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New section covering detection of macro parameter types

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git-svn-id: svn://svn.cc65.org/cc65/trunk@2698 b7a2c559-68d2-44c3-8de9-860c34a00d81
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cuz 2003-11-30 18:22:33 +00:00
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doc/ca65.sgml
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@ -2671,6 +2671,42 @@ parameters:
</verb></tscreen>
<sect1>Detecting parameter types<p>
Sometimes it is nice to write a macro that acts differently depending on the
type of the argument supplied. An example would be a macro that loads a 16 bit
value from either an immediate operand, or from memory. The <tt/<ref
id=".MATCH" name=".MATCH">/ and <tt/<ref id=".XMATCH" name=".XMATCH">/
functions will allow you to do exactly this:
<tscreen><verb>
.macro ldax arg
.if (.match (.left (1, arg), #))
; immediate mode
lda #<(.right (.tcount (arg)-1, arg))
ldx #>(.right (.tcount (arg)-1, arg))
.else
; assume absolute or zero page
lda arg
ldx 1+(arg)
.endif
.endmacro
</verb></tscreen>
Using the <tt/<ref id=".MATCH" name=".MATCH">/ function, the macro is able to
check if its argument begins with a hash mark. If so, two immediate loads are
emitted, Otherwise a load from an absolute zero page memory location is
assumed. So this macro can be used as
<tscreen><verb>
foo: .word $5678
...
ldax #$1234 ; X=$12, A=$34
...
ldax foo ; X=$56, A=$78
</verb></tscreen>
<sect1>Recursive macros<p>
Macros may be used recursively:
@ -3161,7 +3197,7 @@ notice that other than the original TASS, ca65 can never move the
programmcounter backwards - think of it as if you are assembling to disc with
TASS.
<item>Conditional assembly (<tt/.ifeq//<tt/.endif//<tt/.gogo/ etc.) must be
<item>Conditional assembly (<tt/.ifeq//<tt/.endif//<tt/.goto/ etc.) must be
rewritten to match ca65 syntax. Most importantly notice that due to the lack
of <tt/.goto/, everything involving loops must be replaced by
<tt><ref id=".REPEAT" name=".REPEAT"></tt>.