Assignment 1 – Contracts
Due Wednesday 4/10 11:59pm
1. Add a (non-dependent) contract-out specification for this function and write three calls such that one blames this module, one blames the calling module and one produces a result without any blame.
| #lang racket |
| (define (len l) |
| (cond |
| [(empty? (rest l)) 1] |
| [else (+ 1 (len (rest l)))])) |
2.
Add a dependent contract via contract-out
that ensures that the results of this function
are positive (this contract will disallow some
inputs that the function does not crash on, but that
is okay – just because something does not crash does
not make it work) and that there can never
be blame to the module containing f.
3. The following contract does not capture g’s behavior. Come up with an example call to g that results in a contract violation blaming the following module (which contains g).
| #lang racket |
| (provide |
| (contract-out |
| [g (-> (-> natural? natural?) |
| natural? |
| natural?)])) |
| (define (g f x) |
| (- (f (f x)))) |
4. Without changing the contract on the x argument or on the result of g (so change only the contract on the f argument), adjust the contract so that g cannot be blamed.
Please submit a racket file with your solution via Canvas.