inst : hol_type subst -> term -> term

SYNOPSIS

Performs type instantiations in a term.

DESCRIBE

The function inst should be used as follows:

   inst [{redex_1, residue_1},...,{redex_n, residue_n}] tm

where each `redex' is a hol_type variables, and each `residue' is a hol_type and tm a term to be type-instantiated. This call will replace each occurrence of a redex in tm by its associated residue. Replacement is done in parallel, i.e., once a redex has been replaced by its residue, at some place in the term, that residue at that place will not itself be replaced in the current call. Bound term variables may be renamed in order to preserve the term structure.

FAILURE

Never fails. A redex that is not a variable is simply ignored.

EXAMPLE

- show_types := true;
> val it = () : unit

- let val tm = Term`(x:'a) = (x:'a)`
  in inst [{redex = alpha, residue = Type`:num`}] tm
  end;
> val it = `(x :num) = x` : term

- try (inst [{redex = bool, residue = Type`:num`}]) (Term`x:bool`);
> val it = `(x :bool)` : term

- let val x1 = Term`x:bool`
      val x2 = Term`x:'a`
  in inst [alpha |-> bool] (mk_abs(x1,x2))
  end;
> val it = `\(x' :bool). (x :bool)` : term

USES

Performing internal functions connected with type instantiation.

SEEALSO  type_subst,   Compat.inst_type,   INST_TYPE