uptodate_type : hol_type -> bool
STRUCTURE
SYNOPSIS
Tells if a type is out of date.
DESCRIPTION
Operations in the current theory segment of HOL allow one to redefine types and constants. This can cause theorems to become invalid. As a result, HOL has a rudimentary consistency maintenance system built around the notion of whether type operators and term constants are "up-to-date".

An invocation uptodate_type ty, checks ty to see if it has been built from any out of date components, returning false just in case it has. The definition of out-of-date is mutually recursive among types, terms, and theorems. A type variable never out-of-date. A compound type is out-of-date if either (a) its type operator is out-of-date, or (b) any of its argument types are out-of-date. A type operator is out-of-date if it has been re-declared or if the witness theorem used to justify the type in the call to new_type_definition is out-of-date. Only a component of the current theory segment may be out-of-date. All items from ancestor theories are fixed, and unable to be overwritten, thus are always up-to-date.

FAILURE
Never fails.
EXAMPLE
- Hol_datatype `foo = A | B of 'a`;
<<HOL message: Defined type: "foo">>
> val it = () : unit
   
- val ty = Type `:'a foo list`;
> val ty = `:'a foo list` : hol_type

- uptodate_type ty;
> val it = true : bool

- delete_type "foo";
> val it = () : unit

- uptodate_type ty;
> val it = false : bool
SEEALSO
HOL  Kananaskis-10