Mark Engelberg wrote:
> 2009/11/9 Tiago Antão <[email protected]>:
>> What is the rationale for even? and contains? having different
>> behaviors for the exact same error (ie, one throws the other works
>> fine and just returns false on a type error)?
> I imagine the rationale is efficiency.
Here's the function from clojure/lang/RT.java:
static public Object contains(Object coll, Object key){
if(coll == null)
return F;
else if(coll instanceof Associative)
return ((Associative) coll).containsKey(key) ? T : F;
else if(coll instanceof IPersistentSet)
return ((IPersistentSet) coll).contains(key) ? T : F;
else if(coll instanceof Map) {
Map m = (Map) coll;
return m.containsKey(key) ? T : F;
}
else if(key instanceof Number && (coll instanceof String ||
coll.getClass().isArray())) {
int n = ((Number) key).intValue();
return n >= 0 && n < count(coll);
}
return F;
}
That last return could be changed to a throw and it wouldn't make things
any slower (in the non-error case). Note that 'get' always behaves the
same way, so I guess it's probably intentional for associative lookups,
I can't see why though.
(get 3 3)
=> nil
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