Checkable arrows

• =>

  The claim checks out only if extended equality produces a truthy value.

  (fact (nth-prime 100) => odd?)

• =not=> or =deny=>

  The claim checks out only if extended equality does not produce a truthy value.

  (fact (nth-prime 100) =not=> even?)

• =expands-to=>

  The left-hand side is macroexpanded and compared to the right-hand side:

  (fact (when true 3) =expands-to=> (if true (do 3)))

  Note that neither side is quoted.

• =future=>

  Acts like future facts in that it produces a "WORK TO DO" message. This is useful when you've got most of the claims in a fact working, but have to defer finishing one or a few.