--- a/src/HOL/Data_Structures/Queue_Spec.thy Fri Oct 16 11:38:55 2020 +0200
+++ b/src/HOL/Data_Structures/Queue_Spec.thy Fri Oct 16 15:09:41 2020 +0200
@@ -11,7 +11,7 @@
locale Queue =
fixes empty :: "'q"
fixes enq :: "'a \<Rightarrow> 'q \<Rightarrow> 'q"
-fixes front :: "'q \<Rightarrow> 'a"
+fixes first :: "'q \<Rightarrow> 'a"
fixes deq :: "'q \<Rightarrow> 'q"
fixes is_empty :: "'q \<Rightarrow> bool"
fixes list :: "'q \<Rightarrow> 'a list"
@@ -19,7 +19,7 @@
assumes list_empty: "list empty = []"
assumes list_enq: "invar q \<Longrightarrow> list(enq x q) = list q @ [x]"
assumes list_deq: "invar q \<Longrightarrow> list(deq q) = tl(list q)"
-assumes list_front: "invar q \<Longrightarrow> \<not> list q = [] \<Longrightarrow> front q = hd(list q)"
+assumes list_first: "invar q \<Longrightarrow> \<not> list q = [] \<Longrightarrow> first q = hd(list q)"
assumes list_is_empty: "invar q \<Longrightarrow> is_empty q = (list q = [])"
assumes invar_empty: "invar empty"
assumes invar_enq: "invar q \<Longrightarrow> invar(enq x q)"