Random Sentence Generator is Insufficiently Random #25 solution

[aanyasinghdhaka]

i am a first time contributer please check my pull request if its right

[mr-martian]

Could you explain your changes? I'm not sure what selected_rules is achieving since there's only ever at most one item in it.

[aanyasinghdhaka]

I added selected_rules to stop using the same rule back-to-back when making sentences. It's like a memory that helps the program avoid picking the same rule right after it was just used. This change makes the sentences more different during one turn of the program. But, it doesn't change how rules are picked in different turns. Its job is to avoid doing the same thing again and add a little more variety just for one time the program runs.

[mr-martian]

My reading of the code is the following:

1. to generate the next node of the tree, create an empty set
2. choose a rule at random
3. if the rule is already in the set, return to step 2.
4. generate the chosen rule

Note that because the set is always empty after step 1, the rule chosen in step 2 will never be in it, and thus step 3 will never be relevant.