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Chapter 6. Macro Processing Language |
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Advanced Macro Processing
The MPL definition function associates an identifier with a functional string. The macro may or may not have an associated pattern consisting of parameters and/or delimiters. Optionally present are local symbols.
The syntax for a macro definition is:
%DEFINE (macro_id define_pattern) [LOCAL id_list] (balanced_text)
The define_pattern is a balanced string which is further analyzed by the MPL processor as follows:
define_pattern = { [parm_id] [delimiter_specifier] }
Delimiter_specifier is one of the following:
A string that contains no non-literal id-continuation, logical blank, or at character (‘@’).
@delimiter_id
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The macro call must have a call pattern which corresponds to the macro define |
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pattern. Regardless of the type of delimiter used to define a macro, once it has |
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been defined, only delimiters used in the definition can be used in the macro call. |
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Macros defined with parentheses and commas require parentheses and commas |
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in the macro call. Macros defined with spaces or any other delimiter require that |
delimiter when called. |
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The define pattern may have three kinds of delimiters: implied blank delimiters, |
identifier delimiters and literal delimiters.
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Literal Delimiters
The delimiters used in user-defined macros (parentheses and commas) are literal delimiters. A literal delimiter can be any character except the metacharacter.
When you define a macro using a literal delimiter, you must use exactly that delimiter when you call the macro. If the specified delimiter is not used as it appears in the definition, a macro error occurs.
When defining a macro, the delimiter string must be literalized, if the delimiter meets any of the following conditions:
more than one character,
a macro identifier character (A-Z, 0-9, _, or ?),
a commercial at (@), a space, tab, carriage return, or linefeed.
Use the escape function (%n) or the bracket function (%()) to literalize the delimiter string.
This is the simple form shown earlier:
Before Macro Expansion |
After Macro Expansion |
%*DEFINE(MAC(A,B))(%A %B) |
null string |
%MAC(4,5) |
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In the following example brackets are used instead of parentheses. The |
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commercial at symbol separates parameters: |
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%*DEFINE (MOV[A%(@)B]) (MOV %A,%B) |
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null string |
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%MOV[P0@P1] |
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MOV P0,P1 |
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In the next two examples, delimiters that could be id delimiters have been |
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defined as literal delimiter (the differences are noted): |
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%*DEFINE(ADD (R10 AND B)) (ADD R10,%B) |
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→ |
null string |
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%ADD (R10 AND #27H) |
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ADD R10,#27H |
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Spaces around AND are considered as part of the argument string.
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Chapter 6. Macro Processing Language |
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Blank Delimiters
Blank delimiters are the easiest to use. Blank delimiter is one or more spaces, tabs or new lines (a carriage-return/linefeed pair) in any order. To define a macro that uses the blank delimiter, simply place one or more spaces, tabs, or new lines surrounding the parameter list.
When the macro defined with the blank delimiter is called, each delimiter will match a series of spaces, tabs, or new lines. Each parameter in the call begins with the first non-blank character, and ends when a blank character is found.
Source text
%*DEFINE (X1 X2 X3) (P2=%X2, P3=%X3) %X1 assembler A251
Output text
P2=assembler, P3=A251
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Identifier Delimiters
Identifier delimiters are legal macro identifiers designated as delimiters. To define a macro that uses an identifier delimiter, you must prefix the delimiter with the @ symbol. You must separate the identifier delimiter from the macro identifiers (formal parameters or macro name) by a blank character.
When calling a macro defined with identifier delimiters, a blank delimiter is required to precede the identifier delimiter, but none is required to follow the identifier delimiter.
Source text
%*DEFINE (ADD X1 @TO X2 @STORE X3)(
MOV |
R1,%X1 |
MOV |
R2,%X2 |
ADD |
R1,R2 |
MOV |
%X3,R1 |
) |
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%ADD VAR1 TO VAR2 STORE VAR3
Output text
MOV R1,VAR1
MOV R2,VAR2
ADD R1,R2
MOV VAR3,R1
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