Thank you, Robby, This clarifies it a little bit. So far I've avoided reading about the racket module system in details, but I think now is as good time as ever. April 7, 2021 10:40 PM, "Robby Findler" <ro...@cs.northwestern.edu (mailto:ro...@cs.northwestern.edu?to=%22Robby%20Findler%22%20<ro...@cs.northwestern.edu>)> wrote: The short answer: you probably should use (provide (contract-out....)) instead of define/contract.
The slightly longer answer: when you write a contract, you are not just describing what the legal inputs and outputs are, you are also establishing a *boundary* between two regions of code. In the case of define/contract, you are establishing a boundary between the function (here: f) and the module that it contains (here the file "a.rkt"). In the case of (provide (contract-out ...)) the boundary is between a.rkt and b.rkt. The slightly uncomfortable answer: it is my (not completely solid yet) opinion that the boundary that is drawn for define/contract is perhaps not the right / best one. In a theoretical/mathematical sense it is a completely fine and completely defensible one. But it trips people up sometimes. (There are examples others have posted in the past that are perhaps even stranger than yours but boil down to the same specific design choice for define/contract.) Robby On Wed, Apr 7, 2021 at 2:10 PM epi via Racket Users <racket-users@googlegroups.com (mailto:racket-users@googlegroups.com)> wrote: Hello Racket users, I am trying to understand a contract violation message that I am getting. Here is the file a.rkt: #lang racket (provide f) (define/contract (f a) (-> boolean? any/c) '()) and this is b.rkt: #lang racket (require "a.rkt") (f 3) I would expect that the caller is blamed for the contract violation, but the error message that I get is as follows: f: contract violation expected: boolean? given: 3 in: the 1st argument of (-> boolean? any/c) contract from: (function f) blaming: /home/epi/snippets/a.rkt (assuming the contract is correct) at: /home/epi/snippets/a.rkt:3.18 context...: /usr/share/racket/collects/racket/contract/private/blame.rkt:347:0: raise-blame-error /usr/share/racket/collects/racket/contract/private/arrow-higher-order.rkt:379:33 body of "/home/dan/snippets/blameme.rkt" So, I am a bit surprised that the error message blames the file a.rkt. What am I missing here? -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com (mailto:racket-users%2bunsubscr...@googlegroups.com). To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/149cfc632cd666ff1a92177dce90296b%40disroot.org (https://groups.google.com/d/msgid/racket-users/149cfc632cd666ff1a92177dce90296b%40disroot.org). -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/78a0d4875c1fa7ac222a938c3f061588%40disroot.org.
