# Chapter 2 Exercise Set 2

`double(n)`

Write a function, `double`, that takes an argument, `n`, and returns twice
the value of `n`.

`compare(a, b)`

Write a `compare(a, b)` function that returns `1` if `a > b`, `0`
if `a == b`, and `-1` if `a < b`.

`isEven(n)`

Write a function `isEven` that takes an integer, `n`, as an argument and
returns `true` if `n` is even and `false` otherwise.

`isFactor(f, n)`

Write a function `isFactor` that takes two integers, `f` and `n`, as
arguments and returns `true` if `f` is a factor of `n` and `false`
otherwise.

`f2c(t)` and `c2f(t)`

Write a function `f2c` that takes a tempurature, `t` in Fahrenheit as an
argument and returns the equivalent temperature in Celsius. Then write a
function `c2f` that does the opposite conversion.

`isDigit(ch)`

Write an `isDigit` function that takes a character, `ch`, as an argument
and returns `true` if `ch` is a digit (a *character* between `'0'` and
`'9'`) and false otherwise.