$DEFINE
: Deferred macro definition
$DEFINE
behaves like the FWEB macro command @m
, but
it is intended to appear in the code part, not the definition part (so
it is processed during output, not input). Thus, the code fragment
a = A; $DEFINE(A 1)@% a = A;
tangles to
a= A; a= 1;
(Notice how the @%
command was used to kill an unwanted newline,
analogous to the dnl
macro in m4
.)
In the above example, one could also say $DEFINE(A=1)
.
To define a macro with arguments, say something like
$DEFINE(A(x)x*x)
. Do not say $DEFINE(A(x)=x*x)
, as
in this case the equals sign will be included in the macro expansion.
One must use the equals sign as a means of preventing parentheses from
being interpreted as an argument in examples like
$DEFINE(A=(x))
This expands to (x)
.
A completely equivalent shorthand notation for $DEFINE
is
$M
.