An Introduction to Functional Programming Through Lambda Calculus

- 88 -• considered repetitive type checking, and static and dynamic typing• introduced notation for strictly bracketed infix expressions• introduced notation for case definitions and structure matchingSome of these topics are summarised below.IF ... THEN ... ELSE ...IF THEN ELSE ==COND Infix operators == Note that strict bracketing is required for nested infix expressions.Boolean case definitiondef TRUE = or FALSE = ==def =IF THEN ELSE Number case definitionrec 0 = or (SUCC ) = ==rec =IF ISZERO THEN ELSE 5.15. Exercises1) Evaluate fully the following expressions:i) ISBOOL 3ii) ISNUMB FALSEiii) NOT 1iv) TRUE AND 2v) 2 + TRUE2) Signed numbers might be introduced as a new type with an extra layer of ‘pairing’ so that a numbers’s value ispreceded by a boolean to indicate whether or not the number is positive or negative: