cink | CFDG interpreter in Javascript | Interpreter library

You have to use the float() function and then between brackets the input() function. It will try to convert the given input to the float type. If the input value could not be converted to float it will throw a ValueError

The Dafny verifier is willing to expand function definitions when doing a proof, but within some limits. If it did not, then it could not give you quick turnaround when you ask it to prove something that doesn't hold. It may be helpful to think of the verifier as expanding each occurrence of a function that you write once. It actually does more. For example, when the arguments to a function are literals, then the verifier may expand a function beyond the normal limits. (See Amin, Leino, and Rompf, TAP 2014, if you're interested in the details of this "dual-rail encoding".)

To prove your assertion, you'll have to help the verifier along. Add the following proof calculation before the assertion and your program will verify: