Is there a way I can use groupBy(ConstraintCollectors.sum(x)) such as x is a variable of type Double ?
I don't want to round it to n decimal pointes then multiply by 10^n. I would like to use the Double variable as is.
As explained in an earlier answer, OptaPlanner does not provide means of working with double.
That said, ConstraintCollectors.sum() is simple and if you look up its implementation, you should be able to implement a double-based one easily. Use with caution.
Related
What is the reasoning for parsing an integer? For instance, Integer.Parse('variable'.text)
I see this a lot and while manipulating data for a calculator I am building I found that Val('variable'.text) was all I need to use "numeric" values.
So, my question is how does Integer.Parse() help me with regards to calculators?
Thanks!
I found that "Val('variable'.text)" was all I need
If that's the case then go ahead and use Val(). But be aware that it behaves differently than .Parse() (or, often preferably, .TryParse()) methods.
For example, what do you want to do if the user inputs "123 isn't 456"? Val() will (I think) return:
123 As Double
Or how about the input "123 456"? That would be:
123456 As Double
Do you want it to be a Double? Do you want it to throw an error because it's not purely numeric? Something else? The behavior you want should be reflected in the code you write. Use Val() for one set of behaviors, .Parse() for another.
Apologies if there's an answer out there already; but all I seem to be getting is a bunch of "I want to turn my 1 into a 1.0" chaff from my Google searches.
First things first. No, I'm not talking about a simple Convert::ToSingle() call. Rather, I need to convert the representation of the data to a System::Single.
So in other words, I'd like to take int myInt = 1065353216;, and the result should be something like 1.000. I know the pure c++ method would be something like float myFloat=*(float *)&myInt;;but I need the managed version.
Thanks in advance for your help.
If you're in C++/CLI, you can do it the same way as you do in C++: float myFloat=*(float*)&myInt;
In pure managed-land, there are built-in methods to do this for double & Int64 (DoubleToInt64Bits and Int64BitsToDouble, but not for single & Int32. However, if you look at the implementation of those methods (MS Reference Source), you'll see that they're doing the exact same thing as you have listed, so that's also the managed way to do it. The only difference is if you do it in C#, you have to tag the method as unsafe.
Converting a floating-point number to an integer using either CInt or CType will cause the value of that number to be rounded. The Int function and Math.Floor may be used to convert a floating-point number to a whole number, rounding toward negative infinity, but both functions return floating-point values which cannot be implicitly used as Integer values without a cast.
Is there a concise and idiomatic alternative to IntVar = CInt(Int(FloatingPointVar));? Pascal included Round and Trunc functions which returned Integer; is there some equivalent in either the VB.NET language or in the .NET framework?
A similar question, CInt does not round Double value consistently - how can I remove the fractional part? was asked in 2011, but it simply asked if there was a way to convert a floating-point number to an integer; the answers suggested a two-step process, but it didn't go into any depth about what does or does not exist in the framework. I would find it hard to believe that the Framework wouldn't have something analogous to the Pascal Trunc function, given that such a thing will frequently be needed when performing graphical operations using floating-point operands [such operations need to be rendered as discrete pixels, and should be rounded in such a way that round(x)-1 = round(x-1) for all x that fit within the range of +/- (2^31-1); even if such operations are rounded, they should use Floor(x+0.5), rather than round-to-nearest-even, so as to ensure the above property]
Incidentally, in C# a typecast from Double to Int using (type)expr notation uses round-to-zero semantics; the fact that this differs from the VB.NET behavior suggests that one or both languages is using its own conversion routines rather an explicit conversion operator included in the Framework. It would seem likely that the Framework should define a conversion operator? Does such an operator exist within the framework? What does it do? Is there a way to invoke it from C# and/or VB.NET?
After some searching, it seems that VB has no clean way of accomplishing that, short of writing an extension method.
The C# (int) cast translates directly into conv.i4 in IL. VB has no such operators, and no framework function seems to provide an alternative.
Usenet had an interesting discussion about this back in 2005 – of course a lot has changed since then but I think this still holds.
You can use the Math.Truncate method.
Calculates the integral part of a specified double-precision floating-point number.
For example:
Dim a As double = 1.6666666
Dim b As Integer = Math.Truncate(a) ' b = 1
I know this is an old case but I saw no one suggest the Math.Round() function.
Yes Math.Round takes a double and returns a double. However it returns a number that has been rounded to a whole number. It should easily and concisely convert to an integer using cInt. Would that suffice?
cInt(math.round(10000.54564)) ' = 10001
cInt(math.round(10000.49564)) ' = 10000
You may need extract the Int part of a float number:
float num = 12.234;
string toint = "" + num;
string auxil = toint.Split('.');
int newnum = Int.Parse(auxil[0]);
In algebra if I make the statement x + y = 3, the variables I used will hold the values either 2 and 1 or 1 and 2. I know that assignment in programming is not the same thing, but I got to wondering. If I wanted to represent the value of, say, a quantumly weird particle, I would want my variable to have two values at the same time and to have it resolve into one or the other later. Or maybe I'm just dreaming?
Is it possible to say something like i = 3 or 2;?
This is one of the features planned for Perl 6 (junctions), with syntax that should look like my $a = 1|2|3;
If ever implemented, it would work intuitively, like $a==1 being true at the same time as $a==2. Also, for example, $a+1 would give you a value of 2|3|4.
This feature is actually available in Perl5 as well through Perl6::Junction and Quantum::Superpositions modules, but without the syntax sugar (through 'functions' all and any).
At least for comparison (b < any(1,2,3)) it was also available in Microsoft Cω experimental language, however it was not documented anywhere (I just tried it when I was looking at Cω and it just worked).
You can't do this with native types, but there's nothing stopping you from creating a variable object (presuming you are using an OO language) which has a range of values or even a probability density function rather than an actual value.
You will also need to define all the mathematical operators between your variables and your variables and native scalars. Same goes for the equality and assignment operators.
numpy arrays do something similar for vectors and matrices.
That's also the kind of thing you can do in Prolog. You define rules that constraint your variables and then let Prolog resolve them ...
It takes some time to get used to it, but it is wonderful for certain problems once you know how to use it ...
Damien Conways Quantum::Superpositions might do what you want,
https://metacpan.org/pod/Quantum::Superpositions
You might need your crack-pipe however.
What you're asking seems to be how to implement a Fuzzy Logic system. These have been around for some time and you can undoubtedly pick up a library for the common programming languages quite easily.
You could use a struct and handle the operations manualy. Otherwise, no a variable only has 1 value at a time.
A variable is nothing more than an address into memory. That means a variable describes exactly one place in memory (length depending on the type). So as long as we have no "quantum memory" (and we dont have it, and it doesnt look like we will have it in near future), the answer is a NO.
If you want to program and to modell this behaviour, your way would be to use a an array (with length equal to the number of max. multiple values). With this comes the increased runtime, hence the computations must be done on each of the values (e.g. x+y, must compute with 2 different values x1+y1, x2+y2, x1+y2 and x2+y1).
In Perl , you can .
If you use Scalar::Util , you can have a var take 2 values . One if it's used in string context , and another if it's used in a numerical context .
I know that tan(angle) gets me the tangent. But how do I do the "reverse tangent" so that I can get the angle given the length of both sides of the right triangle?
I'm assuming there is a method for this in math.h?
As others have mentioned, atan() is what you're looking for. Generally, the operation is referred to as "inverse tangent" or "arc tangent", not "reverse tangent". The name "atan" comes from "arc tangent". There's also an atan2() function which takes both the X and the Y coordinates as separate paramters and will give you an angle relative to the 0 mark whereas atan() will leave figuring out the quadrant as an exercise for the developer. Beware, however, that the atan2() function on certain older MS environments (or maybe visual studio libraries?) doesn't work quite right...
There should be an atan() function.
For example: http://www.acm.uiuc.edu/webmonkeys/book/c_guide/2.7.html
use atan()