Comments

When pc encounters a %if directive, it evaluates expression. If expression is true, pc executes the statements in the %then part. If expression is false, pc skips over the %then part and executes the %else, %elseif, or %endif directive. If no such directive exists, pc proceeds to the next statement.

The expression consists of a conditional variable and the optional boolean operators and, or, and not. You can set a conditional variable on the command-line by using the -config option. See "-config" on page 26 for information on this option.

Assuming one and two are conditional variables, expression can be any of the following:

	one

	two

	one and two

	one or two

	not one

	not two

Example

See the example in the %else listing on page 258.

The `%ifdef` Directive

The %ifdef directive determines whether or not you previously defined a conditional variable in a %var directive.

Syntax

%ifdef expression %then
.
.
%elseifdef expression %then
.
.
%endif

Comments

expression consists of a conditional variable and the optional boolean operators and, or, and not. See the %else listing for examples of expression.

%ifdef is especially useful for determining whether or not a conditional variable has been declared in an include file.

Example

See the example in "The %elseifdef Directive."

The `%include` Directive

The %include directive inserts lines from the specified file in the input stream.

Syntax

%include 'filename';

Comments

When cppas encounters the %include directive, it inserts the lines from the file name into the input stream.

Example





The program unit, include_prog.p


program include_prog;






%include 'extern.h';






begin



    global := 1;



    writeln('From MAIN, before PROC: ',global);



    proc;



    writeln('From MAIN,  after PROC: ',global);



end. { include_prog }





The module unit, 


include_mod.p



module include_mod;






define



    global, proc;






%include 'extern.h';






procedure proc; 






begin



    writeln('From PROC             : ',global);



    global := global + 1;



end; { proc }





The include file, include.h


var



    global : integer;






procedure proc; extern;

The commands to compile and execute ext_prog.p and ext_mod.p

hostname% pc -xl include_prog.p include_mod.p

include_prog.p:

include_mod.p:

Linking:

hostname% a.out

From MAIN, before PROC: 1

From PROC : 1

From MAIN, after PROC:2

The `%list` Directive

The %list directive enables a listing of the program.

Syntax

%list;

Comments

The %list directive and the -l compiler option perform the same function.

Example





The Pascal program, list.p


program list_example(output);






{ This program demonstrates the use of the %list



  and %nolist directives. }






%list;



%include 'types.h';



%nolist;






begin



    pri := [red, yellow, blue];



    pos := [true, false];



    cap := ['A'..'Z'];



    dig := [0..100];



	writeln('There are ',	card(pri): 4, '	primary colors.');



	writeln('There are ',	card(pos): 4, '	possibilities.');



	writeln('There are ',	card(cap): 4, '	capital letters.'');



	writeln('There are ',	card(dig): 4, '	digits.')



end. { list_example }





The include file, types.h


type



    lowints = 0..100;



    primary_colors = set of (red, yellow, blue);



    possibilities = set of boolean;



    capital_letters = set of 'A'..'Z';



    digits = set of lowints;






var



    pri: primary_colors;



    pos: possibilities;



    cap: capital_letters;



    dig: digits;

The listing includes the time each unit was compiled and the name of each unit compiled.

hostname% pc -xl list.p

Tue Feb 28 15:48 1995 list.p:

6 %list;

Tue Feb 28 15:50 1995 ./types.h:

1 type

2 lowints = 0..100;

3 primary_colors = set of (red, yellow, blue);

4 possibilities = set of boolean;

5 capital_letters = set of 'A'..'Z';

6 digits = set of lowints;

8 var

9 pri: primary_colors;

10 pos: possibilities;

11 cap: capital_letters;

12 dig: digits;

Tue Feb 28 15:52 1995 list.p:

7 %include 'types.h';

hostname% a.out

There are 3 primary colors

There are 2 possibilities

There are 26 capital letters

There are 101 digits

The `%nolist` Directive

The %nolist directive disables the program listing.

Syntax

%nolist;

Comments

%nolist is the default.

Example

See the example under "The %list Directive."

The `%slibrary` Directive

cppas treats %slibrary in the same manner as the %include directive. See "The %include Directive" on page 267.

The `%var` Directive

The %var directive defines conditional variables for the preprocessor.

Syntax

%var var1 ..., varN

Comments

A conditional variable is defined when it appears in a %var directive; otherwise, it is undefined.

Example

See the example under "The %config Directive" on page 255.

The `%warning` Directive

The %warning directive instructs pc to print a string on the standard output as a compiler warning.

Syntax

%warning 'string'

Comments

pc produces an object file.

Example





The Pascal program, 
warning.p


program warning_example(output);






{ This program demonstrates the use of the



  %warning compiler directives. }






%var blue






begin



    %if blue %then



        writeln('The color is blue.');



    %else



        %warning 'Color not defined'



    %endif



end. { warning_example }

The output when you compile warning.p without the
-config option

hostname% pc -xl warning.p

Fri Mar 3 15:03 1995 warning.p

Line 12: %warning 'Color not defined'

w -------------------^----- 'Architecture not defined'

Pascal Preprocessor

A

cpp-

cppas-

Table A-1 cppas Compiler Directives

The %debug Directive

The %else Directive

The %elseif Directive

The %elseifdef Directive

The %enable Directive

The %endif Directive

The %exit Directive

The %if Directive

Example

The %list Directive

The %nolist Directive

`cpp`-

`cppas`-

Table A-1 `cppas` Compiler Directives

The `%debug` Directive

The `%else` Directive

The `%elseif` Directive

The `%elseifdef` Directive

The `%enable` Directive

The `%endif` Directive

The `%exit` Directive

The `%if` Directive

The `%list` Directive

The `%nolist` Directive