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
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