Re: I need a vector not a list?
Seems to me that you can make a case for a seq is sort of like an immutable PersistentIterator would be. Iterator - next (get object) seq - first (get object) Iterator - next (mutate to point to next object) seq - next (return new seq whose first is next object) On Tue, Dec 3, 2013 at 2:49 AM, Andy Smith the4thamig...@googlemail.comwrote: Great point... -- -- 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: I need a vector not a list?
Actually, I'd say seqs are very much *unlike* iterators in other languages (Java in particular). Iterators - stateful cursors that conflate iteration with a check for whether more elements exist Seqs - immutable persistent views of a collection that separate iteration from checking for more elements http://clojure.org/sequences On Sunday, December 1, 2013 6:22:57 PM UTC-6, James Reeves wrote: Seqs in Clojure are very much like iterators in other languages. They're an abstraction for navigating a sequential data structure. Also because values in Clojure are immutable, you rarely, if at all, encounter situations where those objects need to be copied. Why would you, when you can just reference the original object, secure in the knowledge that its value cannot change. - James On 1 December 2013 20:15, Andy Smith the4th...@googlemail.comjavascript: wrote: Can a seq be thought of as a kind of a list of pointers to the original vector elements then? If so, then does an operation on a vector, (e.g. reverse), cause clojure to internally generate a seq of pointers to the original vector elements? In other words seqs seem to provide a layer of indirection to avoid the need to copy elements of the original collection? On Saturday, 30 November 2013 21:31:34 UTC, Jim foo.bar wrote: On Sat, 30 Nov 2013 13:15:33 -0800 (PST) Andy Smith the4th...@googlemail.com wrote: but my question is really about the more general case of any function that manipulates a vector e.g. the following also returns a list rather than a vector as desired, In Clojure you rarely have to worry about types. All the data-structures fall under a common set of abstractions and in particular the ISeq interface. Strictly speaking map returns a seq not a list. In fact a lazy seq...this is by design so further operations can be applied lazily later...if you use eager operations like mapv exclusively you lose the ability to aggregate operations without cost. hope that clarifies it... Jim -- -- 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: I need a vector not a list?
Perhaps I should have said that seqs fulfil the same role as iterators do, rather than claiming they're alike :) - James On 2 December 2013 21:42, Alex Miller a...@puredanger.com wrote: Actually, I'd say seqs are very much *unlike* iterators in other languages (Java in particular). Iterators - stateful cursors that conflate iteration with a check for whether more elements exist Seqs - immutable persistent views of a collection that separate iteration from checking for more elements http://clojure.org/sequences On Sunday, December 1, 2013 6:22:57 PM UTC-6, James Reeves wrote: Seqs in Clojure are very much like iterators in other languages. They're an abstraction for navigating a sequential data structure. Also because values in Clojure are immutable, you rarely, if at all, encounter situations where those objects need to be copied. Why would you, when you can just reference the original object, secure in the knowledge that its value cannot change. - James On 1 December 2013 20:15, Andy Smith the4th...@googlemail.com wrote: Can a seq be thought of as a kind of a list of pointers to the original vector elements then? If so, then does an operation on a vector, (e.g. reverse), cause clojure to internally generate a seq of pointers to the original vector elements? In other words seqs seem to provide a layer of indirection to avoid the need to copy elements of the original collection? On Saturday, 30 November 2013 21:31:34 UTC, Jim foo.bar wrote: On Sat, 30 Nov 2013 13:15:33 -0800 (PST) Andy Smith the4th...@googlemail.com wrote: but my question is really about the more general case of any function that manipulates a vector e.g. the following also returns a list rather than a vector as desired, In Clojure you rarely have to worry about types. All the data-structures fall under a common set of abstractions and in particular the ISeq interface. Strictly speaking map returns a seq not a list. In fact a lazy seq...this is by design so further operations can be applied lazily later...if you use eager operations like mapv exclusively you lose the ability to aggregate operations without cost. hope that clarifies it... Jim -- -- 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: I need a vector not a list?
Great point... -- -- 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: I need a vector not a list?
Interesting alternatives. (vec) makes a vector out of a collection, so this is meant to be faster than (apply vector)? Also how does (into []) differ from (vec) in terms of what it does and its performance? On Saturday, 30 November 2013 21:48:10 UTC, Kelker Ryan wrote: Vectors are mostly for speed and maintaining value sequence order. Try this = (vec (reverse [1 2 3])) Not this = (apply vector (reverse [1 2 3])) As an alternative you can do this = (into [] (reverse [1 2 3])) You can always use mapv when calling fun for each coll object. Try this = (mapv #(* 2 %) [1 2 3]) Not this = (apply vector (map (partial * 2) [1 2 3])) 01.12.2013, 06:15, Andy Smith the4th...@googlemail.com javascript:: Hi, I am trying to understand the manipulation of vectors from an efficiency point of view. For example if I want to reverse a vector I can do the following (apply vector (reverse [1 2 3])) My understanding is that reverse will create a new list object (3 2 1) then this will be used to construct a new vector object [3 2 1]. What can I use to construct a new vector directly instead of having the intermediate list object being constructed? I have read about rseq as providing something like a reverse iterator to the same underlying vector, which may be a great solution in this case, but my question is really about the more general case of any function that manipulates a vector e.g. the following also returns a list rather than a vector as desired, (map (partial * 2) [1 2 3]) again forcing me to use apply vector e.g. (apply vector (map (partial * 2) [1 2 3])) Why dont we have a version of map that returns a vector when given a vector? We can do this kind of thing in other languages with templates/generics why not clojure? There is obviously some basic principle/understanding that I am missing here. This kind of thing surely cant be very efficient, can it? Andy -- -- 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 javascript: 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: I need a vector not a list?
Can a seq be thought of as a kind of a list of pointers to the original vector elements then? If so, then does an operation on a vector, (e.g. reverse), cause clojure to internally generate a seq of pointers to the original vector elements? In other words seqs seem to provide a layer of indirection to avoid the need to copy elements of the original collection? On Saturday, 30 November 2013 21:31:34 UTC, Jim foo.bar wrote: On Sat, 30 Nov 2013 13:15:33 -0800 (PST) Andy Smith the4th...@googlemail.com javascript: wrote: but my question is really about the more general case of any function that manipulates a vector e.g. the following also returns a list rather than a vector as desired, In Clojure you rarely have to worry about types. All the data-structures fall under a common set of abstractions and in particular the ISeq interface. Strictly speaking map returns a seq not a list. In fact a lazy seq...this is by design so further operations can be applied lazily later...if you use eager operations like mapv exclusively you lose the ability to aggregate operations without cost. hope that clarifies it... Jim -- -- 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: I need a vector not a list?
Seqs in Clojure are very much like iterators in other languages. They're an abstraction for navigating a sequential data structure. Also because values in Clojure are immutable, you rarely, if at all, encounter situations where those objects need to be copied. Why would you, when you can just reference the original object, secure in the knowledge that its value cannot change. - James On 1 December 2013 20:15, Andy Smith the4thamig...@googlemail.com wrote: Can a seq be thought of as a kind of a list of pointers to the original vector elements then? If so, then does an operation on a vector, (e.g. reverse), cause clojure to internally generate a seq of pointers to the original vector elements? In other words seqs seem to provide a layer of indirection to avoid the need to copy elements of the original collection? On Saturday, 30 November 2013 21:31:34 UTC, Jim foo.bar wrote: On Sat, 30 Nov 2013 13:15:33 -0800 (PST) Andy Smith the4th...@googlemail.com wrote: but my question is really about the more general case of any function that manipulates a vector e.g. the following also returns a list rather than a vector as desired, In Clojure you rarely have to worry about types. All the data-structures fall under a common set of abstractions and in particular the ISeq interface. Strictly speaking map returns a seq not a list. In fact a lazy seq...this is by design so further operations can be applied lazily later...if you use eager operations like mapv exclusively you lose the ability to aggregate operations without cost. hope that clarifies it... Jim -- -- 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: I need a vector not a list?
On Sat, 30 Nov 2013 13:15:33 -0800 (PST) Andy Smith the4thamig...@googlemail.com wrote: Why dont we have a version of map that returns a vector when given a vector? We can do this kind of thing in other languages with templates/generics why not clojure? we do have mapv :) Jim -- -- 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: I need a vector not a list?
On Sat, 30 Nov 2013 13:15:33 -0800 (PST) Andy Smith the4thamig...@googlemail.com wrote: but my question is really about the more general case of any function that manipulates a vector e.g. the following also returns a list rather than a vector as desired, In Clojure you rarely have to worry about types. All the data-structures fall under a common set of abstractions and in particular the ISeq interface. Strictly speaking map returns a seq not a list. In fact a lazy seq...this is by design so further operations can be applied lazily later...if you use eager operations like mapv exclusively you lose the ability to aggregate operations without cost. hope that clarifies it... Jim -- -- 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: I need a vector not a list?
Vectors are mostly for speed and maintaining value sequence order. Try this = (vec (reverse [1 2 3]))Not this = (apply vector (reverse [1 2 3]))As an alternative you can do this = (into [] (reverse [1 2 3]))You can always use mapv when calling fun for each coll object.Try this = (mapv #(* 2 %) [1 2 3])Not this = (apply vector (map (partial * 2) [1 2 3])) 01.12.2013, 06:15, "Andy Smith" the4thamig...@googlemail.com:Hi,I am trying to understand the manipulation of vectors from an efficiency point of view. For example if I want to reverse a vector I can do the following (apply vector (reverse [1 2 3]))My understanding is that reverse will create a new list object (3 2 1) then this will be used to construct a new vector object [3 2 1]. What can I use to construct a new vector directly instead of having the intermediate list object being constructed?I have read about rseq as providing something like a reverse iterator to the same underlying vector, which may be a great solution in this case, but my question is really about the more general case of any function that manipulates a vector e.g. the following also returns a list rather than a vector as desired,(map (partial * 2) [1 2 3]) again forcing me to use apply vector e.g.(apply vector (map (partial * 2) [1 2 3]))Why dont we have a version of map that returns a vector when given a vector? We can do this kind of thing in other languages with templates/generics why not clojure?There is obviously some basic principle/understanding that I am missing here. This kind of thing surely cant be very efficient, can it?Andy -- -- 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.
