MORE PATTERN MATCHING

[danilopedraza]

I need to improve the matcher. Currently thinking of:

• [x] Matching fractions: let numer(a // _) := a
• [x] Matching sets: let pair({a, b}) := (a, b)
• [x] cons over sets: let some({val|_}) := val
• [x] Matching dictionaries (#56): let f({"a": b,..}) := b
• [x] Matching ranges: let len(a..b) := b - a

[danilopedraza]

Before I add more patterns, I will need to do some changes. I need to save the information on what has patterns and what is pure. That will allow me to match expressions faster and do less checks in the matcher.