\DOC new_definition

\TYPE {new_definition : string * term -> thm}

\SYNOPSIS
Declare a new constant and install a definitional axiom in the current theory.

\DESCRIBE
The function {new_definition} provides a facility for definitional
extensions to the current theory.  It takes a pair argument consisting
of the name under which the resulting definition will be saved
in the current theory segment, and a term giving the desired definition.  The
value returned by {new_definition} is a theorem which states the definition
requested by the user.

Let {v_1},...,{v_n} be tuples of distinct variables, containing the
variables {x_1,...,x_m}.  Evaluating
{new_definition (name, c v_1 ... v_n = t)}, where {c} is not
already a constant, declares the sequent {({},\v_1 ... v_n. t)} to
be a definition in the current theory, and declares {c} to be a new
constant in the current theory with this definition as its
specification. This constant specification is returned as a theorem
with the form
{
   |- !x_1 ... x_m. c v_1 ... v_n = t
}
and is saved in the current theory under
{name}.  Optionally, the definitional term argument
may have any of its variables universally quantified.

\FAILURE
{new_definition} fails if {t} contains free variables that are not
in {x_1}, ..., {x_m} (this is equivalent to requiring
{\v_1 ... v_n. t} to be a closed term). Failure also occurs if
any variable occurs more than once in {v_1, ..., v_n}.  Finally,
failure occurs if there is a type variable in {v_1}, ..., {v_n} or
{t} that does not occur in the type of {c}.

\EXAMPLE
A NAND relation can be defined as follows.
{
   - new_definition (
       "NAND2",
       Term`NAND2 (in_1,in_2) out = !t:num. out t = ~(in_1 t /\ in_2 t)`);

   > val it =
       |- !in_1 in_2 out.
              NAND2 (in_1,in_2) out = !t. out t = ~(in_1 t /\ in_2 t)
       : thm
}


\SEEALSO
Definition.new_specification, boolSyntax.new_binder_definition, boolSyntax.new_infixl_definition, boolSyntax.new_infixr_definition, Prim_rec.new_recursive_definition, TotalDefn.Define.
\ENDDOC