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\DOC new_definition
\TYPE {new_definition : term -> thm}
\SYNOPSIS
Declare a new constant and a definitional axiom.
\DESCRIBE
The function {new_definition} provides a facility for definitional extensions.
It takes a term giving the desired definition. The value returned by
{new_definition} is a theorem stating 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 `c v_1 ... v_n = t`}, where {c} is a
variable whose name is not already used as a constant, declares {c} to be a new
constant and returns the theorem:
{
|- !x_1 ... x_m. c v_1 ... v_n = t
}
Optionally, the definitional term argument may have any of its variables
universally quantified.
\FAILURE
{new_definition} fails if {c} is already a constant or if the definition does
not have the right form.
\EXAMPLE
A NAND relation on signals indexed by `time' can be defined as follows.
{
# new_definition
`NAND2 (in_1,in_2) out <=> !t:num. out t <=> ~(in_1 t /\ in_2 t)`;;
val it : thm =
|- !out in_1 in_2.
NAND2 (in_1,in_2) out <=> (!t. out t <=> ~(in_1 t /\ in_2 t))
}
\COMMENTS
Note that the conclusion of the theorem returned is essentially the same as the
term input by the user, except that {c} was a variable in the original term but
is a constant in the returned theorem. The function {define} is significantly
more flexible in the kinds of definition it allows, but for some purposes this
more basic principle is fine.
\SEEALSO
define, new_basic_definition, new_inductive_definition,
new_recursive_definition, new_specification.
\ENDDOC
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