Booleans

• $ |B = ( { tt, ff }, { \neg, / \/ } )$
• $ eval_{|B} : T_{Bool} -> |B = { or |-> \/, and |-> / not |-> \neg }$

Natural numbers

• $ |N = ( \nat , { ++ , + , \star } ) $
• $ eval_{|N} : T_{Nat} -> |N = { S |-> ++ , mul |-> \star, plus |-> + }$