Error in Exercise 1.5 of "Programming in Cryptol" Textbook

[manleykm]

Towards the top of page 10 in the "Programming in Cryptol" Textbook, there is an exercise which states:

Exercise 1.5. Compare the results of evaluating (5 : Z 7) + (6 : Z 7) with toInteger (5 : Z 7) + toInteger
(6 : Z 7) . What is the result of -3 : Z 7 ? Were the results what you expected?

However, entering 'toInteger (5 : Z 7) + toInteger (6 : Z 7)' into Cryptol results in the following error:

  Unsolvable constraints:
    • Integral (Z 7)
        arising from
        use of expression toInteger
        at <interactive>:1:23--1:32
    • Reason: Type 'Z 7' is not an integral type.

The textbook's answer manual at the end of the book claims that Cryptol should give an answer of 11.

[brianhuffman]

It looks like this was broken when we rearranged the type classes for cryptol 2.9. These uses of toInteger will need to be changed to fromZ, which has the appropriate type.

[brianhuffman]

See also #613.