HLASM Language Reference

How to Specify Macro Definitions
Chapter 7. How to Specify Macro Definitions
A macro definition is a set of statements that defines the name, the format, and the
conditions for generating a sequence of assembler language statements. The
macro definition can then be called by a macro instruction to process the
statements. See page 241 for a description of the macro instruction. To define a
macro you must:
Give it a name
Declare any parameters to be used
Write the statements it contains
Establish its boundaries with a macro definition header statement (MACRO)
and a macro definition trailer statement (MEND)
Except for conditional assembly instructions, this chapter describes all the
statements that can be used to specify macro definitions. Conditional assembly
instructions are described in Chapter 9, “How to Write Conditional Assembly
Instructions” on page 318.
Where to Define a Macro in a Source Module
Macro definitions can appear anywhere in a source module. They remain in effect
for the rest of your source module, or until another macro definition defining a
macro with the same operation code is encountered, or until an OPSYN statement
deletes its definition. Thus, you can redefine a macro at any point in your program.
The new definition is used for all subsequent calls to the macro in the program.
This type of macro definition is called a source macro definition, or, sometimes, an
in-line macro definition. A macro definition can also reside in a system library; this
type of macro is called a library macro definition. Either type can be called from
the source module by the applicable macro instruction.
Macro definitions can also appear inside other macro definitions. There is no limit
to the levels of macro definitions permitted.
The assembler does not process inner macro definitions until it finds the definition
during the processing of a macro instruction calling the outer macro. The following
example shows an inner macro definition:
Example:
MACRO
Macro header for outer macro
OUTER &A,&C= Macro prototype
AIF
('&C' EQ '').A
MACRO
Macro header for inner macro
INNER
Macro prototype
.
.
MEND
Macro trailer for inner macro
.A ANOP
.
MEND
Macro trailer for outer macro
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