Breaking out of a map type function
Hi All. Still struggling to get my head around Clojure - this is attempt number 4. I wish to process each item in a vector. I know I can use map to do this e.g. (map my-func my-vector). My problem is that I need to be able to break out of the map if my-func returns an error when processing any of the items. I know map isn't what I'm looking for but is there a function or some idiomatic piece of clojure to achieve my aim. cheers Dave -- -- 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: Breaking out of a map type function
Hi Dave, You can use reduce for this job, and have the reducing function return a (reduced retval) when you want to break out. Cheers, Stu On Sun, Nov 24, 2013 at 11:19 AM, David Simmons shortlypor...@gmail.comwrote: Hi All. Still struggling to get my head around Clojure - this is attempt number 4. I wish to process each item in a vector. I know I can use map to do this e.g. (map my-func my-vector). My problem is that I need to be able to break out of the map if my-func returns an error when processing any of the items. I know map isn't what I'm looking for but is there a function or some idiomatic piece of clojure to achieve my aim. cheers Dave -- -- 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: Breaking out of a map type function
Another option is to take-while the values in the sequence are valid, and then map over the ones that are. - James On 24 November 2013 16:50, Stuart Halloway stuart.hallo...@gmail.comwrote: Hi Dave, You can use reduce for this job, and have the reducing function return a (reduced retval) when you want to break out. Cheers, Stu On Sun, Nov 24, 2013 at 11:19 AM, David Simmons shortlypor...@gmail.comwrote: Hi All. Still struggling to get my head around Clojure - this is attempt number 4. I wish to process each item in a vector. I know I can use map to do this e.g. (map my-func my-vector). My problem is that I need to be able to break out of the map if my-func returns an error when processing any of the items. I know map isn't what I'm looking for but is there a function or some idiomatic piece of clojure to achieve my aim. cheers Dave -- -- 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. -- -- 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: Breaking out of a map type function
Hi Stu I understand Reduce but can't quite see how this would work. Don't suppose you'd have a simple example would you? Many thanks Dave -- -- 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: Breaking out of a map type function
On Nov 24, 2013, at 10:19 , David Simmons shortlypor...@gmail.com wrote: I wish to process each item in a vector. I know I can use map to do this e.g. (map my-func my-vector). My problem is that I need to be able to break out of the map if my-func returns an error when processing any of the items. I know map isn't what I'm looking for but is there a function or some idiomatic piece of clojure to achieve my aim. If you only want to break when there's an error, you could use exceptions. Alternatively, if my-func ordinarily doesn't return nil, you could take advantage of map's laziness by having my-func return nil on failure-- then you just stop consuming the output of map when you hit a nil value. -- -- 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: Breaking out of a map type function
@James - I'll take a look at take-while @Michael - I thought using exceptions to break out of a stuff was considered bad practice? cheers Davew -- -- 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: Breaking out of a map type function
Something like: (defn safe-sum [coll] (reduce (fn [s x] (if x (+ x s) (reduced s))) coll)) This will compute the sum until it hits a falsey (i.e. nil or false) value. Alternatively, you could write it: (defn safe-sum [coll] (apply + (take-while identity coll))) - James On 24 November 2013 17:13, David Simmons shortlypor...@gmail.com wrote: Hi Stu I understand Reduce but can't quite see how this would work. Don't suppose you'd have a simple example would you? Many thanks Dave -- -- 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: Breaking out of a map type function
Many thanks 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: Breaking out of a map type function
Hi Dave, Another option is to use the forhttp://clojuredocs.org/clojure_core/clojure.core/formacro's while clause to stop processing as soon as you hit an error. Here's a basic example with a simple my-func that returns a string-based error to give you an idea of how it could look: (defn my-func [n] (cond ( n 4) (str n) :else error)) (for [n [1 2 3 4 5] :let [result (my-func n)] :while (not= result error)] result) Cheers, James On Sunday, November 24, 2013 5:19:49 PM UTC+1, David Simmons wrote: Hi All. Still struggling to get my head around Clojure - this is attempt number 4. I wish to process each item in a vector. I know I can use map to do this e.g. (map my-func my-vector). My problem is that I need to be able to break out of the map if my-func returns an error when processing any of the items. I know map isn't what I'm looking for but is there a function or some idiomatic piece of clojure to achieve my aim. cheers Dave -- -- 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: Breaking out of a map type function
Jernau - that looks perfect. I'll give it a go. cheers Dave -- -- 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.
