HLASM Language Reference

AIF Instruction
You cannot branch from open code into a macro definition or between macro
definitions, regardless of nested calls to other macro definitions.
The following macro definition generates the statements needed to move a fullword
fixed-point number from one storage area to another. The statements are
generated only if the type attribute of both storage areas is the letter F.
MACRO
&N MOVE &T,&F
AIF (T'&T NE T'&F).END Statement 1
AIF (T'&T NE 'F').END Statement 2
&N ST 2,SAVEAREA Statement 3
L
2,&F
ST
2,&T
L
2,SAVEAREA
.END MEND Statement 4
The logical expression in the operand field of Statement 1 has the value true if the
type attributes of the two macro instruction operands are not equal. If the type
attributes are equal, the expression has the logical value false.
Therefore, if the type attributes are not equal, Statement 4 (the statement named
by the sequence symbol .END) is the next statement processed by the assembler.
If the type attributes are equal, Statement 2 (the next sequential statement) is
processed.
The logical expression in the operand field of Statement 2 has the value true if the
type attribute of the first macro instruction operand is not the letter F. If the type
attribute is the letter F, the expression has the logical value false.
Therefore, if the type attribute is not the letter F, Statement 4 (the statement named
by the sequence symbol .END) is the next statement processed by the assembler.
If the type attribute is the letter F, Statement 3 (the next sequential statement) is
processed.
Extended AIF Instruction
The extended AIF instruction combines several successive AIF statements into one
statement.
►►──┬─────────────────┬──AIF────────────────────────────────────────►
└─sequence_symbol─┘
┌─,─────────────────────────────────┐
►─── ▼ (logical_expression)sequence_symbol┴───────────────────────────►◄
sequence_symbol
is a sequence symbol
logical_expression
is a logical expression the assembler evaluates during conditional assembly
time to determine if it is true or false. If the expression is true (logical value=1),
the statement named by the sequence symbol in the operand field is the next
statement processed by the assembler. If the expression is false (logical
value=0), the next logical expression is evaluated.
Chapter 9. How to Write Conditional Assembly Instructions 391