Catch exceptions arising during the abstraction operation.

Filter out theorems that are "too deep".

Filter out theorems that are "too deep".

Added field ideal into entry - uses by algebra method to prove the ideal membership problem

(1) signatures updated according to normalizer_data.ML (added field ideal in entry);

(2) For a theory the conversions returned are now ring_conv (as before, proves a universal statement), simple_ideal proves ideal membership for one polynomial ; multi_ideal solves the more general ideal membership for several existentially quantifier variables involved in several conjunctions; a simpset containing a simproc to turn x = y into p = 0 where p is the normal form of x - y;

(3) Added ideal_tac a tactic to prove general ideal membership (cf. John Harrision CADE 2007) ;

(4) Added algebra_tac : first tries ring_tac (old algebra) then ideal_tac

(2) For a theory the conversions returned are now ring_conv (as before, proves a universal statement), simple_ideal proves ideal membership for one polynomial ; multi_ideal solves the more general ideal membership for several existentially quantifier variables involved in several conjunctions; a simpset containing a simproc to turn x = y into p = 0 where p is the normal form of x - y;

(3) Added ideal_tac a tactic to prove general ideal membership (cf. John Harrision CADE 2007) ;

(4) Added algebra_tac : first tries ring_tac (old algebra) then ideal_tac

(1) added axiom to ringb and theorems to enable algebra to prove the ideal membership problem; (2) Method algebra now calls algebra_tac which first tries to solve a universal formula, then in case of failure trie to solve the ideal membership problem (see HOL/Tools/Groebner_Basis/groebner.ML)