$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.