An Introduction to Functional Programming Through Lambda Calculus

- 165 -to indicate both integer and real so these operators types might be:fn : (num * num) -> numas they take two numeric arguments, with infix syntax for a tuple, and return a numeric result.Note that for each operator both arguments must be the same type.The infix operator:divis for integer division. We can use op to convert it to prefix form to display its type:- op div;> fn : (int * int) -> intArithmetic expressions are built from these operators with the brackets ( and ), for example:- 6 * 7 div (7 - 4) + 28;> 42 : intNote that there is no strict bracketing. The usual precedence:before:before:applies.( )div *+ -The numeric negation operator is:˜again with effective type:fn : num -> numas it is overloaded for use with integers and reals.9.9. String standard functionsThe binary infix operator:ˆconcatenates two strings together:- op ˆ;> fn : (string * string) -> string