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nasmdoc: Document macro parameters range

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Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
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Cyrill Gorcunov 2010-06-05 11:24:59 +04:00
parent 2f40375077
commit 640edfd784
1 changed files with 43 additions and 1 deletions
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doc/nasmdoc.src
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@ -1,5 +1,5 @@
\# --------------------------------------------------------------------------
\#
\#
\# Copyright 1996-2010 The NASM Authors - All Rights Reserved
\# See the file AUTHORS included with the NASM distribution for
\# the specific copyright holders.
@ -2558,6 +2558,48 @@ definition.
See \k{sectmac} for a better way to write the above macro.
\S{mlmacrange} \i{Macro Parameters Range}
NASM also allows you to expand parameters via special construction \c{%\{x:y\}}
where \c{x} is the first parameter index and \c{y} is the last. Any index can
be either negative or positive. Though the indices must never be zero.
For example
\c %macro mpar 1-*
\c db %{3:5}
\c %endmacro
\c
\c mpar 1,2,3,4,5,6
expands to \c{3,4,5} range.
Even more, the parameters can be reversed so that
\c %macro mpar 1-*
\c db %{5:3}
\c %endmacro
\c
\c mpar 1,2,3,4,5,6
expands to \c{5,4,3} range.
But even this is not the last. The parameters can be addressed via negative
indices so NASM will count them reversed. The ones who know Python may see
the analogue here.
\c %macro mpar 1-*
\c db %{-1:-3}
\c %endmacro
\c
\c mpar 1,2,3,4,5,6
expands to \c{6,5,4} range.
Note that NASM uses \i{comma} to separate parameters being expanded.
By the way, here is a trick - you might use the index \c{%{-1:-1}} gives
you the \i{last} argument passed to a macro.
\S{mlmacdef} \i{Default Macro Parameters}