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expanding macro examples, trying to adhere to style guidelines

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Brad Smith 2017-05-23 17:07:45 -04:00
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doc/ca65.sgml
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@ -4286,7 +4286,8 @@ different:
The common practice of wrapping C macros in parentheses may cause
unintended problems here, such as accidentally implying an
indirect addressing mode. While the definition of a macro requires
parentheses around its argument list, when invoked they should not be included.
parentheses around its argument list, when invoked they should not be
included.
</itemize>
@ -4320,18 +4321,44 @@ Macros with parameters may also be useful:
DEBUG "Assembling include file #3"
</verb></tscreen>
Note that, while formal parameters have to be placed in braces,
the actual parameters used when invoking the macro should not use braces.
The invoked parameters are separated by commas only, if parentheses are
used by accident they will become part of the replaced token:
Note that, while formal parameters have to be placed in parentheses,
the actual argument used when invoking the macro should not be.
The invoked arguments are separated by commas only, if parentheses are
used by accident they will become part of the replaced token.
If you wish to have an expression follow the macro invocation, the
last parameter can be enclosed in curly braces {} to indicate the end of that
argument.
Examples:
<tscreen><verb>
.define COMBINE(ta,tb,tc) ta+tb*10+tc*100
COMBINE 5,6,7 ; 5+6*10+7*100 = 765 correct
COMBINE(5,6,7) ; (5+6*10+7)*100 = 7200 incorrect!
.word COMBINE 5,6,7 ; 5+6*10+7*100 = 765
.word COMBINE(5,6,7) ; (5+6*10+7)*100 = 7200 ; incorrect use of parentheses
.word COMBINE 5,6,7+1 ; 5+6*10+7+1*100 = 172
.word COMBINE 5,6,{7}+1 ; 5+6*10+7*100+1 = 766 ; {} encloses the argument
.word COMBINE 5,6-2,7 ; 5+6-2*10+7*100 = 691
.word COMBINE 5,(6-2),7 ; 5+(6-2)*10+7*100 = 745
.word COMBINE 5,6,7+COMBINE 0,1,2 ; 5+6*10+7+0+1*10+2*100*100 = 20082
.word COMBINE 5,6,{7}+COMBINE 0,1,2 ; 5+6*10+7*100+0+1*10+2*100 = 975
</verb></tscreen>
With C macros it is common to enclose the results in parentheses to
prevent unintended interactions with the text of the arguments, but
additional care must be taken in this assembly context where parentheses
may alter the meaning of a statement. In particular, indirect addressing modes
may be accidentally implied:
<tscreen><verb>
.define DUO(ta,tb) (ta+(tb*10))
lda DUO(5,4), Y ; LDA (indirect), Y
lda 0+DUO(5,4), Y ; LDA absolute indexed, Y
</verb></tscreen>
<sect1>Characters in macros<p>
When using the <ref id="option-t" name="-t"> option, characters are translated