(* Title : PReal.thy
ID : $Id$
Author : Jacques D. Fleuriot
Copyright : 1998 University of Cambridge
Description : The positive reals as Dedekind sections of positive
rationals. Fundamentals of Abstract Analysis [Gleason- p. 121]
provides some of the definitions.
*)
PReal = PRat +
typedef preal = "{A::prat set. {} < A & A < {q::prat. True} &
(!y: A. ((!z. z < y --> z: A) &
(? u: A. y < u)))}" (preal_1)
instance
preal :: {ord, plus, times}
constdefs
preal_of_prat :: prat => preal
"preal_of_prat q == Abs_preal({x::prat. x < q})"
pinv :: preal => preal
"pinv(R) == Abs_preal({w. ? y. w < y & qinv y ~: Rep_preal(R)})"
psup :: preal set => preal
"psup(P) == Abs_preal({w. ? X: P. w: Rep_preal(X)})"
defs
preal_add_def
"R + S == Abs_preal({w. ? x: Rep_preal(R). ? y: Rep_preal(S). w = x + y})"
preal_mult_def
"R * S == Abs_preal({w. ? x: Rep_preal(R). ? y: Rep_preal(S). w = x * y})"
preal_less_def
"R < (S::preal) == Rep_preal(R) < Rep_preal(S)"
preal_le_def
"R <= (S::preal) == Rep_preal(R) <= Rep_preal(S)"
end