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Macro Parameters/Substitution Symbols
5-12
5.3.6
Accessing Individual Characters of Subscripted Substitution Symbols
In a macro, you can access the individual characters (substrings) of a substitu-
tion symbol with subscripted substitution symbols. You must use the forced
substitution operator for clarity.
You can access substrings in two ways:
-
:
symbol (well-defined expression):
This method of subscripting evaluates to a character string with one
character.
-
:
symbol (well-defined expression
1
,
well-defined expression
2
):
In this method, expression
1
represents the substring’s starting position,
and expression
2
represents the substring’s length. You can specify
exactly where to begin subscripting and the exact length of the resulting
character string.
The index of substring characters begins with 1, not 0.
Example 5–8 and Example 5–9 show built-in substitution symbol functions
used with subscripted substitution symbols.
Example 5–8. Using Subscripted Substitution Symbols to Redefine an Instruction
ADDX
.macro
ABC
.var
TMP
.asg
:ABC(1):,TMP
.if
$symcmp(TMP,”#”) = 0
ADD
ABC, A
.else
.emsg
”Bad Macro Parameter”
.endif
.endm
ADDX
#100
;macro call
ADDX
*AR1
;macro call
In Example 5–8, subscripted substitution symbols redefine the add instruction
so that it handles short immediates.
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