Making a correction here, my wish error message should say this. * in: the 1st argument of* * (->** * ((and/c number? (between/c 0 1)))* * (#:clamp-range boolean?)* * number?)*
Because I understand that the phrase *"the range of"* means the last item in the -> form which is the ->* contract. On Fri, Oct 3, 2014 at 10:55 PM, Alexander McLin <alex.mc...@gmail.com> wrote: > Actually I wasn't quite ready to move on. > > When I apply (curve 3) where (define curve (cubic-bezier a b) a and b are > bezier-control-point? > > I get the following contract error: > > --------------------------------------------------------------------------- > *(curve 3)* > *. . cubic-bezier: contract violation* > * expected: (and/c number? (between/c 0 1))* > * given: 3* > * which isn't: (between/c 0 1)* > * in: the 1st argument of* > * the range of* > * (->* > * bezier-control-point?* > * bezier-control-point?* > * (->** > * ((and/c number? (between/c 0 1)))* > * (#:clamp-range boolean?)* > * number?))* > * contract from: * > * /home/alexander/Workspace/Racket/cubic-bezier.rkt* > * blaming: /home/alexander/Workspace/Racket/experimental.rkt* > * at: /home/alexander/Workspace/Racket/cubic-bezier.rkt:8.11* > > > ---------------------------------------------------------------------------- > > Is there a way I can fine-tune the error message so instead of saying > > * in: the 1st argument of* > * the range of* > * (->* > * bezier-control-point?* > * bezier-control-point?* > * (->** > * ((and/c number? (between/c 0 1)))* > * (#:clamp-range boolean?)* > * number?))* > > It says > > * in: the 1st argument of* > * the range of* > * (->** > * ((and/c number? (between/c 0 1)))* > * (#:clamp-range boolean?)* > * number?)* > > The above contract is really what is coming into play here when using > curve, the surrounding -> form is a distraction and I stare at it for a few > moments mentally parsing to find the right part that is being violated. The > -> contract is only relevant to cubic-bezier and I think confusing because > the lambda that is returned from cubic-bezier may be called after some time > has passed and — at least for me — cubic-bezier is long since gone, and > thus out of mind. > > Alexander McLin > > > > On Fri, Oct 3, 2014 at 9:59 PM, Alexander McLin <alex.mc...@gmail.com> > wrote: > >> Good evening Mathias, >> >> After studying your program and mine, and running various permutations, I >> understand where I was going wrong. It appears that while doing manual >> experimentation I had gotten confused to which module I was actually in the >> REPL when calling various functions by hand. Also my test cases weren't >> fine grained enough to detect each unique contract violation generated by >> suitable bad inputs. >> >> Thanks Mathias! Your examples have helped to sharpen my understanding of >> how contract boundaries work. >> >> Alex >> >> On Thu, Oct 2, 2014 at 2:36 PM, Matthias Felleisen <matth...@ccs.neu.edu> >> wrote: >> >>> >>> If you use this as the program: >>> >>> #lang racket >>> >>> ;; contracts set up boundaries between two regions of a program, say two >>> modules >>> >>> ;; >>> --------------------------------------------------------------------------------------------------- >>> ;; the library >>> (provide (contract-out >>> [struct bezier-control-point ((x (and/c number? (between/c 0 >>> 1))) (y number?))] >>> [cubic-bezier (-> bezier-control-point? >>> bezier-control-point? >>> (->* ((and/c number? (between/c 0 1))) >>> (#:clamp-range boolean?) >>> number?))])) >>> >>> (struct bezier-control-point (x y) #:transparent) >>> >>> (define (cubic-bezier a b) >>> ;; now produce a curve via Bezier triangulation >>> (lambda (x #:clamp-range [cr #f]) >>> x)) >>> >>> ;; >>> --------------------------------------------------------------------------------------------------- >>> ;; the module that uses it >>> (module+ test >>> (require (submod "..")) >>> >>> (define a (bezier-control-point 0.1 5.0)) >>> (define b (bezier-control-point 0.3 9.0)) >>> >>> ((cubic-bezier a b) >>> ;; a contract violation because i isn't comparable >>> (sqrt -1))) >>> >>> >>> drracket or raco test file.rkt will show contract errors. >>> >>> >>> >>> >>> On Oct 2, 2014, at 1:50 PM, Alexander McLin <alex.mc...@gmail.com> >>> wrote: >>> >>> > Spencer, I'm calling cubic-bezier from within a (module+ test (require >>> submod "..")...) form that itself is defined in the file where cubic-bezier >>> is defined. Also I tried from within REPL and requiring the code file. >>> > >>> > Matthias, >>> > >>> > I ran your example and it works exactly the way I wanted. The lambda >>> returned from cubic-bezier properly raises contract violations when bad >>> inputs are given for the required parameter and optional keyword. >>> > >>> > Examining the differences between your example and my original >>> implementation, my functions are directly defined in top level in the file, >>> after #lang racket, not wrapped within a module. And I'm running my test >>> cases within a (module+ test (require submod "..")) form. >>> > >>> > In my test cases within (module+ test...), violations are correctly >>> reported when I give bad inputs to cubic-bezier and bezier-control-point >>> structs. Except the lambda, no violations are reported with bad inputs. Is >>> it because I'm incorrectly using modules? I had thought that module+ and >>> (require submod "..") would allow the contract system to come into full >>> force. >>> > >>> > >>> > >>> > On Thu, Oct 2, 2014 at 9:20 AM, Matthias Felleisen < >>> matth...@ccs.neu.edu> wrote: >>> > >>> > Let's make Spencer's question concrete. Say we have this situation: >>> > >>> > #lang racket >>> > >>> > ;; contracts set up boundaries between two regions of a program, say >>> two modules >>> > >>> > ;; >>> --------------------------------------------------------------------------------------------------- >>> > ;; the library >>> > (module server racket >>> > (provide (contract-out >>> > [struct bezier-control-point ((x (and/c number? (between/c >>> 0 1))) (y number?))] >>> > [cubic-bezier (-> bezier-control-point? >>> > bezier-control-point? >>> > (->* ((and/c number? (between/c 0 1))) >>> > (#:clamp-range boolean?) >>> > number?))])) >>> > >>> > (struct bezier-control-point (x y) #:transparent) >>> > >>> > (define (cubic-bezier a b) >>> > ;; now produce a curve via Bezier triangulation >>> > (lambda (x #:clamp-range [cr #f]) >>> > x))) >>> > >>> > ;; >>> --------------------------------------------------------------------------------------------------- >>> > ;; the module that uses it >>> > (module client racket >>> > (require (submod ".." server)) >>> > >>> > (define a (bezier-control-point 0.1 5.0)) >>> > (define b (bezier-control-point 0.3 9.0)) >>> > >>> > ((cubic-bezier a b) >>> > ;; a contract violation because i isn't comparable >>> > (sqrt -1))) >>> > >>> > ;; >>> --------------------------------------------------------------------------------------------------- >>> > ;; run program run >>> > (require 'client) >>> > >>> > I assume you want to see other violations. Can you explain with this >>> example w/o going into Bezier? >>> > (I just know enough about Bezier to draw curves.) >>> > >>> > -- Matthias >>> > >>> > >>> > >>> > >>> > On Oct 1, 2014, at 10:46 PM, Alexander McLin <alex.mc...@gmail.com> >>> wrote: >>> > >>> > > Hello, >>> > > >>> > > I've been working on a sample project to better understand how to >>> use the contract system. I created a simple Bezier curve implementation and >>> am using (provide (contract-out...) to attach contracts to the provided >>> bindings. >>> > > >>> > > Basically I have a procedure called cubic-bezier that accepts two >>> control point structs used to define the curve. It returns another >>> procedure that actually generates the curve, it accepts an integer >>> parameter that lies on [0, 1] and an optional keyword #:clamp-range. The >>> generator procedure returns a number. >>> > > >>> > > The control point structure is a simple posn type that accepts X and >>> Y fields where X must be between 0 and 1, and Y is allowed to be any number. >>> > > >>> > > Here are the contracts I defined provisionally: >>> > > >>> > > (provide (contract-out >>> > > [struct bezier-control-point ((x (and/c number? (between/c >>> 0 1))) >>> > > (y number?))] >>> > > [cubic-bezier (-> bezier-control-point? >>> > > bezier-control-point? >>> > > (->* ((and/c number? (between/c >>> 0 1))) >>> > > (#:clamp-range boolean?) >>> > > number?))])) >>> > > >>> > > For the contract attached to cubic-bezier using ->, my thinking was >>> to use ->* to generate the contract for the procedure returned by >>> cubic-bezier but it's not working, meaning I'm not getting the any contract >>> violations I'm expecting when giving bad inputs to cubic-bezier's value. >>> > > >>> > > How can I attach a more complex contract to cubic-bezier's value? >>> > > >>> > > Thank you >>> > > Alexander McLin >>> > > ____________________ >>> > > Racket Users list: >>> > > http://lists.racket-lang.org/users >>> > >>> > >>> >>> >> >
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