Fix for +-rule-down #15
Conversation
Argument presented in the source code was ;; note: We can't assert that X and Y are integers when Z is an integer since ;; Z may be an integer when X and Y are Gaussian integers. But we can ;; make such an assertion if either X or Y is real. If the Screamer ;; type system could distinguish Gaussian integers from other complex ;; numbers we could make such an assertion whenever either X or Y was ;; not a Gaussian integer. The argument above must surely be incorrect. If Z is an integer, and Y is a real say 2.5 then X will surely not be an integer. The argument *does* work if eithe r X or Y are integers. So changed things so that Z being an integer and X OR Y being an INTEGER means that X AND Y are both integers. (Note the assertion is only for X, but this is correct given that the assertion for Y happens in another call to this rule.
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This is just the text of the original issue that I opened (sorry about the duplication, haven't used github for this sort of thing before) function -v erroneously restricts arguments to integers in certain casesI'm a bit too busy to delve into this issue more deeply at the moment (maybe I'll poke at the screamer sources later, haven't really had a look at them before), but (-v (a-real-betweenv 1.1 1.2)) emits an error. (This form distils the issue I had in much more complicated code) Mysteriously, the real variable created by a-real-between-v has been restricted to be an integer, causing the exception later on. Further investigation reveals (-v 0 (a-real-betweenv 1.1 1.2)) has the same issue, but the following works correctly (-v 0.0 (a-real-betweenv 1.1 1.2)) This can be used as a workaround for anyone similarly affected. In the case of +v, there is seemingly no such problem. (+v (a-real-betweenv 1.1 1.2)) all work correctly. Perhaps this means a fix may be relatively simple? (Note: I'm using the quicklisp screamer-20111105-git distro in case this matters) |
Argument presented in the source code was
;; note: We can't assert that X and Y are integers when Z is an integer since
;; Z may be an integer when X and Y are Gaussian integers. But we can
;; make such an assertion if either X or Y is real. If the Screamer
;; type system could distinguish Gaussian integers from other complex
;; numbers we could make such an assertion whenever either X or Y was
;; not a Gaussian integer.
The argument above must surely be incorrect. If Z is an integer, and Y is a real
say 2.5 then X will surely not be an integer. The argument does work if eithe
r X or Y are integers. So changed things so that Z being an integer and X OR Y being an INTEGER means that X AND Y are both integers. (Note the assertion is only for X, but this is correct given that the assertion for Y happens in another call to this rule.