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digitalmars.D - key in hash

reply Shammah Chancellor <Shammah_member pathlink.com> writes:
I think the ambiguity of 

key in hash
and
foreach( in int foo; array )

should be removed.  I think "in" is better in the second example.  While I
understand these two contexts 
are _VERY_ different, I was under the impression that Walter was against any
context sensitive syntax at 
all.  (Just look a visual basic for an example of how context sensitive
languages make a mess.)  It also 
makes it that much easier for parsers to do things with the code.

Possibly the key in hash syntax could be replaced with something like this:

hash has key
hash includes key
hash contains key

My personal vote would be with hash has key.


- My two cents
Jul 26 2005
next sibling parent reply "Regan Heath" <regan netwin.co.nz> writes:
On Wed, 27 Jul 2005 05:53:16 +0000 (UTC), Shammah Chancellor  
<Shammah_member pathlink.com> wrote:

 I think the ambiguity of

 key in hash
 and
 foreach( in int foo; array )

 should be removed.  I think "in" is better in the second example.  While  
 I
 understand these two contexts
 are _VERY_ different, I was under the impression that Walter was against  
 any
 context sensitive syntax at
 all.  (Just look a visual basic for an example of how context sensitive
 languages make a mess.)  It also
 makes it that much easier for parsers to do things with the code.

 Possibly the key in hash syntax could be replaced with something like  
 this:

 hash has key
 hash includes key
 hash contains key

 My personal vote would be with hash has key.


I prefer "contains" and I prefer a method format, eg.

if (hash.contains(key)) //true/false
if (hash.contains(key,value)) //true/false, sets value on true

This allows a check and get with a single lookup and no pointers if  
desired (the 2nd form)

Regan
Jul 26 2005
next sibling parent "Craig Black" <cblack ara.com> writes:
I agree, 'contains' is better than 'in'.

-Craig

"Regan Heath" <regan netwin.co.nz> wrote in message 
news:opsuj5i2iy23k2f5 nrage.netwin.co.nz...

 On Wed, 27 Jul 2005 05:53:16 +0000 (UTC), Shammah Chancellor 
 <Shammah_member pathlink.com> wrote:

 I think the ambiguity of

 key in hash
 and
 foreach( in int foo; array )

 should be removed.  I think "in" is better in the second example.  While 
 I
 understand these two contexts
 are _VERY_ different, I was under the impression that Walter was against 
 any
 context sensitive syntax at
 all.  (Just look a visual basic for an example of how context sensitive
 languages make a mess.)  It also
 makes it that much easier for parsers to do things with the code.

 Possibly the key in hash syntax could be replaced with something like 
 this:

 hash has key
 hash includes key
 hash contains key

 My personal vote would be with hash has key.


 I prefer "contains" and I prefer a method format, eg.

 if (hash.contains(key)) //true/false
 if (hash.contains(key,value)) //true/false, sets value on true

 This allows a check and get with a single lookup and no pointers if 
 desired (the 2nd form)

 Regan
Jul 27 2005
prev sibling parent Shammah Chancellor <Shammah_member pathlink.com> writes:
In article <opsuj5i2iy23k2f5 nrage.netwin.co.nz>, Regan Heath says...

On Wed, 27 Jul 2005 05:53:16 +0000 (UTC), Shammah Chancellor  
<Shammah_member pathlink.com> wrote:

 I think the ambiguity of

 key in hash
 and
 foreach( in int foo; array )

 should be removed.  I think "in" is better in the second example.  While  
 I
 understand these two contexts
 are _VERY_ different, I was under the impression that Walter was against  
 any
 context sensitive syntax at
 all.  (Just look a visual basic for an example of how context sensitive
 languages make a mess.)  It also
 makes it that much easier for parsers to do things with the code.

 Possibly the key in hash syntax could be replaced with something like  
 this:

 hash has key
 hash includes key
 hash contains key

 My personal vote would be with hash has key.


I prefer "contains" and I prefer a method format, eg.

if (hash.contains(key)) //true/false
if (hash.contains(key,value)) //true/false, sets value on true

This allows a check and get with a single lookup and no pointers if  
desired (the 2nd form)

Regan



Ah much better.  Just get rid of special operators alltogether.  Plus that
second example clears up some problems with testing hashes before you use their
values when they're classes.

Then you can easily do this:

if( hash.contains( key, value ) && value ) value.foo

I think that should be called get() though as before.  Contains leads you to
believe that it contains that key-value pair.

And if we're going to start adding properties on AA's like
remove and .add why not go the rest of the way and add contains and get?

-Sha
Jul 27 2005
prev sibling next sibling parent "Ben Hinkle" <ben.hinkle gmail.com> writes:
"Shammah Chancellor" <Shammah_member pathlink.com> wrote in message 
news:dc77gc$228i$1 digitaldaemon.com...

I think the ambiguity of

 key in hash
 and
 foreach( in int foo; array )

 should be removed.  I think "in" is better in the second example.  While I
 understand these two contexts
 are _VERY_ different, I was under the impression that Walter was against 
 any
 context sensitive syntax at
 all.  (Just look a visual basic for an example of how context sensitive
 languages make a mess.)  It also
 makes it that much easier for parsers to do things with the code.


By "context sensitive" Walter (I believe) means that the semantics of 
symbols - for example when a C++ parser sees  a < b it needs to know if a is 
a template about to be instantiated or if it < is less-than. In D the uses 
of 'in' never need to know any information about the surrounding symbols to 
do its job. In a param list it means 'in/out/inout' and in an expression it 
means 'hash in'.
I'm not sure what you mean by making things easier for parsers to do things 
to code - do you have an example in mind?

As for changing 'in' to something else I don't have a strong opinion - it 
would make it easier for MinTL to mimic builtin AA's since we don't have any 
opIn for 'in' overloading so unless opIn is added I agree 'in' should change 
and Regan's suggestion looks like a good way to go. In any case the bool 
contains(key,out value) would be useful no matter what happened to 'in'.
Jul 27 2005
prev sibling next sibling parent reply AJG <AJG_member pathlink.com> writes:
I really don't mind "in", but if it's going to be changed, my vote is for "has".
Keep it nice and short.

In addition, let's not forget about the negative version(s)...









Cheers,
--AJG.


In article <dc77gc$228i$1 digitaldaemon.com>, Shammah Chancellor says...

I think the ambiguity of 

key in hash
and
foreach( in int foo; array )

should be removed.  I think "in" is better in the second example.  While I
understand these two contexts 
are _VERY_ different, I was under the impression that Walter was against any
context sensitive syntax at 
all.  (Just look a visual basic for an example of how context sensitive
languages make a mess.)  It also 
makes it that much easier for parsers to do things with the code.

Possibly the key in hash syntax could be replaced with something like this:

hash has key
hash includes key
hash contains key

My personal vote would be with hash has key.


- My two cents
Jul 27 2005
parent =?utf-8?B?RGF3aWQgQ2nEmcW8YXJraWV3aWN6?= <araelx gmail.com> writes:
On Wed, 27 Jul 2005 17:51:49 +0200, AJG <AJG_member pathlink.com> wrote:

 In addition, let's not forget about the negative version(s)...






Yes. I'm waiting for "!in" too.







Bleh ...
-- 
Dawid Ciężarkiewicz
Jul 27 2005
prev sibling next sibling parent "Charles" <noone nowhere.com> writes:
in has three uses , DBC , key in hash , and a modifier for parameters.

I agree with Regan, 'contains' gets my vote , and unless it also works for
arrays , Id argue the method syntax.

Charlie

"Shammah Chancellor" <Shammah_member pathlink.com> wrote in message
news:dc77gc$228i$1 digitaldaemon.com...

 I think the ambiguity of

 key in hash
 and
 foreach( in int foo; array )

 should be removed.  I think "in" is better in the second example.  While I
 understand these two contexts
 are _VERY_ different, I was under the impression that Walter was against


any

 context sensitive syntax at
 all.  (Just look a visual basic for an example of how context sensitive
 languages make a mess.)  It also
 makes it that much easier for parsers to do things with the code.

 Possibly the key in hash syntax could be replaced with something like


this:

 hash has key
 hash includes key
 hash contains key

 My personal vote would be with hash has key.


 - My two cents
Jul 27 2005
prev sibling parent Manfred Nowak <svv1999 hotmail.com> writes:
Shammah Chancellor <Shammah_member pathlink.com> wrote:


 I think the ambiguity of 
 
 key in hash
 and
 foreach( in int foo; array )


[...]

This is not an ambiguity in any way.

For example: parentheses are spread over the grammar at several 
places but introduce an ambiguity only at a very special construct:

http://www.digitalmars.com/drn-bin/wwwnews?digitalmars.D.bugs/3847

-manfred
Jul 27 2005