Re: Like if, but it composes functions
Hello, Why the names fix / to-fix ? 2013/2/20 Alan Malloy a...@malloys.org: 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 ns. 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
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 al...@malloys.org javascript:: 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 ns. 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.comjavascript: 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 javascript: 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 javascript:. 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
2013/2/20 Alan Malloy a...@malloys.org: 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 al...@malloys.org: 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 ns. 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
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
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 jmacau...@gmail.com 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
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 jmacau...@gmail.com 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 ns. 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.
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 ns. 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
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 ns. 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.
