The Whiteboard

12:19 AM

@AshleyNunn Well I'd say it was mostly the doctors, but I like to think I helped spiritually

user15026

@Ampt lol well, you guys are collectively keeping me from being completely bored til they cyborgify me tomorrow early so I appreciate it

overexchange

2:23 AM

@MichaelT would you like to answer to this question?

-4

Q: Type checking in dynamic language

from module operator.py we have functional abstraction def concat(a, b): "Same as a + b, for a and b sequences." if not hasattr(a, '__getitem__'): msg = "'%s' object can't be concatenated" % type(a).__name__ raise TypeError(msg) return a + b to perform concatenatio...

as you answered well on chat

overexchange

2:58 AM

sorry the question is on hold, so you can't

user55340

Chat works for such questions.

user55340

(Currently having fun with making a utility in Java that digs into the innards of one object and tries to do its best to clone the fields to the innards of another object... its... yea, reflection... things are going to get interesting real fast...)

overexchange

@MichaelT I am going thru chapter Building abstraction with data from composingprograms.com/pages/21-introduction.html

user55340

Builder is a useful one.

overexchange

what does it mean to say structure info here?

This chapter focuses on data. The techniques we investigate here will allow us to represent and manipulate information about many different domains. Due to the explosive growth of the Internet, a vast amount of structured information is freely available to all of us online, and computation can be applied to a vast range of different problems. Effective use of built-in and user-defined data types are fundamental to data processing applications.

user55340

3:01 AM

        for(Field f : srcFields) {
            try {
                Field dstField = dstClass.getDeclaredField(f.getName());
                boolean state = dstField.isAccessible();
                if(dstField.getType().isAssignableFrom(f.getType())) {

user55340

Oh yea... its going to get fun.

user55340

@overexchange let me tell you about a class that I dealt with the other day. It has about 30 fields in it. Its a bit of a mess. At one time it had 10, and someone made a constructor for it. Then another 5 were added... and another constructor made. This class is an immutable - so no setters. Just constructors.

overexchange

ok

user55340

And so I get to it and I suspect I need to add another field... but its got 5 constructors now, four of which are not used (maybe... maybe not) and the 5th one has 30 parameters. You have to get them all in the right order.

user55340

new Foo(something, something, null, something else, 42, thatthing, null, null, ....)

user55340

3:04 AM

yea, thats easy to follow. You need to change the 23rd parameter.

user55340

So I made an inner builder in there.

user55340

You end up with code that looks like this:

user55340

public class YourTypicalBean {
  private final String foo;
  private String bar, baz;
  private int qux;

  private YourTypicalBean(Builder builder) {
    foo = builder.foo;
    bar = builder.bar;
    baz = builder.baz;
    setQux(builder.qux);
  }

  public int getQux() {
    return qux;
  }

  public static final class Builder {
    private final String foo;
    private String bar;
    private String baz;
    private int qux;

    public Builder(String foo) {
      this.foo = foo;
    }

    public Builder bar(String bar) {

user55340

Something like that...

user55340

And then the calls to it are:

user55340

3:07 AM

Widget = new Widget.Builder(10).setparm1(1).setparm2(3).build();

user55340

But you don't need them to be in any order... or all there even.

user55340

Widget = new Widget.Builder(10).setparm2(3).setparm1(1).build(); // works just as well

user55340

And so, now next time a field is added, instead instead of having a 6th constructor with 31 fields, its a modification to add one 3 line method to the builder and another copy parameter in the private constructor.

user55340

Its a rather useful pattern.

user20683

@MichaelT That's like the first article out of effective java IIRC

user55340

3:15 AM

@WorldEngineer Yep. And its useful and one that is easily recognizable as "this problem there"

overexchange

@MichaelT so constructors are used to initial bind of name(field name) to values and setters are used for re-assignments, correct?

user55340

Often, though conventions of the language differ.

user55340

Java has a 'bean' concept where there is always an empty constructor and setters and getters for every public field.

overexchange

what does it mean to say structured data as I mentioned above?

Is it data coming from flat files or logs that is considered un-structured?

user55340

Logs can be structured data too.

user55340

3:29 AM

192.168.2.20 - - [28/Jul/2006:10:27:10 -0300] "GET /cgi-bin/try/ HTTP/1.0" 200 3395
127.0.0.1 - - [28/Jul/2006:10:22:04 -0300] "GET / HTTP/1.0" 200 2216

user55340

There is structure to that.

overexchange

basically am trying to understand, why the author is saying:

vast amount of structured information is freely available to all of us online, and computation can be applied to a vast range of different problems

composingprograms.com/pages/21-introduction.html

user55340

Quite simply, there's a lot of data out there that is in a machine readable (structured) format such that information can be derived from it and used.

overexchange

ok

user55340

Most recent posts on P.SE via api: api.stackexchange.com/docs/…

user55340

3:34 AM

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