equal
deleted
inserted
replaced
153 |
153 |
154 lemma "{x. P x \<longrightarrow> Q x} = -{x. P x} \<union> {x. Q x}" |
154 lemma "{x. P x \<longrightarrow> Q x} = -{x. P x} \<union> {x. Q x}" |
155 by blast |
155 by blast |
156 |
156 |
157 definition prime :: "nat set" where |
157 definition prime :: "nat set" where |
158 "prime == {p. 1<p & (ALL m. m dvd p --> m=1 | m=p)}" |
158 "prime == {p. 1<p & (\<forall>m. m dvd p \<longrightarrow> m=1 \<or> m=p)}" |
159 |
159 |
160 lemma "{p*q | p q. p\<in>prime \<and> q\<in>prime} = |
160 lemma "{p*q | p q. p\<in>prime \<and> q\<in>prime} = |
161 {z. \<exists>p q. z = p*q \<and> p\<in>prime \<and> q\<in>prime}" |
161 {z. \<exists>p q. z = p*q \<and> p\<in>prime \<and> q\<in>prime}" |
162 by (rule refl) |
162 by (rule refl) |
163 |
163 |