| Description: Extend wff definition to
include atomic formulas using the equality
     predicate.
 
     (Instead of introducing weq 1517 as an axiomatic statement, as was done in an
     older version of this database, we introduce it by "proving" a
special
     case of set theory's more general wceq 1364.  This lets us avoid overloading
     the = connective, thus preventing ambiguity that
would complicate
     certain Metamath parsers.  However, logically weq 1517 is
considered to be a
     primitive syntax, even though here it is artificially "derived"
from
     wceq 1364.  Note:  To see the proof steps of this
syntax proof, type "show
     proof weq /all" in the Metamath program.)  (Contributed by NM,
     24-Jan-2006.)  |