doc-src/ZF/FOL_examples.thy

more efficient Markup_Tree, based on branches sorted by quasi-order;
renamed markup_node.scala to markup_tree.scala and classes/objects accordingly;
Position.Range: produce actual Text.Range;
Symbol.Index.decode: convert 1-based Isabelle offsets here;
added static Command.range;
simplified Command.markup;
Document_Model.token_marker: flatten markup at most once;
tuned;

header{*Examples of Classical Reasoning*}

theory FOL_examples imports FOL begin

lemma "EX y. ALL x. P(y)-->P(x)"
  --{* @{subgoals[display,indent=0,margin=65]} *}
apply (rule exCI)
  --{* @{subgoals[display,indent=0,margin=65]} *}
apply (rule allI)
  --{* @{subgoals[display,indent=0,margin=65]} *}
apply (rule impI)
  --{* @{subgoals[display,indent=0,margin=65]} *}
apply (erule allE)
  --{* @{subgoals[display,indent=0,margin=65]} *}
txt{*see below for @{text allI} combined with @{text swap}*}
apply (erule allI [THEN [2] swap])
  --{* @{subgoals[display,indent=0,margin=65]} *}
apply (rule impI)
  --{* @{subgoals[display,indent=0,margin=65]} *}
apply (erule notE)
  --{* @{subgoals[display,indent=0,margin=65]} *}
apply assumption
done

text {*
@{thm[display] allI [THEN [2] swap]}
*}

lemma "EX y. ALL x. P(y)-->P(x)"
by blast

end