Re: Key order of literal maps
Thanks for the responses. On 3 May 2011 17:39, Steve Miner wrote: > > On May 3, 2011, at 7:08 AM, David Jagoe wrote: > > For your specific purpose, I would be careful about using a map as an > "entity" specification. If the order is significant, a vector of field > specifiers would be better. Instead of taking a map as the second argument > to defentity, you could make it variadic like (defmacro defentity [ent & > specs] ...). Yes, that looks like the solution. Thanks again. David > > -- > 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 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
Re: Key order of literal maps
On May 3, 2011, at 7:08 AM, David Jagoe wrote: > Can I rely on (keys some-literal-map) always returning the keys in the > order they were defined in the literal map? In general, the key order is not guaranteed, but an array-map will maintain the insertion order of the keys. Use the array-map function to create one. There's a bit more info here: http://clojuredocs.org/clojure_core/clojure.core/array-map > An array-map maintains the insertion order of the keys. Look up is linear, > which is not a problem for small maps (say less than 10 keys). If your map is > large, you should use hash-map instead. > > When you assoc onto an existing array-map, the result is a new array-map with > the new key as the first key. The rest of the keys are in the same order as > the original. Functions such as seq and keys will respect the key order. > > Note that assoc will decide to return a hash-map if the result is too big to > be efficient. For your specific purpose, I would be careful about using a map as an "entity" specification. If the order is significant, a vector of field specifiers would be better. Instead of taking a map as the second argument to defentity, you could make it variadic like (defmacro defentity [ent & specs] ...). -- 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
Re: Key order of literal maps
Keys from literal maps aren't sorted; you need a sorted map.
user=> (keys {:z 1 :f 2 :a 0})
(:z :a :f)
user=> (keys (sorted-map :z 1 :f 2 :a 0))
(:a :f :z)
On May 3, 4:08 am, David Jagoe wrote:
> Hey everyone,
>
> I'm busy implementing a macro whose usage looks like this:
>
> (defentity Person
> {:name {:type String :validator name-validator}
> :id-number {:type String :validator id-number-validator}
> :height {:type Float :default 0.0}
> :weight {:type Float :default 0.0}
> :bmi {:type Float :internal true}})
>
> The macro generates a defrecord like so:
>
> (defrecord Person [name id-number height weight bmi])
>
> Which can later be used in the application like this:
>
> (Person. "David" "123" 1 2 3)
>
> Obviously the argument order is important. So my question is:
>
> Can I rely on (keys some-literal-map) always returning the keys in the
> order they were defined in the literal map? In my experiment, a map
> literal will create a PersistentArrayMap which I understand has sorted
> keys. Can someone confirm that this is reliable (e.g. across
> implementations?)
>
> Thanks!
> David
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Key order of literal maps
Hey everyone,
I'm busy implementing a macro whose usage looks like this:
(defentity Person
{:name {:type String :validator name-validator}
:id-number {:type String :validator id-number-validator}
:height{:type Float :default 0.0}
:weight{:type Float :default 0.0}
:bmi {:type Float :internal true}})
The macro generates a defrecord like so:
(defrecord Person [name id-number height weight bmi])
Which can later be used in the application like this:
(Person. "David" "123" 1 2 3)
Obviously the argument order is important. So my question is:
Can I rely on (keys some-literal-map) always returning the keys in the
order they were defined in the literal map? In my experiment, a map
literal will create a PersistentArrayMap which I understand has sorted
keys. Can someone confirm that this is reliable (e.g. across
implementations?)
Thanks!
David
--
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