Name the carbonyl compound

You will finish a program that names a straight-chain aldehyde or ketone from the number of carbon atoms and the place of the C=O. Three small parts are missing.

The idea. The C=O at an end of the chain makes an aldehyde, named -al. Inside the chain it makes a ketone, named -one. The number is counted from the end that gives the carbonyl carbon the smaller value.

Your tasks.

1. Complete locant(n, place) so that it returns the smaller of place and n + 1 - place.
2. Complete is_aldehyde(n, place) so that it is true when the C=O is on the first or the last carbon.
3. In name_of, return the right ending for an aldehyde, for propanone or butanone, and for the other ketones.