--- a/src/FOL/ex/Propositional_Int.thy Thu Jul 23 14:20:51 2015 +0200
+++ b/src/FOL/ex/Propositional_Int.thy Thu Jul 23 14:25:05 2015 +0200
@@ -3,13 +3,13 @@
Copyright 1991 University of Cambridge
*)
-section {* First-Order Logic: propositional examples (intuitionistic version) *}
+section \<open>First-Order Logic: propositional examples (intuitionistic version)\<close>
theory Propositional_Int
imports IFOL
begin
-text {* commutative laws of @{text "&"} and @{text "|"} *}
+text \<open>commutative laws of @{text "&"} and @{text "|"}\<close>
lemma "P & Q --> Q & P"
by (tactic "IntPr.fast_tac @{context} 1")
@@ -18,7 +18,7 @@
by (tactic "IntPr.fast_tac @{context} 1")
-text {* associative laws of @{text "&"} and @{text "|"} *}
+text \<open>associative laws of @{text "&"} and @{text "|"}\<close>
lemma "(P & Q) & R --> P & (Q & R)"
by (tactic "IntPr.fast_tac @{context} 1")
@@ -26,7 +26,7 @@
by (tactic "IntPr.fast_tac @{context} 1")
-text {* distributive laws of @{text "&"} and @{text "|"} *}
+text \<open>distributive laws of @{text "&"} and @{text "|"}\<close>
lemma "(P & Q) | R --> (P | R) & (Q | R)"
by (tactic "IntPr.fast_tac @{context} 1")
@@ -40,7 +40,7 @@
by (tactic "IntPr.fast_tac @{context} 1")
-text {* Laws involving implication *}
+text \<open>Laws involving implication\<close>
lemma "(P-->R) & (Q-->R) <-> (P|Q --> R)"
by (tactic "IntPr.fast_tac @{context} 1")
@@ -58,18 +58,18 @@
by (tactic "IntPr.fast_tac @{context} 1")
-text {* Propositions-as-types *}
+text \<open>Propositions-as-types\<close>
--- {* The combinator K *}
+-- \<open>The combinator K\<close>
lemma "P --> (Q --> P)"
by (tactic "IntPr.fast_tac @{context} 1")
--- {* The combinator S *}
+-- \<open>The combinator S\<close>
lemma "(P-->Q-->R) --> (P-->Q) --> (P-->R)"
by (tactic "IntPr.fast_tac @{context} 1")
--- {* Converse is classical *}
+-- \<open>Converse is classical\<close>
lemma "(P-->Q) | (P-->R) --> (P --> Q | R)"
by (tactic "IntPr.fast_tac @{context} 1")
@@ -77,7 +77,7 @@
by (tactic "IntPr.fast_tac @{context} 1")
-text {* Schwichtenberg's examples (via T. Nipkow) *}
+text \<open>Schwichtenberg's examples (via T. Nipkow)\<close>
lemma stab_imp: "(((Q-->R)-->R)-->Q) --> (((P-->Q)-->R)-->R)-->P-->Q"
by (tactic "IntPr.fast_tac @{context} 1")