macro's name. Use the @code{!POSITIONAL} keyword to declare a
positional argument.
-When a macro is called, every positional argument must be given a
-value in the same order as the defintion.
+When a macro is called, the positional argument values appear in the
+same order as their definitions, before any keyword argument values.
References to a positional argument in a macro body are numbered:
@code{!1} is the first positional argument, @code{!2} the second, and
@item
A @dfn{keyword} argument has a name. In the macro call, its value is
specified with the syntax @code{@i{name}=@i{value}}. The names allow
-keyword argument values to take any order in the call, and even to be
-omitted. When one is omitted, a default value is used: either the
-value specified in @code{!DEFAULT(@i{value})}, or an empty value
-otherwise.
+keyword argument values to take any order in the call.
In declaration and calls, a keyword argument's name may not begin with
@samp{!}, but references to it in the macro body do start with a
If a macro has both positional and keyword arguments, then the
positional arguments must come first in the DEFINE command, and their
-values also come first in macro calls.
+values also come first in macro calls. A keyword argument may be
+omitted by leaving its keyword out of the call, and a positional
+argument may be omitted by putting a command terminator where it would
+appear. (The latter case also omits any following positional
+arguments and all keyword arguments, if there are any.) When an
+argument is omitted, a default value is used: either the value
+specified in @code{!DEFAULT(@i{value})}, or an empty value otherwise.
Each argument declaration specifies the form of its value:
e.g.@: @code{!LENGTH(!EVAL(!vars))} or @code{!LENGTH(!EVAL(!1))}.
@xref{Macro Functions}, for details.
-These rules apply to macro calls, not to uses of macro functions and
-macro arguments within a macro body, which are always expanded.
+These rules apply to macro calls, not to uses within a macro body of
+macro functions, macro arguments, and macro variables created by
+@code{!DO} or @code{!LET}, which are always expanded.
@node Macro Functions
@subsection Macro Functions
@deffn {Macro Function} !NULL
Expands to an empty character sequence.
+@c Keep these examples in sync with the test for !NULL in
+@c tests/language/control/define.at:
@example
!NULL @expansion{} @r{empty}
!QUOTE(!NULL) @expansion{} ''
quote marks reduced to singletons. If the argument was not a quoted
string, @code{!UNQUOTE} expands to the argument unchanged.
+@c Keep these examples in sync with the test for !QUOTE and !UNQUOTE in
+@c tests/language/control/define.at:
@example
!QUOTE(123.0) @expansion{} '123.0'
!QUOTE( 123 ) @expansion{} '123'
@node Macro Notes
@subsection Additional Notes
+@subsubsection Calling Macros from Macros
+
+If the body of macro A includes a call to macro B, the call can use
+macro arguments (including @code{!*}) and macro variables as part of
+arguments to B. For @code{!TOKENS} arguments, the argument or
+variable name counts as one token regardless of the number that
+expands into, for @code{!CHAREND} and @code{!ENCLOSE} arguments the
+delimiters come only from the call, not the expansions, and
+@code{!CMDEND} ends at the calling command, not any end of command
+within an argument or variable.
+
+Macro functions are not supported as part of the arguments in a macro
+call. To get the same effect, use @code{!LET} to define a macro
+variable, then pass the macro variable to the macro.
+
+When macro A calls macro B, the order of their @code{DEFINE} commands
+doesn't matter, as long as macro B has been defined when A is called.
+
@subsubsection Command Terminators
Macros and command terminators require care. Macros honor the syntax
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