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I'm looking for the module ChronoUnit
java.time.temporal.ChronoUnit
implementation in Python, found in Java 8.
The reason this modules is useful, is because it contains a procedure that computes the Days, Months, Years etc.. between to arbitrary dates.
PS: Implementing the date computation in python, can result in a lot of problems as there are a lot of corner cases that I simply have no time consider at the moment, so please be constructive while answering.
Edit: I think my question is not clear enough, but what I'm trying to accomplish is to be able to actually substract one date from another and as a result to get the months, days, years etc.. between the two.
As per juanpa.arrivillaga comment the arrow library provides a useful method that provides a near similar function, I think that I'll answer my own question now.
Thanks to #junpa.arrivillaga I figured out that the procedure might be easily implemented in python thanks to the arrow library.
The api to be used it the following:
arrow.Arrow.range('hour', start, end)
The final method in Python would be:
'''
Computes day, month, year s
between two dates.
frame - time frame
start - date start
end - date finish
This method only works if the generated timeframe between to dates
is finite, as Arrow.range returns a generator!
'''
def count_frame_between_dates(frame, start, end):
return len(list(arrow.Arrow.range(frame, start, end)))
Edit: Arrow.range returns a generator, in theory you can't compute the length of a generator, but if you are sure the generator you're using is returning a finite set of elements then you can convert this generato into a list then use len() to compute it's length.
Thanks to everyone.
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Pardon me if it's not the right place to post, but I'm so curious about this.
So December 5th is a date. Last year it fell on a Tuesday.
How can modulo be used to work this out?
I know this is a modulo problem, but just don't get how modulo is used here.
A famous algorithm for calculating the day of the week based on the date is Zeller's algorithm. If you follow that link to wikipedia, you will see the algorithm, which uses the modulus operator.
It is used to calculate the year of the century (denoted K) by doing
current year % 100
It's also used at the end of the expression, where we calculate modulo 7 of the formula shown on wikipedia:
https://wikimedia.org/api/rest_v1/media/math/render/svg/0f95195dcc0d98b351294277071736e97053324e
With a little intuition, you will realize 7 is used because there are 7 days in the week.
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So, my first app will be a personal one to help me meet deadlines. As you would imagine it is going to be very date oriented.
So, how do I grab the current date from my phone/emulator?
Bonus points if you can explain how to put it into an integer.
Any link or tutorial would be super great.
Thanks in advance.
You can get the time of your phone by creating a calender.
Calendar calendar = Calendar.getInstance();
This stores your actual time. If you want to get the date in a number, just us this:
long timeInANumber = calendar.getTimeInMillis();
You need to use a long instead of a integer, because this number is so big. A long is like a integer, but it can store greater values.
The number you get (called UNIX Timestamp) represents the count of milliseconds since 00:00 Janurary 1st, 1970.
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I have a java program which makes a JNI call. From java, I am sending Date.getTime() (basically seconds * 1000), and I expect C++ to convert it to a perfect date.
NOT DUPLICATE: I KNOW MANY SOLUTIONS EXIST ON STACKOVERFLOW, BUT NONE OF THEM SEEM TO WORK WITH DATES SINCE 01-01-0001
I need the dates to get perfectly generated, for as early as 01-01-0001 00:00:00.
Any clue or code snippet in C++?
This assumes that getTime() works according to the java docs outputting time since 1970.
Try this:
How can I convert seconds since the epoch to hours/minutes/seconds in Java?
(Edit: even though the question is for Java the implementation given in the first answer is in C, which is (mostly) valid C++ code. It doesn't account for leap seconds so just subtract the number of leap seconds since 1970 before evaluating)
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Though oracle technotes state that :
In Java SE 7 and later, any number of underscore characters (_) can
appear anywhere between digits in a numerical literal. This feature
enables you, for example, to separate groups of digits in numeric
literals, which can improve the readability of your code.
example : float pi = 3.14_15F;
is same as
float pi = 3.1415F;
But does it not become confusing to the developers working on code written by someone else?
Also does the use of underscore put any overhead on compiler or not?
But does it not become confusing to the developers working on code written by someone else?
Only if the developers don't understand the Java language! This construct has been been supported for long enough that every Java professional should recognize it ... even if they don't use it in their own code.
On the other hand, if your Java developers have not bothered to keep up to date with the new things in Java 7, they may be (temporarily) baffled. But the real solution is to educate your developers.
Also does the use of underscore put any overhead on compiler or not?
The overhead would be so small that it is impossible to measure.
There is no performance issue here.
The only time it would make any sense to use underscores is in a very large integer or with a binary integer. Like almost any bit of syntactical freedom the language provides, people are free to misuse it and write difficult to read code. I doubt this underscore thing will become a problem any more than the freedom to add extra white space is a problem.
The best example for when you would want to use this is with binary numbers where it is customary to place a space between every 4 bits.
For instance, compare:
int bitField = 0b110111011111;
int bitField2= 0b1101_1101_1111; //clearly more readable.
Other examples might include a credit card number or SSN as given in Oracle's documentation of this feature.
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Sorry if that title confused you its kinda hard for me to ask this without explaining it.
I am writing a (fairly) simple program to find the roots of a quartic (biquadratic) function.
My main question (I should know this >.>) is how do i get x in the quartic function (ax^4 * bx^3 * cx^2 * dx * e = 0) to stay as x and not be given a value. just sorta a place holder. this is part of it: ( b1 * x * c1 / 2 ); so i dont want x to be replaced. i just want it to stay as x and everything else around it multiply as you normaly would when solving the problem by hand.
My second question is from this site:
http://easycalculation.com/algebra/learn-quartic-equation.php
We haven't covered Quartics in school yet but We have covered cubics and quadratics so I know enough that i can follow a long for the most part except for right after it talks about the discriminant.
y2=(- term1 + r13*cos(q3+(2∏)/3) )
y3=(- term1 + r13*cos(q3+(4∏)/3) )
i dont get the parts with 2∏ and 4∏. If you know a simple way to explain it, please do :D if not i can always look it up and try to figure it out from there.
And my last question. I know how with the discriminant of quadratics depending on what it is depends on one root, no roots, or two roots. How does that apply with quartics and what should i do to check for that in my code (if you think i cant figure it out lol).
ummm i believe thats it. i can add info if needed. I dont think my code would be needed but i would prefer not to post it either way.
Thanks for the help.
-Ryan
The approach cited relies on a trigonometric identity described here used to solve cubic equations. The symbol ∏ is a capital π, or Math.PI in Java.
See also this example that uses org.jscience.mathematics.function.Polynomial and references a convenient root-finding algorithm.
The approach that you are looking for is called Symbolic Programming.
I do not, however, know of any stable Java libraries which allow for such programming.