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15 include "delayed_updating/syntax/path.ma".
16 include "delayed_updating/notation/relations/predicate_p_tail_1.ma".
17 include "ground/xoa/ex_1_2.ma".
19 (* PROPER CONDITION FOR PATH ************************************************)
21 definition ppc: predicate path ā
26 "proper condition (path)"
27 'PredicatePTail p = (ppc p).
29 (* Basic constructions ******************************************************)
31 lemma ppc_lcons (l) (q): ź(lāq).
35 (* Basic inversions ********************************************************)
37 lemma ppc_inv_lcons (p):
38 źp ā āāl,q. lāq = p.
41 | #l #q #_ /2 width=3 by ex1_2_intro/