HLASM Language Reference

Nesting Macro Instruction Definitions
while the following macro instruction does not:
MAC1 2+2=4 (2+2 is not a valid keyword)
Periods
A period (.) can be used in the value of an operand or sublist entry. It is passed as
a period. However, if it is used immediately after a variable symbol, it becomes a
concatenation character. Two periods are required if one is to be passed as a
character.
Examples:
3.4
&A.1
&A..1
Nesting Macro Instruction Definitions
A nested macro instruction definition is a macro instruction definition you can
specify as a set of model statements in the body of an enclosing macro definition.
This lets you create a macro definition by expanding the outer macro that contains
the nested definition.
Note that all nested inner macro definitions are effectively “black boxes”: there is no
visibility to the outermost macro definition of any variable symbol or sequence
symbol within any of the nested macro definitions. This means that you cannot use
an enclosing macro definition to tailor or parameterize the contents of a nested
inner macro definition.
This lack of parameterization can be overcome in some cases by using the
AINSERT statement. This lets you generate a macro definition from within another
macro generation. A simple example is shown at “Where to Define a Macro in a
Source Module” on page 243. In Figure 83 on page 312, macro
ainsert_test_macro generates the macro mac1 using a combination of AINSERT
and AREAD instructions. The mac1 macro is then called with a list of seven
parameters.
Chapter 8. How to Write Macro Instructions 311