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Re: What is your favorite WC++IETJ?

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  Re: What is your favorite WC++IETJ? Sebastian <news@seyweiler.dyndns.org> - 2015-04-30 14:52 +0200
    Re: What is your favorite WC++IETJ? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-04-30 10:03 -0400
    Re: What is your favorite WC++IETJ? Jerry Stuckle <jstucklex@attglobal.net> - 2015-04-30 12:18 -0400
    Re: What is your favorite WC++IETJ? Robbie Brown <rob@example.com> - 2015-04-30 20:37 +0100

#31628 — Re: What is your favorite WC++IETJ?

Am 30.04.2015 13:44, schrieb Stefan Ram:
>    An WC++IETJ is something »where C++ is easier than Java«.
>
[snip]
> auto const result = new java.util.HashSet< java.lang.Character >();
>
>    Java is so difficult, beginners just can't understand
>    why they have to write everything twice:
>
> final java.util.Set< java.lang.Character >result
> = new java.util.HashSet< java.lang.Character >();
[snip]

Since Java 7, that would be Set<Character> result = new HashSet<>();
and there's really no repetition.

 >
 >    What are your favorite WC++IETJs?

Command line input is more cumbersome with Java, for example it is not 
possible to read an int directly from stdin, you need a Reader (or 
Scanner) and need to convert from String to int yourself. However, 
command line interaction is atypical for most Java applications.

-- Sebastian

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#31631

On 4/30/2015 9:28 AM, Stefan Ram wrote:
> Sebastian <news@seyweiler.dyndns.org> writes:
>> Since Java 7, that would be Set<Character> result = new HashSet<>();
>> and there's really no repetition.
>
>    But this is difficult to remember. One can start from:
>
> HashSet<Character> result = new HashSet<Character>();

     Surely, you meant

	java.util.HashSet<java.lang.Character> result
	    = new java.util.HashSet<java.lang.Character>();

;-)

>    . Now, we want to generalize and omit some specializations
>    (details):
>
> Set<Character> result = new HashSet<>();
>
>    We have to omit the »Hash« on the left, but the »Character«
>    on the right!

     Not a fair criticism, I'd say.  "Hash" is not a specialization,
nor even a "thing" in its own right: It is merely a few characters
extracted from an identifier.  In

	class Settler<T> implements Set<T> {...}

	Set<Character> result = new Settler<>();

... would it be in any sense useful to describe the LHS as being
derived from the RHS by the omission of "tler"?

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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#31634

On 4/30/2015 9:28 AM, Stefan Ram wrote:
<snip>
> 
>   Well, C++ also has its difficulties here. For example, when
>   one wants to read a number, but the user enters a string,
>   one needs to reset the stream in a laborious way, before the
>   read operation can do another attempt at reading a number:
> 
> int x; bool ok; do
> { ok = ::std::cin >> x;
>   else
>   { ::std::cin.clear();
>     ::std::cin.ignore
>     ( ::std::numeric_limits< ::std::streamsize >::max(), '\n' ); }}
> while( !ok );
> 
>   and the meaning of »ok = ::std::cin >> x« is also not
>   very obvious to a beginner.
> 

Which is why it's a bad idea to write code such as this, especially
without any comments.  A code review should reject it (and would on the
projects I have managed).

You can obfuscate your code in almost any language (including Java).
Some make it easier than others.  But that does not mean it's a good
idea.  Unless there is an overwhelming reason otherwise, code should
always be clear and easy to understand - even if it does take a few more
lines to make it so.

-- 
==================
Remove the "x" from my email address
Jerry Stuckle
jstucklex@attglobal.net
==================

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#31635

On 30/04/15 14:58, Stefan Ram wrote:
> ram@zedat.fu-berlin.de (Stefan Ram) writes:
>> . Now, we want to generalize and omit some specializations
>> (details):
>> Set<Character> result = new HashSet<>();
>
>    The general idea of an assignment in Java is:
>
> supertypeVariable = subtypeExpression
>
>    , however in the case of
>
> Set<Character> result = new HashSet<>()
>
>    now, confusingly, the more general designation »<>«
>    appears on the right side, while the more special
>    designation »<Character>« appears on the left side.

The generalization is on the left, the rhs is simply shorthand to stop 
us having to write Set<Character> result = new HashSet<Character>() 
which used to cause howls of protest from even experienced Java 
developers. Try compiling Set<Character> result = new HashSet<Object>()
if the rhs was a generalization we should be able to generalize but we 
can't.

HashSet<>() is not a generalization it is simply shorthand.

The Generalization Set<Character> allows for information hiding, a 
fundamental concept behind the idea of encapsulation.

public Set getFoo(){
    Set x = new HashSet();
    ...
    return x;
}

the implementation of x can be changed without affecting clients of 
getFoo();

Seems perfectly reasonable to me.



-- 
Not floundering ... just fishing

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