Re: Duplicate key bug in hash-maps
Easy to explain - absolutely, consistent - mm, not really...
I found this new behavior a bit confusing, imo it breaks principle of
least surprise.
This feature is uncommon in dynamic languages (even Scala allows
duplicate keys - Set('a,'a)/Map('a->1,'a->1)).
Also, from the practical point of view, when prototyping:
- repl: user>(some-fn #{1 ...}) ;just experiment here
- file: #{"http://xyz"; ...} ;bunch of statistical data
In both cases occasional duplicate is not critical.
However, one will be forced to spend extra time on input double-check
and/or deal with error message(s).
-anton
On Jun 25, 5:31 pm, Stuart Halloway wrote:
> Duplicate keys in maps/sets are disallowed in literals and factory functions,
> where data is generally literal & inline and therefore likely represents
> coder error:
>
> ; all disallowed
> #{:a :a}
> {:a 1 :a 2}
> (hash-map :a 1 :a 2)
> (hash-set :a :a)
>
> They are allowed in other contexts, where the data could come from anywhere:
>
> ; dumb, but these forms not generally called with a literal
> (set [:a :a])
> (into #{} [:a :a])
>
> I find this behavior consistent and easy to explain, but I was involved in
> the design conversation so maybe I have participant blindness. :-)
>
> Stu
>
>
>
> > On Fri, 25 Jun 2010 15:36:31 +0200
> > Michael Wood wrote:
>
> >> On 25 June 2010 12:27, Tim Robinson wrote:
> >>> I tried Clojure via Githhub today.
>
> >>> Anyone notice this bug that hadn't existed in Version 1.1
>
> >>> user=> #{:item1 {:a "A" :b "B"} :item2 {:a "A" :b "B"}}
> >>> java.lang.IllegalArgumentException: Duplicate key: {:a "A", :b "B"}
>
> >> You're trying to put duplicate values into a set.
>
> > So? Most places, putting a value that's already in a set into the set
> > is a nop. Even in clojure that exhibits the above behavior:
>
> > user=> #{:a :a}
> > java.lang.IllegalArgumentException: Duplicate key: :a
> > user=> (set [:a :a])
> > #{:a}
> > user=> (conj #{:a} :a)
> > #{:a}
> > user=>
>
> > Apparently, duplicate keys in sets are only disallowed in set
> > literals. Arguably, that must be a mistake on the users part, but
> > it sure seems to clash with the behavior of sets elsewhere.
>
> > > --
> > Mike Meyer
> > http://www.mired.org/consulting.html
> > Independent Network/Unix/Perforce consultant, email for more information.
>
> > O< ascii ribbon campaign - stop html mail -www.asciiribbon.org
>
> > --
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Re: Duplicate key bug in hash-maps
I agree that duplicate keys in literals are probably a coder error but
IMO this deserves some kind of compiler warning rather than an error.
You're going to get into lots of sticky situations otherwise that only
confuse people if the semantics are different between literals and
other usage. Simple is good.
On Jun 25, 3:31 pm, Stuart Halloway wrote:
> Duplicate keys in maps/sets are disallowed in literals and factory functions,
> where data is generally literal & inline and therefore likely represents
> coder error:
>
> ; all disallowed
> #{:a :a}
> {:a 1 :a 2}
> (hash-map :a 1 :a 2)
> (hash-set :a :a)
>
> They are allowed in other contexts, where the data could come from anywhere:
>
> ; dumb, but these forms not generally called with a literal
> (set [:a :a])
> (into #{} [:a :a])
>
> I find this behavior consistent and easy to explain, but I was involved in
> the design conversation so maybe I have participant blindness. :-)
>
> Stu
>
>
>
> > On Fri, 25 Jun 2010 15:36:31 +0200
> > Michael Wood wrote:
>
> >> On 25 June 2010 12:27, Tim Robinson wrote:
> >>> I tried Clojure via Githhub today.
>
> >>> Anyone notice this bug that hadn't existed in Version 1.1
>
> >>> user=> #{:item1 {:a "A" :b "B"} :item2 {:a "A" :b "B"}}
> >>> java.lang.IllegalArgumentException: Duplicate key: {:a "A", :b "B"}
>
> >> You're trying to put duplicate values into a set.
>
> > So? Most places, putting a value that's already in a set into the set
> > is a nop. Even in clojure that exhibits the above behavior:
>
> > user=> #{:a :a}
> > java.lang.IllegalArgumentException: Duplicate key: :a
> > user=> (set [:a :a])
> > #{:a}
> > user=> (conj #{:a} :a)
> > #{:a}
> > user=>
>
> > Apparently, duplicate keys in sets are only disallowed in set
> > literals. Arguably, that must be a mistake on the users part, but
> > it sure seems to clash with the behavior of sets elsewhere.
>
> > > --
> > Mike Meyer
> > http://www.mired.org/consulting.html
> > Independent Network/Unix/Perforce consultant, email for more information.
>
> > O< ascii ribbon campaign - stop html mail -www.asciiribbon.org
>
> > --
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Re: Duplicate key bug in hash-maps
Can I change the title to:
"Duplicate key error handling feature in hash-sets" ?
I was using the '#' thinking it was short for a hash-map, rather than
a hash-set.
Clojure has more data structures available than I'm used to working
with.
So thanks for the error handling.
Tim
On Jun 25, 9:37 am, Stuart Halloway wrote:
> I think there are two important considerations in favor of how it works now:
>
> (1) The "common case" presumptions (which admittedly may need to be learned).
>
> (2) The need for both flavors. If there wasn't a flavor that rejected
> duplicate keys, somebody would surely ask for it.
>
> Add to these considerations the names of the functions already in play, and
> you get the implementation you see.
>
>
>
> > On Fri, 25 Jun 2010 10:31:57 -0400
> > Stuart Halloway wrote:
>
> >> Duplicate keys in maps/sets are disallowed in literals and factory
> >> functions, where data is generally literal & inline and therefore likely
> >> represents coder error:
>
> >> ; all disallowed
> >> #{:a :a}
> >> {:a 1 :a 2}
> >> (hash-map :a 1 :a 2)
> >> (hash-set :a :a)
>
> > Maps I can see being an error - you lose data in the process.
>
> > However, since you can plug variables of unknown provenance into
> > either the constructor or the literal, that's liable to create a nasty
> > surprise for someone at some point.
>
> > user=> (def a :a)
> > #'user/b
> > user=> (def b :a)
> > #'user/b
> > user=> (hash-set a b)
> > java.lang.IllegalArgumentException: Duplicate key: :a (NO_SOURCE_FILE:6)
> > user=> #{a b}
> > java.lang.IllegalArgumentException: Duplicate key: :a (NO_SOURCE_FILE:0)
> > user=>
>
> >> They are allowed in other contexts, where the data could come from
> >> anywhere:
>
> > It could come from anywhere in the two "forbidden" contexts as well.
>
> >> ; dumb, but these forms not generally called with a literal
> >> (set [:a :a])
> >> (into #{} [:a :a])
>
> >> I find this behavior consistent and easy to explain, but I was involved in
> >> the design conversation so maybe I have participant blindness. :-)
>
> > My initial reaction was "that's a bit odd, but probably a good idea."
> > However, given that I can use variables inside the literal and
> > constructor, I'm leaning the other way.
>
> > Or is (set [a b c]) idiomatic usage in this case, and (hash-set a b c)
> > or #{a b c} to be avoided?
>
> > > --
> > Mike Meyer
> > http://www.mired.org/consulting.html
> > Independent Network/Unix/Perforce consultant, email for more information.
>
> > O< ascii ribbon campaign - stop html mail -www.asciiribbon.org
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Re: Duplicate key bug in hash-maps
On Fri, 25 Jun 2010 11:37:32 -0400 Stuart Halloway wrote: > (2) The need for both flavors. If there wasn't a flavor that rejected > duplicate keys, somebody would surely ask for it. I guess it makes as much sense as anything, given that you don't want to get into -unique or some such. But it does leave me wondering where the duplicate-rejecting version of into is :-). http://www.mired.org/consulting.html Independent Network/Unix/Perforce consultant, email for more information. O< ascii ribbon campaign - stop html mail - www.asciiribbon.org -- 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: Duplicate key bug in hash-maps
I think there are two important considerations in favor of how it works now:
(1) The "common case" presumptions (which admittedly may need to be learned).
(2) The need for both flavors. If there wasn't a flavor that rejected duplicate
keys, somebody would surely ask for it.
Add to these considerations the names of the functions already in play, and you
get the implementation you see.
> On Fri, 25 Jun 2010 10:31:57 -0400
> Stuart Halloway wrote:
>
>> Duplicate keys in maps/sets are disallowed in literals and factory
>> functions, where data is generally literal & inline and therefore likely
>> represents coder error:
>>
>> ; all disallowed
>> #{:a :a}
>> {:a 1 :a 2}
>> (hash-map :a 1 :a 2)
>> (hash-set :a :a)
>
> Maps I can see being an error - you lose data in the process.
>
> However, since you can plug variables of unknown provenance into
> either the constructor or the literal, that's liable to create a nasty
> surprise for someone at some point.
>
> user=> (def a :a)
> #'user/b
> user=> (def b :a)
> #'user/b
> user=> (hash-set a b)
> java.lang.IllegalArgumentException: Duplicate key: :a (NO_SOURCE_FILE:6)
> user=> #{a b}
> java.lang.IllegalArgumentException: Duplicate key: :a (NO_SOURCE_FILE:0)
> user=>
>
>
>> They are allowed in other contexts, where the data could come from anywhere:
>
> It could come from anywhere in the two "forbidden" contexts as well.
>
>> ; dumb, but these forms not generally called with a literal
>> (set [:a :a])
>> (into #{} [:a :a])
>>
>> I find this behavior consistent and easy to explain, but I was involved in
>> the design conversation so maybe I have participant blindness. :-)
>
> My initial reaction was "that's a bit odd, but probably a good idea."
> However, given that I can use variables inside the literal and
> constructor, I'm leaning the other way.
>
> Or is (set [a b c]) idiomatic usage in this case, and (hash-set a b c)
> or #{a b c} to be avoided?
>
>--
> Mike Meyerhttp://www.mired.org/consulting.html
> Independent Network/Unix/Perforce consultant, email for more information.
>
> O< ascii ribbon campaign - stop html mail - www.asciiribbon.org
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Re: Duplicate key bug in hash-maps
On Fri, 25 Jun 2010 10:31:57 -0400
Stuart Halloway wrote:
> Duplicate keys in maps/sets are disallowed in literals and factory functions,
> where data is generally literal & inline and therefore likely represents
> coder error:
>
> ; all disallowed
> #{:a :a}
> {:a 1 :a 2}
> (hash-map :a 1 :a 2)
> (hash-set :a :a)
Maps I can see being an error - you lose data in the process.
However, since you can plug variables of unknown provenance into
either the constructor or the literal, that's liable to create a nasty
surprise for someone at some point.
user=> (def a :a)
#'user/b
user=> (def b :a)
#'user/b
user=> (hash-set a b)
java.lang.IllegalArgumentException: Duplicate key: :a (NO_SOURCE_FILE:6)
user=> #{a b}
java.lang.IllegalArgumentException: Duplicate key: :a (NO_SOURCE_FILE:0)
user=>
> They are allowed in other contexts, where the data could come from anywhere:
It could come from anywhere in the two "forbidden" contexts as well.
> ; dumb, but these forms not generally called with a literal
> (set [:a :a])
> (into #{} [:a :a])
>
> I find this behavior consistent and easy to explain, but I was involved in
> the design conversation so maybe I have participant blindness. :-)
My initial reaction was "that's a bit odd, but probably a good idea."
However, given that I can use variables inside the literal and
constructor, I'm leaning the other way.
Or is (set [a b c]) idiomatic usage in this case, and (hash-set a b c)
or #{a b c} to be avoided?
http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.
O< ascii ribbon campaign - stop html mail - www.asciiribbon.org
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Re: Duplicate key bug in hash-maps
Duplicate keys in maps/sets are disallowed in literals and factory functions,
where data is generally literal & inline and therefore likely represents coder
error:
; all disallowed
#{:a :a}
{:a 1 :a 2}
(hash-map :a 1 :a 2)
(hash-set :a :a)
They are allowed in other contexts, where the data could come from anywhere:
; dumb, but these forms not generally called with a literal
(set [:a :a])
(into #{} [:a :a])
I find this behavior consistent and easy to explain, but I was involved in the
design conversation so maybe I have participant blindness. :-)
Stu
> On Fri, 25 Jun 2010 15:36:31 +0200
> Michael Wood wrote:
>
>> On 25 June 2010 12:27, Tim Robinson wrote:
>>> I tried Clojure via Githhub today.
>>>
>>> Anyone notice this bug that hadn't existed in Version 1.1
>>>
>>> user=> #{:item1 {:a "A" :b "B"} :item2 {:a "A" :b "B"}}
>>> java.lang.IllegalArgumentException: Duplicate key: {:a "A", :b "B"}
>>
>> You're trying to put duplicate values into a set.
>
> So? Most places, putting a value that's already in a set into the set
> is a nop. Even in clojure that exhibits the above behavior:
>
> user=> #{:a :a}
> java.lang.IllegalArgumentException: Duplicate key: :a
> user=> (set [:a :a])
> #{:a}
> user=> (conj #{:a} :a)
> #{:a}
> user=>
>
> Apparently, duplicate keys in sets are only disallowed in set
> literals. Arguably, that must be a mistake on the users part, but
> it sure seems to clash with the behavior of sets elsewhere.
>
> --
> Mike Meyerhttp://www.mired.org/consulting.html
> Independent Network/Unix/Perforce consultant, email for more information.
>
> O< ascii ribbon campaign - stop html mail - www.asciiribbon.org
>
> --
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Re: Duplicate key bug in hash-maps
> > > Apparently, duplicate keys in sets are only disallowed in set > literals. Arguably, that must be a mistake on the users part, but > it sure seems to clash with the behavior of sets elsewhere. > > Why would you ever want to write a duplicate in a set literal? -- 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: Duplicate key bug in hash-maps
On Fri, 25 Jun 2010 15:36:31 +0200
Michael Wood wrote:
> On 25 June 2010 12:27, Tim Robinson wrote:
> > I tried Clojure via Githhub today.
> >
> > Anyone notice this bug that hadn't existed in Version 1.1
> >
> > user=> #{:item1 {:a "A" :b "B"} :item2 {:a "A" :b "B"}}
> > java.lang.IllegalArgumentException: Duplicate key: {:a "A", :b "B"}
>
> You're trying to put duplicate values into a set.
So? Most places, putting a value that's already in a set into the set
is a nop. Even in clojure that exhibits the above behavior:
user=> #{:a :a}
java.lang.IllegalArgumentException: Duplicate key: :a
user=> (set [:a :a])
#{:a}
user=> (conj #{:a} :a)
#{:a}
user=>
Apparently, duplicate keys in sets are only disallowed in set
literals. Arguably, that must be a mistake on the users part, but
it sure seems to clash with the behavior of sets elsewhere.
http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.
O< ascii ribbon campaign - stop html mail - www.asciiribbon.org
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Re: Duplicate key bug in hash-maps
On 25 June 2010 12:27, Tim Robinson wrote:
> I tried Clojure via Githhub today.
>
> Anyone notice this bug that hadn't existed in Version 1.1
>
> user=> #{:item1 {:a "A" :b "B"} :item2 {:a "A" :b "B"}}
> java.lang.IllegalArgumentException: Duplicate key: {:a "A", :b "B"}
You're trying to put duplicate values into a set.
Did you mean this instead?
user=> (def x {:item1 {:a "A" :b "B"} :item2 {:a "A" :b "B"}})
#'user/x
user=> (:item1 x)
{:a "A", :b "B"}
user=> (:item2 x)
{:a "A", :b "B"}
user=>
--
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Re: Duplicate key bug in hash-maps
Duplicate key prevention is a feature added in commit
c733148ba0fb3ff7bbab133f5375422972e62d08.
Stu
> I tried Clojure via Githhub today.
>
> Anyone notice this bug that hadn't existed in Version 1.1
>
> user=> #{:item1 {:a "A" :b "B"} :item2 {:a "A" :b "B"}}
> java.lang.IllegalArgumentException: Duplicate key: {:a "A", :b "B"}
>
> Tim
>
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Duplicate key bug in hash-maps
I tried Clojure via Githhub today.
Anyone notice this bug that hadn't existed in Version 1.1
user=> #{:item1 {:a "A" :b "B"} :item2 {:a "A" :b "B"}}
java.lang.IllegalArgumentException: Duplicate key: {:a "A", :b "B"}
Tim
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