C# Constructors with similar arguments

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I am working on a script that takes 3-4 inputs and creates a line formula from this. The formula is then used in line calculations, like collisions. The problem is the line formula has 4 versions that allows you to use 3 floats to construct it. These constructors are conflicting with each other.

I found some old code of mine where I did the same thing but with single integer inputs. So I copied my code and it is working but I don't know if what I am doing is correct.Debugging proved it works, Code:

Spoiler


//This is the class that is used for a line formula
public class LineFormula {
// The formula is Y = Slope*X + B where B is the Y Intersect
public float Y,Slope,X,B;

//A empty one can also be made
private LineFormula()
{
//Empty class only for constructing inside  constructor
}

//When we make the formula we can store all the data
public LineFormula(float InX,float InY,float InSlope, float InB)
{
Y = InY;
Slope = InSlope;
X = InX;
B = InB;
}
//Find Y on construct
//Y = Slope*X + B // 66 = (30*2) + 6
public static LineFormula FindY(float InX,float InSlope, float InB)
{
var LineFormula = new LineFormula();
LineFormula.Y = (InSlope*InX) + InB;
LineFormula.Slope = InSlope;
LineFormula.X = InX;
LineFormula.B = InB;

return LineFormula;
}
//Find X on construct
// X = (Y-B) / Slope; // 2 = (66-6) /30
public static LineFormula FindX(float InY,float InSlope, float InB)
{
var LineFormula = new LineFormula();
LineFormula.Y = InY;
LineFormula.Slope = InSlope;
LineFormula.X = (InY - InB) / InSlope;
LineFormula.B = InB;

return LineFormula;
}
//Find slope on construct
//Slope = (Y-B)/X 	//30 = (66 -6) /2   // 1 = (1-0)/1
public static LineFormula FindSlope(float InX,float InY, float InB)
{
var LineFormula = new LineFormula();
LineFormula.Y = InY ;
LineFormula.Slope = (InY - InB) / InX;
LineFormula.X = InX;
LineFormula.B = InB;

return LineFormula;
}

//Find Y intersect(B) on construct, doesn't look like I need this one.
//B = Y - (Slope*X) //6 = 66 - (30*2)
public static LineFormula FindB(float InX,float InY, float InSlope)
{
var LineFormula = new LineFormula();
LineFormula.Y = InY ;
LineFormula.Slope = InSlope;
LineFormula.X = InX;
LineFormula.B = InY - (InSlope * InX);

return LineFormula;
}
}

I don't understand my own code here:

var LineFormula = new LineFormula(); This tells me I made a new empty version of the class, inside of the class so there is 2 now? If there is two then what happens to one after return, is it waiting for garbage collection now? Why the static?

Is this even a valid way to create similar arguments? Is there better ways? I checked online and found programmers using interfaces to make similar arguments.

I think it made sense to me back then, but I have forgotten it as I never needed to use it again.

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1 hour ago, Scouting Ninja said:

This tells me I made a new empty version of the class, inside of the class so there is 2 now?

No - you only call 'new LineFormula' inside static functions, which are basically much the same as global functions in that they don't require an instance of the class, except they exist within the class's scope. i.e. LineFormula.FindY doesn't require an instance of LineFormula to run, but it does return a new instance when it completes.

This is pretty much just 3 'factory' functions, which is a common pattern for constructing objects that have complex parameters and therefore constructors alone may not suffice.

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1 hour ago, Kylotan said:

No - you only call 'new LineFormula' inside static functions... LineFormula.FindY doesn't require an instance of LineFormula to run

Thanks, this alone clears up a lot of my concerns with using this. So now I know I am not making a extra copy and the static makes it similar to a global function.

1 hour ago, Kylotan said:

This is pretty much just 3 'factory' functions

What is meant by "Factory" functions? I see this term a lot while researching how to make similar arguments. Please in layman terms.

Sorry if my questions seam obvious, I learned coding in a weird way where I know advance stuff but am missing some of the basics.

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Posted (edited)

factory functions make things. Think: factory. Like China Factory.

Edited by h8CplusplusGuru

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Posted (edited)
8 hours ago, Scouting Ninja said:

The problem is the line formula has 4 versions that allows you to use 3 floats to construct it. These constructors are conflicting with each other.

Assuming I understand this correctly, you would't want it as different constructors anyway. When constructing such an object, it would be highly ambiguous anyway! I suppose your old code fixes this with having these as the functions you've presented here, which is a much better approach: calling FindX shows me that what it is calculating is X from the given parameters.

As for yoru code, most has been explained already: you've got several factory functions (i.e. those functions create an instance based on the provided arguments and do require an instance of the class to call them on). That being said the comments at the start of the first constructor are very confusing

8 hours ago, Scouting Ninja said:

//A empty one can also be made private LineFormula() { //Empty class only for constructing inside constructor

An empty one can be made, but obviously only from inside the class as it's private. The second comment should probably read 'Empty constructor for constructing inside class', although I'd find 'Zero parameter constructor' or something alike a better wording. I'm not sure if you've added these for this post or if these were in code already, but either way, it's really quite redundant.

6 hours ago, Scouting Ninja said:

static makes it similar to a global function.

In c# there's no actual notion of global functions, making static more or less the replacement. They're still functions of a class, but they do not run on an instance; in fact iirc they're not allowed to either. So you can't do

class Foo
{
static void Bar();
}

...

Foo x;
x.Bar();

And have to call Foo::Bar explicitly.

Code looks correct other than that, but it's more of a calculation result than a LineFormula. In all honesty, having the class be returned is already quite redundant: these functions only require you to return a single float, all the other information is what you passed into the function already

Edited by AthosVG

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8 minutes ago, AthosVG said:

Assuming I understand this correctly, you would't want it as different constructors anyway.

The thing is I do want it as a constructor for use. These line formulas create theoretical infinity lines, that is what the formula is for.

So once a line is made I want to store it for use but to never change it again, every line instance will then be a line in the world and can only be read from or destroyed. Since this posts the variables are private with get functions.

12 minutes ago, AthosVG said:

calling FindX shows me that what it is calculating is X from the given para﻿meters.

I agree now that I have been using it this looks cleaner, I know what part is calculated where if it was only constructs it would have been impossible to know what I was calculating.

13 minutes ago, AthosVG said:

I'm not sure if you've added these for this post or if these were in code already

I am not a programmer, so I need to keep notes of what every little thing does or I could delete or change a important part of a script. All of my code has these redundant text that describes each and every step.

I could work on a piece of code today, get it working, then next week I have no idea what it does or how.

18 minutes ago, AthosVG said:

In c# there's no actual notion of global functions, making static more or less the replacement.

Thanks for explaining this to me, makes things a little clearer.

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Tenth place
Source: Anomalies in X-Ray Engine
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BOOL CActor::net_Spawn(CSE_Abstract* DC) { .... m_States.empty(); .... } PVS-Studio warning: V530 The return value of function 'empty' is required to be utilized.
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Ninth place
Source: Long-Awaited Check of CryEngine V
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void CCryDXGLDeviceContext:: OMGetBlendState(...., FLOAT BlendFactor[4], ....) { CCryDXGLBlendState::ToInterface(ppBlendState, m_spBlendState); if ((*ppBlendState) != NULL) (*ppBlendState)->AddRef(); BlendFactor[0] = m_auBlendFactor[0]; BlendFactor[1] = m_auBlendFactor[1]; BlendFactor[2] = m_auBlendFactor[2]; BlendFactor[2] = m_auBlendFactor[3]; *pSampleMask = m_uSampleMask; } PVS-Studio warning: V519 The 'BlendFactor[2]' variable is assigned values twice successively. Perhaps this is a mistake.
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Source:  Unicorn in Space: Analyzing the Source Code of 'Space Engineers'
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Seventh place
Source: Analyzing the Quake III Arena GPL project
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void Terrain_AddMovePoint(....) { .... x = ( v[ 0 ] - p->origin[ 0 ] ) / p->scale_x; y = ( v[ 1 ] - p->origin[ 1 ] ) / p->scale_x; .... } PVS-Studio warning: V537 Consider reviewing the correctness of 'scale_x' item's usage.
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Sixth place
Source: Checking the Unity C# Source Code
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public override bool IsValid() { .... return base.IsValid() && (pageSize >= 1 || pageSize <= 1000) && totalFilters <= 10; } PVS-Studio warning: V3063 A part of conditional expression is always true if it is evaluated: pageSize <= 1000.
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Fifth place
Source: Discussing Errors in Unity3D's Open-Source Components
This place was given to a nice bug found in Unity3D's components. The article mentioned above was written a year prior to revealing Unity's source code, but there already were interesting defects to find there at the time.
public static CrawledMemorySnapshot Unpack(....) { .... var result = new CrawledMemorySnapshot { .... staticFields = packedSnapshot.typeDescriptions .Where(t => t.staticFieldBytes != null & t.staticFieldBytes.Length > 0) .Select(t => UnpackStaticFields(t)) .ToArray() .... }; .... } PVS-Studio warning: V3080 Possible null dereference. Consider inspecting 't.staticFieldBytes'.
Note the lambda expression passed as an argument to the Where method. The code suggests that the typeDescriptions collection could contain elements whose staticFieldBytes member could be null – hence the check staticFieldBytes != null before accessing the Length property. However, the programmer mixed up the '&' and '&&' operators. It means that no matter the result of the left expression (true/false), the right one will also be evaluated, causing a NullReferenceException to be thrown when accessing the Length property if staticFieldBytes == null. Using the '&&' operator could help avoid this because the right expression won't be evaluated if staticFieldBytes == null.
Although Unity was the only engine to hit this top list twice, it doesn't prevent enthusiasts from building wonderful games on it. Including one(s) about fighting bugs.
Fourth place
Source:  Analysis of Godot Engine's Source Code
Sometimes we come across interesting cases that have to do with missing keywords. For example, an exception object is created but never used because the programmer forgot to add the throw keyword. Such errors are found both in C# projects and C++ projects. There was one missing keyword in Godot Engine as well.
Variant Variant::get(const Variant& p_index, bool *r_valid) const { .... if (ie.type == InputEvent::ACTION) { if (str =="action") { valid=true; return ie.action.action; } else if (str == "pressed") { valid=true; ie.action.pressed; } } .... } PVS-Studio warning: V607 Ownerless expression 'ie.action.pressed'.
In the given code fragment it is obvious that a programmer wanted to return a certain value of the Variant type, depending on the values ie.type and str. Yet only one of the return statements – return ie.action.action; – is written properly, while the other is lacking the return operator, which prevents the needed value from returning and forces the method to keep executing.
Third place
Source: PVS-Studio: analyzing Doom 3 code
Now we've reached the Top-3 section. The third place is awarded to a small code fragment of Doom 3's source code. As I already said, the fact that a bug may look straightforward to an outside observer and make you wonder how one could have made such a mistake at all shouldn't be confusing: there are actually all sorts of bugs to be found in the field...
void Sys_GetCurrentMemoryStatus( sysMemoryStats_t &stats ) { .... memset( &statex, sizeof( statex ), 0 ); .... } PVS-Studio warning: V575 The 'memset' function processes '0' elements. Inspect the third argument.
To figure this error out, we should recall the signature of the memset function:
void* memset(void* dest, int ch, size_t count); If you compare it with the call above, you'll notice that the last two arguments are swapped; as a result, some memory block that was meant to be cleared will stay unchanged.
Second place
The second place is taken by a bug found in the code of the Xenko game engine written in C#.
Source: Catching Errors in the Xenko Game Engine
private static ImageDescription CreateDescription(TextureDimension dimension, int width, int height, int depth, ....) { .... } public static Image New3D(int width, int height, int depth, ....) { return new Image(CreateDescription(TextureDimension.Texture3D, width, width, depth, mipMapCount, format, 1), dataPointer, 0, null, false); } PVS-Studio warning: V3065 Parameter 'height' is not utilized inside method's body.
The programmer made a mistake when passing the arguments to the CreateDescription method. If you look at its signature, you'll see that the second, third, and fourth parameters are named width, height, and depth, respectively. But the call passes the arguments width, width, and depth. Looks strange, doesn't it? The analyzer, too, found it strange enough to point it out.
First place
Source: A Long-Awaited Check of Unreal Engine 4
This Top-10 list is led by a bug from Unreal Engine. Just like it was with the leader of "Top 10 Bugs in the C++ Projects of 2017", I knew this bug should be given the first place the very moment I saw it.
bool VertInfluencedByActiveBone( FParticleEmitterInstance* Owner, USkeletalMeshComponent* InSkelMeshComponent, int32 InVertexIndex, int32* OutBoneIndex = NULL); void UParticleModuleLocationSkelVertSurface::Spawn(....) { .... int32 BoneIndex1, BoneIndex2, BoneIndex3; BoneIndex1 = BoneIndex2 = BoneIndex3 = INDEX_NONE; if(!VertInfluencedByActiveBone( Owner, SourceComponent, VertIndex[0], &BoneIndex1) && !VertInfluencedByActiveBone( Owner, SourceComponent, VertIndex[1], &BoneIndex2) && !VertInfluencedByActiveBone( Owner, SourceComponent, VertIndex[2]) &BoneIndex3) { .... } PVS-Studio warning: V564 The '&' operator is applied to bool type value. You've probably forgotten to include parentheses or intended to use the '&&' operator.
I wouldn't be surprised if you read the warning, looked at the code, and wondered, "Well, where's the '&' used instead of '&&'?" But if we simplify the conditional expression of the if statement, keeping in mind that the last parameter of the VertInfluencedByActiveBone function has a default value, this will clear it all up:
if (!foo(....) && !foo(....) && !foo(....) & arg) Take a close look at the last subexpression:
!VertInfluencedByActiveBone(Owner, SourceComponent, VertIndex[2]) &BoneIndex3 This parameter with the default value has messed things up: but for this value, the code would have never compiled at all. But since it's there, the code compiles successfully and the bug blends in as successfully. It's this suspicious fragment that the analyzer spotted – the infix operation '&' with the left operand of type bool and the right operand of type int32.

Conclusion
I hope I have convinced you that static analysis is a very useful tool when developing video games and game engines, and one more option to help you improve the quality of your code (and thus of the final product). If you are a video game industry developer, you ought to tell your coworkers about static analysis and refer them to this article. Wondering where to start? Start with PVS-Studio.