248   shows "(a\<sharp>(Var b)) = (a\<sharp>b)"

   248   shows "(a\<sharp>(Var b)) = (a\<sharp>b)"

   249   apply(simp add: fresh_def)

   249   apply(simp add: fresh_def)

   250   apply(simp add: var_supp)

   250   apply(simp add: var_supp)

   251   done

   251   done

   252 

   252