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ABL Reference
ABL Syntax Reference : &IF, &THEN, &ELSEIF, &ELSE, and &ENDIF preprocessor directives
 

&IF, &THEN, &ELSEIF, &ELSE, and &ENDIF preprocessor directives

These directives set logical conditions for the inclusion of blocks of code to compile.

Syntax

&IF expression &THEN
block
[ &ELSEIF expression &THEN
block]...
[ &ELSE
block]
&ENDIF
expression
An expression that can contain preprocessor name references, the operators listed in Table 6, the ABL functions listed in Table 7, and the DEFINED( ) preprocessor function.
When it encounters an &IF directive, the preprocessor evaluates the expression that immediately follows. This expression can continue for more than one line; the &THEN directive indicates the end of the expression. If the expression evaluates to TRUE, then the block of code between it and the next &ELSEIF, &ELSE, or &ENDIF is compiled. If the expression evaluates to FALSE, the block of code is not compiled and the preprocessor proceeds to the next &ELSEIF, &ELSE, or &ENDIF directive. No include files referenced in this block of code are included in the final source. You can nest &IF directives.
The expression that follows the &ELSEIF directive is evaluated only if the &IF expression tests false. If the &ELSEIF expression tests TRUE, the block of code between it and the next &ELSEIF, &ELSE, or &ENDIF directive is compiled. If the &ELSEIF expression tests FALSE, the preprocessor proceeds to the next &ELSEIF, &ELSE, or &ENDIF directive.
The block of code between the &ELSE and &ENDIF directives is compiled only if the &IF expression and the &ELSEIF expressions all test false. If there are no &ELSEIF directives, the block of code is compiled if the &IF expression tests false.
Once any &IF or &ELSEIF expression evaluates to TRUE, no other block of code within the &IF...&ENDIF block is compiled.
The &ENDIF directive indicates the end of the conditional tests and the end of the final block of code to compile.
The following table shows how preprocessor expressions are evaluated.
Table 5. Preprocessor expressions
Type of expression
TRUE
FALSE
LOGICAL
TRUE
FALSE
CHARACTER
non-empty
empty
INTEGER
non-zero
0
INT64
non-zero
0
DECIMAL
not supported
not supported
The following table lists the operators supported within preprocessor expressions. These operators have the same precedence as the regular ABL operators.
Table 6. Preprocessor operators
Operator
Description
+
Addition
-
Subtraction
*
Multiplication
/
Division
=
Equality
<>
Inequality
>
Greater than
<
Less than
=>
Greater than or equal to
<=
Less than or equal to
AND
Logical and
OR
Logical or
NOT
Logical not
BEGINS
Compares the beginning letters of two expressions
MATCHES
Compares two strings
The following table lists the ABL functions supported within preprocessor expressions.
Table 7. Functions allowed in preprocessor expressions
ABSOLUTE
ASC
AUDIT-ENABLED
DATE
DAY
DBTYPE
DECIMAL
ENCODE
ENTRY
ETIME
EXP
FILL
INDEX
INT64
INTEGER
KEYWORD
KEYWORDALL
LC
LEFT-TRIM
LENGTH
LIBRARY
LOG
LOOKUP
MATCHES
MAXIMUM
MEMBER
MINIMUM
MODULO
MONTH
NUM-ENTRIES
OPSYS
PROCESS-ARCHITECTURE
PROPATH
PROVERSION
RANDOM
REPLACE
RIGHT-TRIM
R-INDEX
ROUND
SQRT
STRING
SUBSTITUTE
SUBSTRING
TIME
TODAY
TRIM
TRUNCATE
WEEKDAY
YEAR

Note

When the preprocessor evaluates expressions, all arithmetic operations are performed with integers. Preprocessor name references used in arithmetic operations must evaluate to integers.

See also

&GLOBAL-DEFINE preprocessor directive, &SCOPED-DEFINE preprocessor directive, &UNDEFINE preprocessor directive