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The thing that tends to trip people is that the `integer?` predicate is true for both exact integers (like 123) *and* inexact ones (like 123.0), while Typed Racket's `Integer` corresponds only with the exact ones. So usually the easy way out of this is to use `exact-integer?` instead. As a side note, "The `if n` is like a form of pattern matching" -- that's not really true. There's no pattern matching happenning. Instead, once you use a predicate for a specific type with something in an `if`, Typed Racket knows that in the then-branch, something has that type. In the `if n` case, that means that it knows that it cannot be `#f`, and if outside the `if` it was `(U #f Whatever)` then in the then branch it is left as `Whatever`. This is called "occurrence typing".
* Use a plain `for` loop over the input instead of an indirect counter * Use `(cons x y)` to add things on the left side instead of `(append l (list x))` (if you really need to preserve the order, then it's better to `reverse` the lists when you're done reading) * Using plain `'` quote is generally preferred when you don't need the extra features of quasi-quotes * `str->int` is used only in `read-places`, so put it there
…lobal vector. Makes it three times slower, but much more readable code.
(Functional in the proper sense, not in the we-don't-mutate sense.)
Makes it roughly as fast as the global-vector version.
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Roughly same speed, but much better looking code. A bunch of smaller commits with explanations.