Fake Programmers

Tom Wijsman

00:03

@fr33: This is chromium, I haven't touched it.

Stack trace is at bpaste.net/show/55306 and have reported it, appears a bug where WebCore talking with v8 is going wrong.

fr33

02:21

Thanks for the notice

KronoS

03:16

and thus beings my all nighter...

@TomWijsman you around? I know it's super late for you...

fr33

03:44

Hello knonos

I was expecting you

fr33

04:18

"Sorry for not being too cool to be spoken to :L"

KronoS

05:05

@fr33 I was having issues

fr33

Ok, my bad ;L

I hope your issues were resolved

KronoS

@Bob do you know anything about overloading the == operator in c++?

They were

Bob

@KronoS something, yes. much? no :P

fr33

cool

KronoS

// Overloads==
bool operator== (const Vertex &n1, const string &n2)
{
	return n1.getName() == n2;
}

is it possible to do something like this?

actually we should migrate over to fake programmers

fr33

05:07

so did you got fixed the problem you had with the list not being a template type or something like that yesterday?

KronoS

@fr33 yes... @TomWijsman was very helpful

// Overloads==
bool operator== (const Vertex &n1, const string &n2)
{
	return n1.getName() == n2;
}

so is this possible?

fr33

let me see....

Bob

overloading == is definitely possible

but there's only one parameter/argument

fr33

yes it is, but in that particular case

Bob

you use this to refer to the LHS

KronoS

05:09

I've got a list of Vertex's but want to compare it's name (a string) to a known string value

Bob

You would do something more like

// Overloads==
bool operator== (const string &other)
{
	return this->getName() == other;
}

KronoS

@Bob that doesn't work

Bob

o.O

fr33

use a pointer instead of unary resolution operator?

KronoS

Error:operator has too few arguments

Sathya

05:11

← 5 messages moved from Root Access

fr33

why wont the object call wont work as suppose using the unary resolution operator (.)?

seems that it should

had you tested?

Bob

ok, now I'm confused... the few times I've done that, I've used a single argument. some sources say that. some other sources say use two arguments

fr33

well you just comparing the operator variable with two different others at the time... although I think would be better if you separate the condition in two

KronoS

@Sathya thank you

Bob

@fr33 not so much the comparing, more the function prototype. Is it bool operator==(const Type &LHS, const Type &RHS) or bool operator==(const Type &other)?

fr33

05:14

ok, my bad I thought it was comparison, but is not is initialization

Sathya

@KronoS welcome.

Bob

ah, I see

fr33

but still you want to know if LHS type and RHS match or so to make the call using the object

Bob

@KronoS is this a member function?

fr33

right?

get name should be a member function...

Bob

05:17

i.e. is it declared/defined within the class?

if so, use the since argument. if not, use two arguments

fr33

u meant single argument?

ok, at least say yes, no, may be, I think is quite rude, to just leave other people expectation of an answer just hanging in the air ;L

KronoS

screw it... I just migrated to this:

// Add a child node to the parent.
void Graph::AddChildNode(Vertex * const aChildVertex, const string aParent)
{
	for(list<Vertex>::iterator it = mInternalGraph.begin(); it != mInternalGraph.end(); it++)
	{
		if(it -> getName().compare(aParent) == 0)
		{
			it -> addEdge(aChildVertex));
			break;
		}
	}
}

Bob

well

your original one should have worked :P

KronoS

@Bob but was too much for me to try to figure out ATM

Bob

provided you used -> and dereferenced the string, of course

wait

is it getting passed pointers or.. argh

I remember why I abandoned C++ now

fr33

05:23

ha ha, pointers screw things if use wrongly

Bob

ok, forget anything I said in the last hour :P

5

Q: What's the ampersand for when used after class name like ostream& operator <<(...)?

I know about all about pointers and the ampersand means "address of" but what's it mean in this situation? Also, when overloading operators, why is it common declare the parameters with const?

KronoS

lol

I hate c++ right now. I'm sure it's got its advantages, but right now... I don't like it one bit

fr33

reference

Bob

oh. pass by reference.

facepalm

how did I forget that

fr33

I remember that & was for reference

lol

Bob

05:26

must be too much C# ref, VB ByRef, Python WhatTheHeckIsGoingOn

fr33

ha ha, doing C#, cool same here ;)

Bob

so, basically, your first code snippet looks alright @KronoS :S

fr33

just passing the place the actual space of the variable is, not actually passing a copy (as per argument does) so if the value of variable is modified, the actual variable changes, as opposed with pass-by-arguments (copy)

Hey bob had you work with XNA/C# specially with SB?

Bob

@fr33 yea, I know what passing by ref does :P just the meaning of & slipped my mind

fr33

Yeah I know you know what it was, just want it to mention it, tho...

Bob

05:31

@fr33 I've only done WinForms and Console with C#. Tried XNA once, but never had the time to really learn. No idea what SB is.

fr33

:L ok, cool, SB is SunBurn, just an game engine made with XNA/C#

thanks tho :)

KronoS

@Bob glad I wasn't the only one

fr33

isn't the whole point of C# being C# is outwit C++?

lI know it similar to Java, but it is C++ on steroids... Or that's too much...?

BUMP!

KronoS

@fr33 I wouldn't go that far... C# is lacking in a lot of areas that C++ excels in

fr33

Yeah, but those areas might sometimes be advantageous at some aspects and sometimes not

like for example pointers, yes good, but in the hands of an inexperienced programer is too dangerous

you can always do wrappers if you need exactly a special functionality of a language in your program

KronoS

06:38

hey @Bob how do I copy directly contents of a list in c++?

for example say I have a list<vertex> foundVertices that I want to pass into a constructor of a class Graph

Grrr... I'm having a problem with my pointers...

fr33

06:51

What are you trying to acomplish as a whole?

like are you building an engine, a game, a visual library? What?

KronoS

I'm building a graph

lol

that's about it right now

fr33

ohh ok, and for a graph you passing such bunches of trouble... ;D

KronoS

www2.engr.arizona.edu/~ece474a/Main/Assignment2

that's what I'm doing specifically

fr33

look unnecessarily tedious

looks*

lol

Bob

@KronoS what, create a copy of the entire list?

KronoS

06:58

@Bob I've got a list of pointers that no longer point to anything after returning the list

it's actually like this:

list of vertices

each vertex has a list of pointers to other vertices in the top list

this second list isn't working properly

fr33

so basically is a list of list?

Bob

o.O

self...referential...lists?

fr33

list of vetex which each one contains a list of pointers?

KronoS

let's say I have a graph like this

fr33

isn't that a graph data structure?

KronoS

07:00

1 -> 2 && 1->3

The graph would have 3 nodes (top list)

fr33

yes it is

KronoS

the first node, would reference the other two (edges or second list)

Bob

ahhh

KronoS

The second list is a list of pointers. These pointers point to actual nodes in the graph

fr33

inst a graph works with trees and leaves

Bob

07:01

and you're using linkedlists.

KronoS

@Bob yes...

(I think lol)

Bob

normally, I'd just to this with an array (if int indexes) or a map (if unique key indexed)... but if yo uwanna do it this way.. :P

KronoS

class Vertex
{
private:
	string mName, mColor;
	list<Vertex *> mEdges;
	Vertex * mPredecessor;
	float mDelay, mDist;
	int mFinish;

public:

	// Constructor
	Vertex();

	// Getters:
	const string getName() const;
	const list<Vertex *> getEdges() const;
	const Vertex * getPredecessor() const;
	const float getDelay() const;
	const float getDistance() const;
	const int getFinish() const;
	const string getColor() const;

	// Setters:
	const void setName(string aName);
	const void addEdge(Vertex * aEdge);

That's my Vertex class

fr33

using linked list it ain't bad, but a linked list of linked list is too much spaghetti code?

Bob

why are you using a llist anyway?

any specific advantage?

KronoS

07:04

@Bob I don't know the size of the graph before hand

but I guess I could use arrays

just set them to a max size of something ridiculous (since all I'll ever hit is like 20 nodes tops)

I just don't know how TBH...

Bob

hm.. llists are great for insertion/removal, but if you're only adding to the end of the array/list (relatively rarely) then there isn't too much penalty in using a vector

KronoS

@Bob vector?

Bob

vector.

dynamically sized array, essentially

part of the STL

fr33

1 colum, many rows data structure

Bob

vector<int> myVector;
myVector.push_back(5);

but then you can access it like an array

myVector[0] == 5;

bleh, nothing wrong with llists

KronoS

07:08

@Bob push_back(someValue) sets the value to the back of the list?

Bob

@KronoS the end, yes

KronoS

I don't think though this is going to solve my problem... somehow my pointers are getting lost

Bob

it's a dynamically sized array

yea, there is that :P

wait a sec

KronoS

list, vector, array... shouldn't matter

Bob

anyways, you wanted each node to have a list containing a pointer to every other node?

KronoS

07:11

@Bob right

@Bob here's my prob... I have a GraphReader class that creates the graph

Bob

I'm just running a few things through ideone as a basic proof of concept :P

I assume you don't want the node to refer to itself?

KronoS

The graph within this graphReader is fine, BUT if I try to return that graph... the pointers get lost

@Bob no

I take that back

the graphreader class graph isn't good

I'm thinking that it's a scope issue

So here's what I do (I'm turning to the rubber ducky method so feel free to ignore):

1. I have a constructor for the GraphReader

This constructor read the file for the graph and converts that file into a graph

the graph that is parsed there is good (has the correct pointers and such)

As soon as the constructor is done, those pointers are lost

Bob

hm

could you paste that constructor?

most likely using a stack variable :\

KronoS

It's nasty... I'm warning ya...

pastebin.com/9gny4hx5

Bob

egads that's long

KronoS

07:24

I told you

@Bob look at line 306

Bob

and you're losing all the pointers when it leaves the constructor?

KronoS

@Bob ya

Bob

erm

brb testing something

KronoS

hey @IvoFlipse

Ivo Flipse

Morning :)

KronoS

07:34

@IvoFlipse It's almost morning here :P

about 26 mins away ;)

and I'm still stuck on pointer issues

Ivo Flipse

Here I thought my AI-class stuff was annoying :P

KronoS

I'm frustrated becuase I don't feel like I'm actually learning the skills I should be learning, but rather having to deal with debugging stupid issues that take up way too much of my time

Ivo Flipse

I need to calculate the sum over all possible transitions between s and s' and stuff, blegh

@KronoS That sounds like a useful skill to me :)

sadly I still don't know enough C++ to be of much use to troubleshoot a pointer issue

Bob

yay, massive overflow of STL errors :P

KronoS

@Bob lol

Bob

07:43

ok, so make of this what you will: ideone.com/AzsXmW

fr33

for me is still night

I know is 3:44 AM but, haven't got to sleep so...

@Ivo

when I see it I let you know if is annoying ;p

Ivo Flipse

@Bob Not a bad idea, @KronoS rip out the offending loop and try to simulate how it works in a barebone file

Though perhaps you don't have to, just strip make sure it stops doing anything when it hits that function, so you can see what the heck is going on

Bob

@IvoFlipse that was just to check/prove whether or not the pointers were lost when exiting the constructor

:S

appears not

oh, wait, I forgot

KronoS

@Bob ya those aren't pointers...

or am I reading this wrong?

Bob

no problems here: ideone.com/8DtshX

I'm gonna reread your code :P

KronoS

07:51

Maybe it's when I return the Graph it's return a copy

and therefore those pointers do point to nothing...

but then, why wouldn't the GraphReader's graph be incorrect :/

Bob

you're saving it in mParsedGraph?

KronoS

@Bob ok I see what you're doing.. and ya that does prove it works... Except the extra step that I'm doing is pasing that list out to another class

@Bob yes

So it's like this:

1. Main Execution Class:

- calls the GraphReader, who creates a Graph

- Saves the GraphReaders Graph into a new Var

After execution of the Constructor, the graphs pointers aren't correctly pointing...

Ivo Flipse

@KronoS Doesn't this return a pointer/reference you can just keep track off?

KronoS

@IvoFlipse Ya I was thinking about that... but even then the pointer wouldn't matter, becuase the pointers within the object are the issue

Ivo Flipse

Could you put your code into a pastebin again?

Bob

07:56

@KronoS Is that done by GraphReader?

Ivo Flipse

@KronoS So test them before you pass it and after you pass it

KronoS

GraphReader takes a file input, and read the file, and then creates a basic graph, and stores it internally

Before exiting the Constructor, everything looks fine:

	mParsedGraph = Graph(mParsedVertices);
}

line 106 of GraphReader.cpp is executed and the graph processes correctly

Ivo Flipse

Don't you have to return that graph or is the processing function just part of graphreader?

why don't you pass graph a pointer and say: make that darn graph over here

KronoS

Now that's an interesting Idea....

Bob

@IvoFlipse it's a constructor

a constructor is called when a class is created

iirc, it returns, well, itself as an object

Ivo Flipse

08:00

yeah, but what happens to mParsedGraph? He creates it, then its immediately destroyed, because its not bound to GraphReader is it?

in Python you'd have to say: self.mParsedGraph = blabla

without the self reference, it would execute then happily let it go out of scope

Bob

I assumed mParsedGraph was a member variable...

that is, a heap variable that lives as part of the object/class

C++ doesn't require this (equivalent of self). When I first used Python, self through me off...

though it could very well be the problem

that it's not assigning to the correct variable :P

Ivo Flipse

Hence, just pass Graph something along you want to store it in/at

Bob

that kinda defeats the point of a constructor, which is to initialise member variables (among other things)

in any case, nothing wrong with copying: ideone.com/s69tXP

so, yea, go listen to @IvoFlipse :P

I'm probably wrong about everything, as usual

KronoS

OH HEY!

It worked!

by golly @IvoFlipse you're a genius!

well kinda lol :P

@Bob you were quite helpful as well

Ivo Flipse

Now you get another error :P

KronoS

08:10

Yes.... but I still have another half bottle of diet Dr. Pepper... :P

Ivo Flipse

In Python I would have spotted this, because the default return value is None. So if you expect a value and get None, well you didn't return anything :P

KronoS

@IvoFlipse I actually don't know what was wrong here and I'd be interested to see why this worked and the constructor didn't (but on another day)

Ivo Flipse

I'd be interested to know why my calculations were off too, but guess we'll never know :P

KronoS

Fact is, my specific case, the constructor somehow loses the pointers within the graph, BUT NOT the actual objects themselves. They passed through just fine

Ivo Flipse

Doesn't it just pass a null pointer or something in that case?

KronoS

08:13

@IvoFlipse no... the other thing that makes this more sucky is that I have to use CMake

so things get even weirder

Ivo Flipse

Don't get me started, that part really put me off C++

KronoS

like I said... let me work with Python when it needs to be multi platform

Ivo Flipse

Lets see to Qk+1(s,a) = Sum of all prime (T(s,a,s') * [R(s,a,s') + gamma * max Qk (s',a')]

So if I'm in s=A and the action a=Clockwise, then I have two possible s': B and C

T = 0.8 * [R = 0.0 + gamma = 0.5 * Q(s',a') = 0.8] = 0.32

Unless, Q(s',a') is another value, because s' in this case is B or C, so if I assume B, because that's where I'm heading, it could be 0.0 or 4.32. You take the max, so its 4.32

0.8 * [ 0.0 + 0.5 * 4.32] = 1.728 for B

0.2 * [-4.0 + 0.5 * 1.76] = -0.624

Add them up = 1.104

Voila, I found my mistake :)

You guys are such great rubber duckies

KronoS

@IvoFlipse we do what we can :P

Bob

08:30

I should change my gravatar :P

Now where's a good rubber duck picture...

KronoS

Bob

@KronoS Is it correct at the very end? After that last assignment?

KronoS

@Bob what do you mean?

Bob

@KronoS Have you checked for correctness after mParsedGraph = Graph(mParsedVertices);?

KronoS

@Bob ya... it actually looks like this:

return Graph(mParsedVertices);

// Constructor
Graph::Graph(list<Vertex> aRawGraph)
{
	mInternalGraph = aRawGraph;
}

Ivo Flipse

08:36

argh, I hate exercises where one mistake means all numbers are reset :(

Bob

@KronoS wait.. why return in a constructor?

That makes no sense whatsoever

KronoS

@Bob IM NOT TOUCHING IT :p

Bob

4

Q: return type of the constructor in C++

I know that there is no return type of the constructors in C++ However, the code below compiles right. What is returned by the constructor in the code below? class A{ public: A() {} } A a = A(); //what is returned by A() here, why? Is there any conflict here?

c++ constructor

KronoS

It's returning a new object, if I understand correctly

Bob

A constructor does not have a return type, much like a void function

bleh, whatever works :P

KronoS

08:39

I don't know...

now you got me all scared...

Bob

...

I DON'T KNOW WHAT'S GOING ON WITH YOUR CODE

LET'S JUST SAY IT WORKS

Ivo Flipse

Take it out of the constructor, put it in a function, create the object, call the function

Bob

</shout off>

@IvoFlipse perfect :P

How about do it C style and forego objects entirely? :D

seriously, though, objects and classes in C++ give me a headache

Ivo Flipse

You should try Scala :P

Bob

part of the problem is I keep forgetting ot end class prototypes with a semicolon...

the one place (I think) where a semicolon should go after a }

KronoS

08:41

@Bob ya that's annoying

Bob

oh wait, that applies to enums too

KronoS

Grrrr.... where's @TomWijsman when you need him

Error	3631	error LNK2019: unresolved external symbol "private: class std::list<class Vertex,class std::allocator<class Vertex> > const __thiscall Graph::TopoSort(void)" (?TopoSort@Graph@@AAE?BV?$list@VVertex@@V?$allocator@VVertex@@@std@@@std@@XZ) referenced in function "public: float const __thiscall Graph::DAG_CriticalPath(void)" (?DAG_CriticalPath@Graph@@QAE?BMXZ)	D:\Repositories\ECE474\Project 3\synthesizer\build\src\Graph.obj	critpath

I hate these errors

Ivo Flipse

Link error, can't it find some library?

there's something DAG_criticalpath that it can't find

KronoS

Oh! Man it's getting late... I haven't implemented that method #facepalm

Bob

haven't?

Ivo Flipse

08:51

That's how late it is ;)

Bob

lol

the problem with Python: github.com/Elusive138/Windows-8-Challenge-Stats/blob/master/…

which reminds me, gotta fix it to return positive and negative infinity properly

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