Roelof, As you noted, reverse doesn't preserve the variety of collection which was passed in - it returns a sequence. (into A B) appends the items in B onto A, and will return a collection of the same type as A. (empty A) returns a collection of the same type as A, with no items in it. So with (into (empty A) (reverse A)) we're saying "give me a sequence containing the items in A in reverse order, then conjoin them onto an empty collection having the same type as A".
References: - https://clojuredocs.org/clojure.core/empty - https://clojuredocs.org/clojure.core/into Take care, Moe On Wed, Oct 7, 2015 at 7:33 PM, Roelof Wobben <wobbenroe...@gmail.com> wrote: > Thanks , that did the trick. > > Apperent; string/reverse works different from reverse > > One question : what does into do and does (empty x) means if x is empty > or do you make a empty copy of x. > > Roelof > > > Op woensdag 7 oktober 2015 20:07:00 UTC+2 schreef Moe Aboulkheir: >> >> Roelof, >> >> Something like this: >> >> (defn palindrome [x] >> (if (string? x) >> (clojure.string/reverse x) >> (into (empty x) (reverse x)))) >> >> Alternatively, you may want to consider explicitly using seq on your >> inputs when you get them, and using that of the basis of comparison & input >> to reverse. If you don't actually care about the concrete sequence type >> (i.e. you only want sensible equality semantics after reversing something), >> dropping it as soon as possible may be a better strategy. >> >> Take care, >> Moe >> >> On Wed, Oct 7, 2015 at 6:51 PM, Roelof Wobben <wobben...@gmail.com> >> wrote: >> >>> Hello, >>> >>> I try to solve a problem for 4clojure where I have to make a palingdrome >>> detector. >>> >>> So for trying I did this : >>> >>> (ns fourclojure.core >>> (:gen-class)) >>> >>> >>> (defn palingdrome [string] >>> ( reverse string)) >>> >>> (apply str (palingdrome '( 1 2 3) )) '321' >>> (apply str (palingdrome "Roelof" )) "foleoR" >>> >>> (defn palingdrome2 [string] >>> ( reverse string)) >>> >>> (palingdrome2 '( 1 2 3) ) ( 3 2 1 ) >>> (palingdrome2 "Roelof" ) (\f \o \l \e \o \R) >>> >>> So it works for a map or for a string. >>> >>> Is there a way I can make it work for both ? >>> >>> Roelof >>> >>> >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To post to this group, send email to clo...@googlegroups.com >>> Note that posts from new members are moderated - please be patient with >>> your first post. >>> To unsubscribe from this group, send email to >>> clojure+u...@googlegroups.com >>> For more options, visit this group at >>> http://groups.google.com/group/clojure?hl=en >>> --- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to clojure+u...@googlegroups.com. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
