The 2nd Monitor

Mat's Mug

10:00 PM

basically it's up to the compiler to evaluate/infer it

Phrancis

Makes sense

I notice there are a lot of types in C#, it gets a bit confusing deciding which is best to use

Quill

I should swap over to ANTLR or jison soon, I wrote my own tokenizer but it's easily the worst code I've ever written

Mat's Mug

there's a few type aliases in C#, the types themselves are defined in the .net framework

Phrancis

For instance ulong vs. UInt64

Mat's Mug

ulong being a C# alias for the .net UInt64

int being a C# alias for the .net Int32

string being a C# alias for the .net String

Phrancis

10:02 PM

Hm, do they basically have all the same functions/methods?

Mat's Mug

the aliases compile to the .net types

N3buchadnezzar

Latex looks so nice

Mat's Mug

i.e. they're exactly the same thing

@N3buchadnezzar feel free to share your clothing preferences in the Nth Monitor ;-)

(kidding)

Phrancis

So if I can do Math.Sqrt(int) I can also do Math.Sqrt(Int32)?

N3buchadnezzar

@Mat'sMug Whips mat

Mat's Mug

10:04 PM

LaTex I believe :)

N3buchadnezzar

How is it going?

Mat's Mug

lol

N3buchadnezzar

\$\Latex\$

Dammit :p

Mat's Mug

aka MathJax

Phrancis

\$LaTeX\$

Sure looks nice for typography etc.

Duga

10:06 PM

@nethken you may be looking for codereview.stackexchange.com Code Review Stack Exchange where people will review your code, this seems to be what you're after.... — Martin 31 secs ago

Mat's Mug

@Phrancis you'd do Math.Sqrt(42) and that 42 is a System.Int32 as far as the compiled/running code is concerned.

N3buchadnezzar

Really like how LaTex can import .py files directly from source.

Quill

@Mat'sMug do the C# aliases have additional instance methods?

Mat's Mug

nope

Phrancis

Makes sense, so in reality you can just use whichever of the alias or .NET type and it makes no difference whatsoever

Mat's Mug

10:07 PM

except constantly switching between the two makes your code pretty ugly

rule of thumb, use the language aliases whenever possible, and stick to them.

Phrancis

@Mat'sMug I can imagine

Quill

I think I've got into an argument with every programmer at my workplace about String and string differences

N3buchadnezzar

@Quill You say what mate?! You wanna foight?

Mat's Mug

@Quill and who won?

Phrancis

One starts with a capital letter and the other doesn't?

Quill

10:09 PM

@Mat'sMug the code reviewers always win ;-)

N3buchadnezzar

Not always :(

Spagetthi sometimes wins

Phrancis

Sorry for all the questions, C# is kind of new to me and being used to Java's very strict typing syntax...

Quill

@Phrancis questions are good :)

Mat's Mug

I use string everywhere. some argue that when it stands for a type, it should be string, and when it's used as a static class for its static methods, it should be String because "it makes it more obvious that String is a reference type". I call BS. If you don't know that System.String is a reference type, you have homework to do.

N3buchadnezzar

goes to the homework cup of shame

Quill

10:11 PM

@Mat'sMug hahaha can you do our performance reviews here

Phrancis

BRB Googling "what is a reference type"

Mat's Mug

shortly put, a reference type is a class, and a value type is a struct.

Phrancis

Oh so value types are like the primitive types, while reference types are pointers to objects... right?

Quill

@Phrancis yup

Mat's Mug

waits for the "reference types are stored on the heap, value types are stored on the stack" comment

Quill

10:13 PM

similar to JavaScript's boxing; wrap the primitive in a pretty box with extra features

N3buchadnezzar

reference types are stored on the heap, value types are stored on the stack

Phrancis

I've used Java's int vs. Integer types so that concept is at least familiar

Mat's Mug

boxing is when you take a value type and "box" it in a reference type. the cost of this is "unboxing"

@Phrancis that's outright confusing imo

Phrancis

Integer have methods since they are objects, while int are just that, a number

Mat's Mug

in C# an int is a System.Int32 no matter what, and it has value type semantics no matter what, and the members and extension methods of a System.Int32 no matter what.

object foo;
foo = 42; // you've just boxed an integer

int bar;
bar = (int)foo; // you've just unboxed a boxed integer

Phrancis

10:19 PM

Object foo;
foo = 42;
System.out.println(foo.getClass()); // java.lang.Integer
System.out.prinln((int)foo.getClass()); //Main.java:6: error: incompatible types: Class<CAP#1> cannot be converted to int

Mat's Mug

@Phrancis wait till you get to C# generics.

@Phrancis or Integer foo; right?

Quill

@Mat'sMug I tried generics yesterday and it was.... different.....

Phrancis

@Mat'sMug yep, and I just added what happens if you try to cast an Integer to primitive int

Mat's Mug

@Quill C# generics don't incur boxing/unboxing penalty.

Phrancis

In that sense, C# does seem a lot more convenient than Java

Mat's Mug

10:24 PM

TTQW

Quill

Yeah... I really need to write more C#

Dan Pantry

@Phrancis Another nice (depending on your outlook) thing about C# is that in C# generic types are not "erased" at runtime

in Java generic types are only for the benefit of type checking which means you can't use reflection to determine what generic type was used at runtime

Which is.. cumbersome when it comes to mocking in tests

in C# generic types are preserved at runtime

The upshot of that being that there has to be more information encoded in a C# binary so it may be larger

Phrancis

So in C# a generic remains generic up until it's assigned/used, vs. in Java it's only generic before compiling?

Dan Pantry

a type remains generic information in C# forever

In Java that generic information is erased after compilation

Mat's Mug

@DanPantry which is only a big deal if you're distributing your app on floppies

Phrancis

10:33 PM

lol floppies

Dan Pantry

So in C#, a List<int> is a List<int> which isn't a List<float> at runtime.

But in Java, technically speaking, a List<Integer> and a List<Float> are both List at runtime

There are a few situations where C#'s version is more useful

Mat's Mug

That sounds nasty

Anyway gtg now - later!

Phrancis

Later!

Dan Pantry

Cya @Mat'sMug

OOTH, you could also argue that preserving type information at runtime breaks static typing as it allows you to create unpredictable types at runtime, and so Java does it right

¯\_(ツ)_/¯

Mat's Mug

@DanPantry unpredictable as in proxy types and mocks? Heck I'll take it!

Quill

10:45 PM

that was a fast drive

Phrancis

uhhh

WTF does that even mean

> CS1624 The body of 'UserQuery.ProjectEuler4.FindLargestPalindromeProduct(int, int, IEnumerable<int>)' cannot be an iterator block because 'int' is not an iterator interface type

Jeroen Vannevel

yield return methods ("iterator blocks") must have a return type of IEnumerable<T>

because you are, literally, returning a collection of elements but rather than creating the entire collection and returning it after it's created, you hand back elements one-by-one

Maybe you just meant to use return without yield?

Phrancis

Maybe that's the case, let me try. I just want the loop to break as soon as it finds one value that matches the conditions

Quill

that would be return

Pimgd

@N3buchadnezzar writing answers?

Phrancis

10:57 PM

Getting a different error this time

> Cannot return a value from an iterator. Use the yield return statement to return a value, or yield break to end the iteration.

Pimgd

codereview.stackexchange.com/users/49350/pimgd?tab=answers

N3buchadnezzar

@Pimgd shackles fist angrily

Pimgd

15 answers, 29 upvotes, 4 accepts - that'll get you some rep

Jeroen Vannevel

remove all yield return statements

and just use return

Captain Obvious

0

Q: Modelisation of a chain of springs

I'm writing a program which modelises the behaviour of a chain of springs when subjected to user-inputted force impulsions. Note : I've not included the real code as it is long and cluttered, and I only want advice on a specific part of the implementation for now. So I have an object Chain,...

Pimgd

10:58 PM

aaaand bold text died, GG chrome

N3buchadnezzar

@Pimgd 395 this week

Phrancis

@JeroenVannevel Ohhhh, very nice, works like a charm now :)

Pimgd

@N3buchadnezzar codereview.stackexchange.com/users/49350/pimgd?tab=reputation

you can see a detailed log if you're interested

N3buchadnezzar

Aweosme!

Phrancis

So in this method, yield return works because the method returns an IEnumerable, right?

private static IEnumerable<int> GetAllPalindromes(int min, int max)
{
    for(var i = (max * max); i >= (min * min); i--)
    {
        if (IntUtils.IsPalindrome(i))
        {
            yield return i;
        }
    }
}

Jeroen Vannevel

11:02 PM

yes

arda

aaand I officially killed the biggest part of the project I'm working to improve

Thankfully, #sourcecontrol (fixed)

Vogel612

24 hours left on [tag:java][tag:javafx] bounty

arda

you can't use tags

Phrancis

@JeroenVannevel Is working with IEnumerable<T> usually faster than working with List<T>?

(I realize they are not quite the same thing, just asking in general)

Jeroen Vannevel

There's so different, you can't really compare it

it depends on the situation

Vogel612

11:04 PM

IEnumerables can be lazy which can be faster

Jeroen Vannevel

the thing you have to realize is that an IEnumerable sometimes represents something.. unmaterialized

Vogel612

Lists are eager, which can be faster for other cases

Jeroen Vannevel

Like a LINQ query. Depending on the query, it basically acts as a blueprint that doesn't do anything by itself

like collection.Where(x => x.Age > 5)

That won't do shit

it's a blueprint that tells you to get all people over the age of 5

collection.Where(x => x.Age > 5).ToArray(), however, will use that blueprint and create an array out of it

these are materializing queries

Vogel612

@JeroenVannevel actually... it will

Phrancis

Makes sense I suppose

Jeroen Vannevel

11:07 PM

There are several of them: ToList() and ToArray() but also Select(), FirstOrDefault() OrderBy() and Take() for example

they all perform some sort of materialization

@Vogel612 how so?

Mat's Mug

yield has many implications compiler-wise @Phrancis. What's running is so much more than what you write ;-)

Vogel612

it's a filter. just because it's not eager, that doesn't mean there is no result

54

A: LINQ extension methods - Any() vs. Where() vs. Exists()

Where returns a new sequence of items matching the predicate. Any returns a Boolean value; there's a version with a predicate (in which case it returns whether or not any items match) and a version without (in which case it returns whether the query-so-far contains any items). I'm not sure abou...

Phrancis

@Mat'sMug Sounds like I got some reading to do

Vogel612

> Where returns a new sequence of items matching the predicate.

Captain Obvious

0

Q: Organisation of javascript functions on a single web page

I've created a web page for display a list of products that I get from a JSON string through an AJAX call. On this page I have several javascript functions in the head of the html file. I'd like to know what the best way would be for organising my code. In the head of my html code I have pretty ...

javascript beginner

Mat's Mug

11:09 PM

@Phrancis C# in Depth by Jon Skeet covers it very nicely

@Vogel612 but it doesn't iterate the results

Vogel612

'course not.

that still doesn't mean it has no effect

Jeroen Vannevel

> This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

msdn.microsoft.com/en-us/library/bb549418(v=vs.100).aspx

Mat's Mug

^

Quill

Those are called promises in JS

Jeroen Vannevel

no they aint

Mat's Mug

11:10 PM

It has no immediate effect then ;-)

Phrancis

Wow, refactoring my code based on the answers I got made by biggest test case go from 27s to 0.184s

Jeroen Vannevel

promises are async stuff

Vogel612

@Quill nope those are different

Quill

kinda sorta maybe

Mat's Mug

@Quill that would be a Task<T> I think

Jeroen Vannevel

11:10 PM

sorta maybe nope

Mat's Mug

Totally another thing

Or just a Task. Whatever.

@JeroenVannevel not a task?

Phrancis

Po-ta-to, Po-tah-to ... ;)

Jeroen Vannevel

@Mat'sMug Yes, Task or Task<T>, both are fine

I was answering @Quill

Mat's Mug

@Phrancis promises, pro misses

Duga

If this works, but you want it to be better, why not use the Code Review Stack Exchange instead? — zero298 54 secs ago

Duga

11:29 PM

@SonuMishra: That's where eyes come in! I see why people use this, but I believe that it lulls people into a false sense of security, AND I believe that if you're not paying enough attention to spot a = vs ==, then what else are you missing? Pay more attention. Simply read your code. :) And get your colleagues to code review. tl;dr If you're missing this, you're almost certainly missing other things that yoda conditionals do not solve for you. — Lightness Races in Orbit 49 secs ago

Phrancis

> 0==i is called a "yoda conditional". It is most certainly a personal preference, but it does have an advantage.

It was used in the dark ages by mystical knights of the realm who lacked the modern technology to tell them when they'd written 0=i by mistake.

lmao

N3buchadnezzar

11:43 PM

# I love Latex again

folk.ntnu.no/oistes/Diverse/Project-Euler.pdf

Latex can even make the title of the colorboxes automatically link to the Project Euler problem on the internet.

Captain Obvious

0

Q: Neural net in C++

I wrote a Matrix struct and a neural net that uses it. Why is this slow? Gprof blames Matrix::operator()(int, int) which I suppose is my constructor, and Matrix::operator*(Matrix) and vector<float>::operator[]. #include <iostream> //#include <C:/Users/David/Google Drive/Coding/neural_c/Launcher.h>...

c++ performance neural-network

Phrancis

@N3buchadnezzar Just curious, do you have any license concerns putting together a document like this?

(I'm not sure what license terms the PE website/content has)

Ah, looks like you're OK projecteuler.net/copyright

As long as not used commercially

N3buchadnezzar

@Phrancis They have a policy of saying please do not. However the solutions are already just a google search away.

@Phrancis Yeah.

Phrancis

Just need to make sure your document is also CC BY-NC-SA 2.0 UK

N3buchadnezzar

Darn it I was thinking of selling it on the streets to addicted programers =(

Phrancis

11:56 PM

LOL

N3buchadnezzar

However my idea with the document is not solutions. But overly optimized and generalized solutions . Not quite sure how to make that as clear as possible

Phrancis

Just write an Introduction/About page that precedes the index/table of contents

Short, to the point. Or even a subtitle would work

Transcript for