Perhaps you want something like this: Welcome to Racket v6.0.0.1. > (current-print (lambda (x) (if (procedure? x) (printf "~a" (object-name x)) > (print x)) (newline))) #<void> > + + > 10 10
On Jan 4, 2014, at 6:40 PM, Rian Shams wrote: > Sorry for my lack of clarity. > > My question is about the output that is displayed from calling the function. > For example, evaluating just > > >$+ > #<procedure:$+> > > The result I am looking for is > > >$+ > $+ > > as opposed to > #<procedure:$+> > > I am not sure whether this is just a formatting or renaming problem, or if it > is possible to change what the interpreter displays in Dr.Racket? > > I am fairly new to Racket and programming in general and so I really > appreciate your responses and patience. > > > On Sat, Jan 4, 2014 at 5:49 PM, Matthias Felleisen <matth...@ccs.neu.edu> > wrote: > > Yes, you need two functions: one that gives you the name of a procedure and > one that picks a procedure. I was merely hinting at how to do the former. -- > Matthias > > > > On Jan 4, 2014, at 4:57 PM, Rian Shams wrote: > >> Thanks Matthias, >> >> If I use your definition: >> >> (define (select-random-safe-function) >> (object-name >> (list-ref safe-function-set (random (length safe-function-set))))) >> >> then, >> >> >(procedure-arity (select-random-safe-function)) >> error:procedure-arity: contract violation >> expected: procedure? >> given: '$+ >> >> >> I believe I need two things: >> >> 1. (select-random-safe-function) should return an unquoted procedure, >> similar to >> >> (define (select-random-safe-function) ;without object-name >> (list-ref safe-function-set (random (length safe-function-set)))) >> >(select-random-safe-function) >> #<procedure:$+> >> >> preferably without #<procedure: $+ > >> >> so my problem is that I want the output to display >> $+ >> instead of >> #<procedure:$+> >> >> 2. The reason the procedure needs to be unquoted is because >> (procedure-arity (select-random-safe-function)) will produce an error if the >> function is quoted. >> >> >> >> >> Later on I use both (procedure-arity (select-random-safe-function)) and >> (select-random-safe-function) in a main function: >> >> ;;Generate Initial Population >> ;population size is a positive integer and the auxiliary-function, >> generate-chromsome generates a tree using functions from safe-function-set >> and terms (numbers and symbols) from a term-set >> >> (define (generate-initial-population population-size) >> (cond [(zero? population-size) empty] >> [else (cons (generate-chromosome initial-chromosome-depth) >> ;initial-chromosome-depth is 3 >> (generate-initial-population (sub1 >> population-size)))])) >> >> > (generate-initial-population 1) >> '((#<procedure:$/> (#<procedure:$-> x .234) (#<procedure:$+> .576 x))) >> >> this gets me my desired result, but is hard for me to read especially as the >> depth and population size grows (typically I will be working with >> populations ranging in the hundreds or thousands and each chromosome/tree's >> depth could easily exceed 10) so it would be more convenient here if my >> solution displays >> >> '(($/ ($- x .234) ($+ .576 x))) >> >> instead of >> >> '((#<procedure:$/> (#<procedure:$-> x .234) (#<procedure:$+> .576 x))) >> >> and I am not sure how I would go about doing this? >> >> On Sat, Jan 4, 2014 at 8:45 AM, Matthias Felleisen <matth...@ccs.neu.edu> >> wrote: >> >> If you really just want the name, use object-name: >> >> (define (select-random-safe-function) >> (object-name >> (list-ref safe-function-set (random (length safe-function-set))))) >> >> Welcome to DrRacket, version 6.0.0.1--2013-12-29(bbb0c5f6/d) [3m]. >> Language: racket. >> > (select-random-safe-function) >> '$* >> >> >> >> >> On Jan 4, 2014, at 2:48 AM, Rian Shams wrote: >> >>> If I do this I get the results I need for (procedure-arity >>> (select-random-safe-function)), but when I call >>> (safe-function-set) or (select-random-safe-function) or any other function >>> that returns a safe function I get for example: >>> >>> >(safe-function-set) >>> '(#<procedure:$+> #<procedure:$-> #<procedure:$*> #<procedure:$/>) >>> >>> >(select-random-safe-function) >>> #<procedure:$-> >>> >>> whereas when it was defined using quote as opposed to list I get: >>> >>> >(safe-function-set) >>> '($+ $- $* $/) >>> >>> >(select-random-safe-function) >>> '$- >>> >>> How would I get rid of this #<procedure:$-> part for readability, keeping >>> only the $- part which is the actual function I defined, while still >>> keeping it a function/procedure that gives me the function arity using >>> (procedure-arity (select-random-safe-function))? >>> >>> Best, >>> >>> >>> On Fri, Jan 3, 2014 at 5:31 PM, Sam Tobin-Hochstadt <sa...@cs.indiana.edu> >>> wrote: >>> Try replacing `safe-function-set` with: >>> >>> (define safe-function-set (list $+ $- $* $/)) >>> >>> Sam >>> >>> On Fri, Jan 3, 2014 at 5:28 PM, Rian Shams <rian.sh...@gmail.com> wrote: >>> > Hello, >>> > >>> > I am working with functions that I have defined to only take 1 or 2 >>> > operands >>> > (called safe-functions) for the implementation of a genetic program. >>> > >>> > (define ($+ augend addend) ;operation is addition >>> > (+ augend addend)) ; the result is the sum >>> > (define ($- minuend subtrahend) ;operation is subtraction >>> > (- minuend subtrahend)) ;result is difference >>> > (define ($* multiplicand multiplier) ;operation is multiplication >>> > (* multiplicand multiplier)) ;result is product >>> > (define ($/ dividend divisor) ;operation is division >>> > (/ dividend divisor)) ;result is quotient >>> > >>> > (define (infinity? x) (or (eq? x +Inf.0) (eq? x -Inf.0))) >>> > (define ($sin x) (if (infinity? x) (* (sgn x) +Inf.0) (sin x))) >>> > (define ($cos x) (if (infinity? x) (* (sgn x) +Inf.0) (cos x))) >>> > >>> > (define safe-function-set >>> > '($+ >>> > $- >>> > $* >>> > $/ >>> > ;$sin >>> > ;$cos)) >>> > >>> > (define (select-random-safe-function) >>> > (list-ref safe-function-set (random (length safe-function-set)))) >>> > >>> > I would like to use procedure-arity (or a similar function) to determine >>> > the >>> > arity of a randomly selected safe function but I get this error: >>> > >>> >>(procedure-arity (select-random-safe-function)) >>> > error: procedure-arity: contract violation >>> > expected: procedure? >>> > given: '$+ >>> > >>> > I think the problem is that the safe-functions are passed to >>> > procedure-arity >>> > quoted. Is there a way I can unquote the functions, or adjust >>> > procedure-arity to make (procedure-arity (select-random-safe-function)) >>> > work? >>> > >>> > Thanks, >>> > -- >>> > Rian Shams >>> > >>> > ____________________ >>> > Racket Users list: >>> > http://lists.racket-lang.org/users >>> > >>> >>> >>> >>> -- >>> Rian Shams >>> ____________________ >>> Racket Users list: >>> http://lists.racket-lang.org/users >> >> >> >> >> -- >> Rian Shams > > > > > -- > Rian Shams
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