HP 3000 Manuals

HP Pascal/iX Reference Manual

IF 

IF is an HP Pascal Option.

The IF compiler option specifies code to be compiled conditionally,
depending on the value of a Boolean expression.

Syntax 

     $IF 'Boolean_expression'$

Parameter 

Boolean_expression  Any constant Boolean expression containing the
                    operators AND, OR, and NOT and parentheses.  The SET
                    compiler option must assign the value TRUE or
                    FALSE to each identifier before it appears in
                    Boolean_expression.  The identifier operands cannot
                    have the spellings of Boolean operators (NOT, AND,
                    OR). The operators are evaluated in the order
                    dictated by HP Pascal operator precedence.

Default       Not applicable.

Location      Anywhere.

The IF option must be used with the SET and ENDIF options, and can be
used with the ELSE option, as follows:

$SET 'identifier = Boolean [{,}identifier = Boolean]'$
                           [{;}                    ]
     $IF Boolean_expression$ 

[source code          ]
[to be compiled       ]
[if Boolean_expression]
[is TRUE              ]
     $ELSE$

[source code          ]
[to be compiled       ]
[if Boolean_expression]
[is FALSE             ]

     $ENDIF$

IF options can be nested; that is, the source code to be compiled
conditionally can contain IF options.  The maximum nesting level is 16.

Because the IF, ENDIF, ELSE, and SET options (together) allow conditional
compilation, several programmers with different needs can use them to
customize a single compilation unit.

Example 1 

The following two program fragments are equivalent:

     {Fragment 1}
     $SET 'group1=true, group2=false'$
        .
        .
        .
     $IF 'group1 AND (NOT group2)'$

[source_line]
[ .         ]
[ .         ]
[ .         ]
     $ENDIF$

     {Fragment 2}
     $SET 'group1 = true'$
     $SET 'group2 = false'$
        .
        .
        .
     $IF 'group1'$
        $IF 'NOT group2'$

 [source_line]
 [ .         ]
 [ .         ]
 [ .         ]
        $ENDIF$
     $ENDIF$

Example 2 

     $SET 'group1=FALSE'$
        .
        .
        .
     $IF 'group1'$

 [source_line]
 [ .         ]
 [ .         ]
 [ .         ]

     $ELSE$

 [source_line]
 [ .         ]
 [ .         ]
 [ .         ]
     $ENDIF$

Example 3 

     $SET 'group3=true,group2=false;group1=false'$
        .
        .
        .
     $IF 'group1'$

 [source_line]
 [ .         ]{group1}
 [ .         ]
 [ .         ]

     $ELSE$
        $IF 'group2'$

 [source_line]
 [ .         ]{group2}
 [ .         ]
 [ .         ]
     $ELSE$
        $IF 'group3'$

 [source_line]
 [ .         ] {group3}
 [ .         ]
 [ .         ]

           $ENDIF$
        $ENDIF$
     $ENDIF$

MPE/iX 5.0 Documentation