Re: Like "if", but it composes functions
Function composition similar to that has been explored a lot in the haskell world. See: http://www.haskell.org/haskellwiki/Arrow I also made a small library to implement some of the operators: https://github.com/odyssomay/clj-arrow I think the reason arrows are so interesting in haskell is because they generalize monads. However, in clojure I have found them to make code harder to write/read rather than easier, so I kind of gave up the concept after a while (and haven't updated the library). Although it's possible that they are actually highly useful and I've just missed something. Jonathan On Wed, Feb 20, 2013 at 3:55 PM, James MacAulay wrote: > Ben: of course, haha...making it a macro seems rather silly now :P > > Alan: I didn't know about useful before, thanks for the pointer! fix and > to-fix look great. > > -- > -- > 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/groups/opt_out. > > > -- -- 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/groups/opt_out.
Re: Like "if", but it composes functions
Ben: of course, haha...making it a macro seems rather silly now :P Alan: I didn't know about useful before, thanks for the pointer! fix and to-fix look great. -- -- 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/groups/opt_out.
Re: Like "if", but it composes functions
2013/2/20 Alan Malloy : > You can use fix to take some data that might not be right (say, an integer > that might actually be a string) and "fix" it by applying read-string: (fix > "10" string? read-string). to-fix returns a function you can use to fix > things. OK, I thought there was some more generic meaning to it (for the OP's initial need, I'm not sure the name fix would convey appropriate semantics, for instance) Cheers > > > On Wednesday, February 20, 2013 12:06:36 AM UTC-8, Laurent PETIT wrote: >> >> Hello, >> >> Why the names fix / to-fix ? >> >> 2013/2/20 Alan Malloy : >> > Useful has functions that do this and more: fix or to-fix, according to >> > taste. Your iffn is just the three-argument case of to-fix: (def magnify >> > (to-fix pos? inc dec)). But fix and to-fix accept more or fewer >> > arguments as >> > well, so that (fix x pos? inc) is like (if (pos? x) (inc x) x), and >> > (to-fix >> > tall? shorten thin? fatten) is (fn [x] (cond (tall? x) (shorten x) >> > (thin? x) >> > (fatten x) :else x)). >> > >> > Basically both of these functions look through their clause pairs and >> > apply >> > the first transform whose test matches. fix takes its "focus" argument >> > immediately, while to-fix returns a lambda that performs the requested >> > operation. >> > >> > >> > On Tuesday, February 19, 2013 9:53:57 PM UTC-8, James MacAulay wrote: >> >> >> >> Sometimes I find myself writing code like this: >> >> >> >> (defn magnify [n] (if (pos? n) (inc n) (dec n))) >> >> >> >> ...and I want to get rid of all those "n"s. I've looked for a macro >> >> like >> >> this, but couldn't find it, so I wrote it: >> >> >> >> https://gist.github.com/jamesmacaulay/4993062 >> >> >> >> Using that, I could re-write the above like this: >> >> >> >> (def magnify (iffn pos? inc dec)) >> >> >> >> I can imagine a condfn macro, too: >> >> >> >> (def magnify2 (condfn pos? inc >> >> neg? dec >> >> :else identity) >> >> >> >> Has this kind of conditional function composition been explored much? I >> >> couldn't find anything like it in the standard library, but maybe I >> >> wasn't >> >> looking hard enough. >> >> >> >> Cheers, >> >> James >> > >> > -- >> > -- >> > 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/groups/opt_out. >> > >> > > > -- > -- > 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/groups/opt_out. > > -- -- 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/groups/opt_out.
Re: Like "if", but it composes functions
You can use fix to take some data that might not be right (say, an integer that might actually be a string) and "fix" it by applying read-string: (fix "10" string? read-string). to-fix returns a function you can use to fix things. On Wednesday, February 20, 2013 12:06:36 AM UTC-8, Laurent PETIT wrote: > > Hello, > > Why the names fix / to-fix ? > > 2013/2/20 Alan Malloy >: > > Useful has functions that do this and more: fix or to-fix, according to > > taste. Your iffn is just the three-argument case of to-fix: (def magnify > > (to-fix pos? inc dec)). But fix and to-fix accept more or fewer > arguments as > > well, so that (fix x pos? inc) is like (if (pos? x) (inc x) x), and > (to-fix > > tall? shorten thin? fatten) is (fn [x] (cond (tall? x) (shorten x) > (thin? x) > > (fatten x) :else x)). > > > > Basically both of these functions look through their clause pairs and > apply > > the first transform whose test matches. fix takes its "focus" argument > > immediately, while to-fix returns a lambda that performs the requested > > operation. > > > > > > On Tuesday, February 19, 2013 9:53:57 PM UTC-8, James MacAulay wrote: > >> > >> Sometimes I find myself writing code like this: > >> > >> (defn magnify [n] (if (pos? n) (inc n) (dec n))) > >> > >> ...and I want to get rid of all those "n"s. I've looked for a macro > like > >> this, but couldn't find it, so I wrote it: > >> > >> https://gist.github.com/jamesmacaulay/4993062 > >> > >> Using that, I could re-write the above like this: > >> > >> (def magnify (iffn pos? inc dec)) > >> > >> I can imagine a condfn macro, too: > >> > >> (def magnify2 (condfn pos? inc > >> neg? dec > >> :else identity) > >> > >> Has this kind of conditional function composition been explored much? I > >> couldn't find anything like it in the standard library, but maybe I > wasn't > >> looking hard enough. > >> > >> Cheers, > >> James > > > > -- > > -- > > 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/groups/opt_out. > > > > > -- -- 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/groups/opt_out.
Re: Like "if", but it composes functions
Hello, Why the names fix / to-fix ? 2013/2/20 Alan Malloy : > Useful has functions that do this and more: fix or to-fix, according to > taste. Your iffn is just the three-argument case of to-fix: (def magnify > (to-fix pos? inc dec)). But fix and to-fix accept more or fewer arguments as > well, so that (fix x pos? inc) is like (if (pos? x) (inc x) x), and (to-fix > tall? shorten thin? fatten) is (fn [x] (cond (tall? x) (shorten x) (thin? x) > (fatten x) :else x)). > > Basically both of these functions look through their clause pairs and apply > the first transform whose test matches. fix takes its "focus" argument > immediately, while to-fix returns a lambda that performs the requested > operation. > > > On Tuesday, February 19, 2013 9:53:57 PM UTC-8, James MacAulay wrote: >> >> Sometimes I find myself writing code like this: >> >> (defn magnify [n] (if (pos? n) (inc n) (dec n))) >> >> ...and I want to get rid of all those "n"s. I've looked for a macro like >> this, but couldn't find it, so I wrote it: >> >> https://gist.github.com/jamesmacaulay/4993062 >> >> Using that, I could re-write the above like this: >> >> (def magnify (iffn pos? inc dec)) >> >> I can imagine a condfn macro, too: >> >> (def magnify2 (condfn pos? inc >> neg? dec >> :else identity) >> >> Has this kind of conditional function composition been explored much? I >> couldn't find anything like it in the standard library, but maybe I wasn't >> looking hard enough. >> >> Cheers, >> James > > -- > -- > 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/groups/opt_out. > > -- -- 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/groups/opt_out.
Re: Like "if", but it composes functions
Sorry, forgot to link to useful: https://github.com/flatland/useful/blob/develop/src/flatland/useful/fn.clj#L30 On Tuesday, February 19, 2013 9:53:57 PM UTC-8, James MacAulay wrote: > > Sometimes I find myself writing code like this: > > (defn magnify [n] (if (pos? n) (inc n) (dec n))) > > ...and I want to get rid of all those "n"s. I've looked for a macro like > this, but couldn't find it, so I wrote it: > > https://gist.github.com/jamesmacaulay/4993062 > > Using that, I could re-write the above like this: > > (def magnify (iffn pos? inc dec)) > > I can imagine a condfn macro, too: > > (def magnify2 (condfn pos? inc > neg? dec > :else identity) > > Has this kind of conditional function composition been explored much? I > couldn't find anything like it in the standard library, but maybe I wasn't > looking hard enough. > > Cheers, > James > -- -- 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/groups/opt_out.
Re: Like "if", but it composes functions
Useful has functions that do this and more: fix or to-fix, according to taste. Your iffn is just the three-argument case of to-fix: (def magnify (to-fix pos? inc dec)). But fix and to-fix accept more or fewer arguments as well, so that (fix x pos? inc) is like (if (pos? x) (inc x) x), and (to-fix tall? shorten thin? fatten) is (fn [x] (cond (tall? x) (shorten x) (thin? x) (fatten x) :else x)). Basically both of these functions look through their clause pairs and apply the first transform whose test matches. fix takes its "focus" argument immediately, while to-fix returns a lambda that performs the requested operation. On Tuesday, February 19, 2013 9:53:57 PM UTC-8, James MacAulay wrote: > > Sometimes I find myself writing code like this: > > (defn magnify [n] (if (pos? n) (inc n) (dec n))) > > ...and I want to get rid of all those "n"s. I've looked for a macro like > this, but couldn't find it, so I wrote it: > > https://gist.github.com/jamesmacaulay/4993062 > > Using that, I could re-write the above like this: > > (def magnify (iffn pos? inc dec)) > > I can imagine a condfn macro, too: > > (def magnify2 (condfn pos? inc > neg? dec > :else identity) > > Has this kind of conditional function composition been explored much? I > couldn't find anything like it in the standard library, but maybe I wasn't > looking hard enough. > > Cheers, > James > -- -- 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/groups/opt_out.
Re: Like "if", but it composes functions
You don't need a macro for this: user> (defn conditionalize [pred then else] (fn [& args] (if (apply pred args) (apply then args) (apply else args #'user/conditionalize user> ((conditionalize pos? inc dec) 3) 4 user> ((conditionalize pos? inc dec) -3) -4 user> (def magnify (conditionalize pos? inc dec)) #'user/magnify user> (magnify 3) 4 On Tue, Feb 19, 2013 at 9:53 PM, James MacAulay wrote: > Sometimes I find myself writing code like this: > > (defn magnify [n] (if (pos? n) (inc n) (dec n))) > > ...and I want to get rid of all those "n"s. I've looked for a macro like > this, but couldn't find it, so I wrote it: > > https://gist.github.com/jamesmacaulay/4993062 > > Using that, I could re-write the above like this: > > (def magnify (iffn pos? inc dec)) > > I can imagine a condfn macro, too: > > (def magnify2 (condfn pos? inc > neg? dec > :else identity) > > Has this kind of conditional function composition been explored much? I > couldn't find anything like it in the standard library, but maybe I wasn't > looking hard enough. > > Cheers, > James > > -- > -- > 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/groups/opt_out. > > -- Ben Wolfson "Human kind has used its intelligence to vary the flavour of drinks, which may be sweet, aromatic, fermented or spirit-based. ... Family and social life also offer numerous other occasions to consume drinks for pleasure." [Larousse, "Drink" entry] -- -- 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/groups/opt_out.
Like "if", but it composes functions
Sometimes I find myself writing code like this: (defn magnify [n] (if (pos? n) (inc n) (dec n))) ...and I want to get rid of all those "n"s. I've looked for a macro like this, but couldn't find it, so I wrote it: https://gist.github.com/jamesmacaulay/4993062 Using that, I could re-write the above like this: (def magnify (iffn pos? inc dec)) I can imagine a condfn macro, too: (def magnify2 (condfn pos? inc neg? dec :else identity) Has this kind of conditional function composition been explored much? I couldn't find anything like it in the standard library, but maybe I wasn't looking hard enough. Cheers, James -- -- 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/groups/opt_out.
