In programming languages, a type system is a logical system comprising a set of rules that assigns a property called a type to the various constructs of a computer program, such as variables, expressions, functions or modules. These types formalize and enforce the otherwise implicit categories the programmer uses for algebraic data types, data structures, or other components (e.g. "string", "array of float", "function returning boolean"). The main purpose of a type system is to reduce possibilities for bugs in computer programs by defining interfaces between different parts of a computer program, and then checking that the parts have been connected in a consistent way. This checking can happen statically (at compile time), dynamically (at run time), or as a combination of both. Type systems have other purposes as well, such as expressing business rules, enabling certain compiler optimizations, allowing for multiple dispatch, providing a form of documentation, etc.
A type system associates a type with each computed value and, by examining the flow of these values, attempts to ensure or prove that no type errors can occur. The given type system in question determines what constitutes a type error, but in general, the aim is to prevent operations expecting a certain kind of value from being used with values for which that operation does not make sense (logic errors). Type systems are often specified as part of programming languages and built into interpreters and compilers, although the type system of a language can be extended by optional tools that perform added checks using the language's original type syntax and grammar.
So here is my dilemma. I have a test setup with multiple coils all lined up in parallel in such a way that one end of each coil is connected together while the other is connected to a switch (mosfet) the switches then connect each coil to ground but that ground can become + based on which coil...
Mathematics tends to be more progressive than any other field. But I've heard some people say that some math classes that they took were more difficult than the most advanced math classes that they took. For instance, I've heard people say that Calculus II is more difficult than Calculus III...
TL;DR Summary: ##(1+ \frac1x)^2 - (1-\frac1x)^2##
##(z+2)^2 -5(z+2)##
Upon simplifying the first I get ##\frac4x##. So isn’t the first expression fractional?
Upon simplifying the second I get a Quadratic expression.
When you study physics deeper you learn there are 4 types of atomic forces that represent all other in the atomic level (i.e. electromagnetic force, gravitational force, strong nuclear force, weak nuclear force).
I always try to see how they manifest in the the atomic interactions. For example...
##\sum_{n=1}^\infty n^{-a}## converge s for ##a\gt 1## - otherwise diverges. Is there any theory for ##a_n##? For example ##a_n\gt 1## and ##\lim_{n\to \infty} a_n =1##. How about non-convergent with ##\liminf a_n=1##?
Hey guys,
I got an XRD data for my sample and want to determine its density. This requires finding lattice parameters. However, I'm not certain about the crystallographic system of my sample. How can I determine the type of the unit cell my sample has from XRD data (I can use GSAS II if...
Hi there!
I have few years still without any solution.
I could find just only one exemplary of this bulb or lamp there I share pictures, this is exactly what I need to know what it is, brand or datasheet.
The base is E27.
AND the most important, In this VIDEO you can see the lamp...
Hi all
I have a question about this device in https://www.thingiverse.com/thing:2948680/files. Where can I find more information/reading material about this type of mechanical movement (for example, what is the ratio between the motor circle radius, pin location and the table bearings).
I wish...
Recently I've seen many fixed FR(or Wigner's friend) thought experiments.For example, https://arxiv.org/pdf/2011.12716.pdf is a zero-cited paper that presents a strenthened version of FR ,and claims to have solved its weaknesses.The author claims that it supports the idea that the "C"(for...
The following is given:
$$\displaystyle P(K = k) = \frac{1}{2}~\frac{\sqrt{2}~e^{-\frac{1}{2}~\frac{\left(k -\mu \right)^{2}}{\sigma ^{2}}}}{\sigma ~\sqrt{\pi }}$$
How can you prove that the following equalities are correct?
$$\displaystyle \sum _{k=-\infty }^{\infty }1/2\,{\frac {...
I was trying to paste the hosts file in this thread, and ran into an exception:
I can't paste the full error message from the console because PF is not allowing me to do so. Here is the error message:
Upon further testing, it turns out that I can paste the hosts file, but cannot type / etc...
There’s many types of problems in textbooks for example conceptual problems, problems where you’re given values and asked to find an unknown value and also problems that start with “show that..” “give x can you show y” “derive an equation in terms of…”
Im curious as to what type you like...
I have a 3 data column ##(X, Y, Z)## ranges from ##(min, max)##. For example,
##X = (0, 5)##, ##Y=(0, 3)##, ##Z=(0, 2)##. By using them I need to create a numpy array in the form of
##[(0, 0, 0), (0, 0, 1), (0, 0, 2), (0, 1, 0), (0, 1, 1), (0, 1, 2), (0, 2, 0)...]##
So in total there will be...
Given a gauge 25 (0.02" or 0.5mm) metal roof roll formed made from hot-dip galvanized cold rolled mild steel. How long can these thin metal roof melt in a typical house or office fire with typical fire load?
I read conflicting information. Some roof contractor said these thin gauge 25 metal...
We have this type of very famous nicely symmetric pde in our area. However, no one knows how to handle it properly since it is a nonlinear pde.
Suggestions on how it is called in general would help us further googling. I already tried keywords like "bilinear", "dual", "double", but by far could...
Hi,
*Excuse the crude visualization and possibly imprecise description - I'm not a rocket scientist :)
So, I have a friend that has come up with a "new" concept for a rocket propulsion design, and although I have a hunch that it might not work better than existing designs I cannot really...
A WC/WO star exploding within an expanding carbon-oxygen-neon nebula
https://arxiv.org/abs/2111.12435
https://www.wis-tns.org/object/2019hgp
https://www.universetoday.com/154116/a-new-kind-of-supernova-has-been-discovered/
https://ui.adsabs.harvard.edu/abs/2021TNSAN..76...1G/abstract...
A sinusoid can be described by the differential equation y'' = -k*y, where the force y'' is proportional to how far away from the center it is.
However in many physical systems the force between two bodies decreases with distance squared. So would we still classify the differential equation...
First suspicious activity of SN 2020tlf (in the NGC 5731 galaxy) was noted 130 days prior, which prompted astronomers to keep an eye on it.
"This is a breakthrough in our understanding of what massive stars do moments before they die," said lead study author Wynn Jacobson-Galán, a National...
If you're in a relationship (even if just on the shallow or acquaintance level), getting rejected by being ignored is the most painful experience. It hurts much more than being told your faults or where there is disagreement. Chats or even loud arguments are at least two-way. You are...
I ran into an issue of expressing certain types of operators and after a little thinking managed to do it by decomposing them with the help of a weird class of functionals:
$$|Φ⟩\rightarrowδ_{\{|Ψ⟩\}}(|Φ⟩)$$
for any state ##|\Psi\rangle##. And yes, it's a Dirac delta acting on the the Hilbert...
In ch. 13, pg.349 of Wald it's asked to prove that ##g_{AA'BB'} = \epsilon_{AB} \bar{\epsilon}_{A'B'}## is a Lorentz metric on ##V## (containing the real elements of the vector space ##Y## of type ##(1,0;1,0)## tensors). Given the basis ##t^{AA'} = \dfrac{1}{\sqrt{2}}(o^A \bar{o}^{A'} + \iota^A...
As far as I know, there is no object type in python. How it's determined?
For instance, we know that 2 is an object and it belongs to the int class. Similarly, 2.1 is an object, and it belongs to the float class. From my research, I have learned that data type ##\equiv## class. Then what the...
hi all,
Fairly old student here looking to go back and follow my life long dream of geting into physics. My goal is to eventually move into the study of theoretical physics, cosmology, that type of the stuff. So the things I am really interested in are Theory of Relativity, string theory...
Kindly see the attached problem below (i find the topic to be easy and straightforward). My concern is only on the highlighted part:
In my understanding, to define the type of correlation i have always approached a straightforward approach.
For value ##1## perfect positive correlation and...
I have recently become interested in automatic press machines, specifically an electro servo model. The press is capable of 5 tons (10,000 lb) of force. My question revolves around understanding what type of workbench I need to put this on top of.
I understand the workbench must at least be...
Hi all
I've long been a fan of the nrich site for maths and in recent years it has started to add a section on physics here. I also like IsaacPhysics although I haven't used it much in the past year so am still trying to get used to the new layout.
I'm looking for other resources along this...
hello. I am trying to calculaty flux in bioshield cell but i get zero (f44, f54) and i can't figure out the reason please help :) txt file is a part of the code
From what I have investigated, I know that dimples do a large part of the process of going far, and elasticity for sure is something of the main bounce thing, but things that confuse me like if the ball is empty affects both characteristics, or if the same dimples affect the bounce of the ball...
I'm confused. I have in my hand a 120VAC power cord with a standard 3 prong US plug on one end and a common IEC connector on the other (the type that plugs into a desktop computer for example). The IEC female end is labeld L, N and Earth. Hoever if I measure the voltage between the L and...
I have an abstract class template, BinNode<E> and another class template, BSTNode<Key, E>, which is derived from BinNode<E>. Here is the relevant pieces of code from each template:
template <typename E> class BinNode {
public:
virtual BinNode<E>* left() const = 0;
virtual void...
Typical box fan+air filter setups use axial consumer-grade fans designed for providing maximum air flow at low power consumption. These fans do not provide sufficient air flow at the high static pressure requirements typical of air filters. The air filters DIYers use are high Merv(e.g Merv 13)...
The book is asking me to write my own unique_ptr template (after just covering a bit about templates). I called my template single_ptr, and I gave it two template parameters, T and D. T is supposed to be the type that the raw pointer points to. D is supposed to represent a function type so that...
Hello.
If its possible I'd like to find out more about tidal locking for planets orbiting K type dwarf stars.
Specifically, at what distances from their host stars would exoplanets have to be to avoid becoming tidally locked. I'm specifying K dwarves because, from what I've read (see...
I had read that the Sun will become a white dwarf and then gradually cool down to a black dwarf, but this figure at Wikipedia says it will go supernova. (Yes, I know I should not trust Wikipedia, which is why I'm posting the question.)...
Hello,
In Python and other programming languages, data can be of different types: integer, float, string, Boolean. On the other hand, Data structures are containers of data items which can (or not) have the same data type.
A variable, when created, has:
a) name (a piece of data stored in...
I am looking at capacitor selection for a switched capacitor converter and I'm not sure which voltage rating to look for. I've was going to consider the DC rating since they're holding off a DC voltage, but they are subject to PWM excitation since they're switching between nodes at different...
I often encounter functions called "polynomial" in numerous fields. I don't see an obvious common trait other than that they're usually describing a real-valued continuous function. What aspects are typical or universal or distinct? What structures can be polynomial? Some sources say that...
Sometimes when I type and edit a post my editing actually overwrites what I have written and other times text is not overwritten but adds extra text. The first case makes editing harder. Is this something I have control over? I apologize if I have not made myself clear. Does it have something to...
As the brief summary explains, I'm looking for a linear actuator which moves quickly and can move a moderately low load (say, 10kg) but which also features an adjusting hard-stop which can withstand significantly heavier. So effectively, the actuator can move in and out, preferably quickly, but...
In section 1.12 Variational Approach to the Solution of the Laplace and Poisson Equations, Jackson mentions that in electrostatics, we can consider "energy type functionals". He gives, for Dirichlet Boundary Conditions,
$$I[\psi]=\frac{1}{2}\int_{V}\nabla\psi\cdot\nabla\psi d^3x-\int_{V}g\psi...
Hello i Tried to clean my activated carbon ,washed then put on oven then cool with water again. Is it possble to make anything other than CO2 this way? I read l type is something similar is that hazardous?
One hypothesis (may be a mainstream interpretation now, I didn't follow this subject very closely) about why "quantum communication" isn't possible using quantum entanglement is that we as observers, the physicists who conduct such experiments are automatons, and that at which instant would he...
Which type of letters is rule to use in aero-engineering when hand writing?
All capitals-block letters, cursive, upper and lower case-block letters. .?