By default, built-in functions are protected--that is, they may not be
redefined by an @m
command. (To do so cavalierly invites many
kinds of weird disasters.) If it is absolutely necessary to redefine a
built-in function, use the command-line option -Tb
(see -Tb).
Many of FWEB's "built-in functions" are in fact ordinary macros
that are implemented in terms of lower-level built-ins. An example is
$POW
(see $POW), which is constructed from the built-in
function $EVAL
(see $EVAL). By default, such macros are also
protected against redefinition; to override, use the option -Tm
(see -Tm).