Typed Exercises 1

1. Use the [ name : Type ] method of specifying a type to write the function sub7 which takes in a number and subtracts 7 from it.l

2. Use the (: name Type) method of specifying a type to write the function triple which takes in a number and triples it.

Write these functions

Use Typed Racket to write these functions. Make sure you write the output type as well as the input types.

1. sq18: take in a number, square it, and subtract 18.
2. sl5: take in a string, return five more than its length.
3. ssl: take in two strings, find the sum of their lengths.

Technical details

Sometimes Number is not restrictive enough. If you mean a number on the number line, you have to tell Racket that you want a Real number. Racket does know about complex numbers!

3. Write a function of two inputs that finds the absolute value of the difference between them.

4. Write a function that takes in two real numbers and returns the one that is larger (try this using cond or if). Technical: Experiment to see if you can use Number as the type. (Why not?)