[STATEMENT]
lemma f_values: "(f 0 = 0 \<or> f 0 = 1) \<and> (f 1 = 0 \<or> f 1 = 1)"
[PROOF STATE]
proof (prove)
goal (1 subgoal):
 1. (f 0 = 0 \<or> f 0 = 1) \<and> (f 1 = 0 \<or> f 1 = 1)
[PROOF STEP]
using dom
[PROOF STATE]
proof (prove)
using this:
f \<in> {0, 1} \<rightarrow>\<^sub>E {0, 1}

goal (1 subgoal):
 1. (f 0 = 0 \<or> f 0 = 1) \<and> (f 1 = 0 \<or> f 1 = 1)
[PROOF STEP]
by auto