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.
dos "TYPE" command problem
Hi
You can see in the video that I have text file "hello" in "C:\Documents and Settings\Administrator". But when I try to access it using the "TYPE" command it fails. Could you please explain the reason for this failure?
The "type" command displays the contents...
Hello everyone
I hope you don't mind me asking a real silly question about the original evidence for dark energy. I've been reading about how Type 1a supernovae provided the initial evidence that the expansion of the universe was accelerating. They are able to do this because they are...
I am not sure which type of probability equation to use for the following problem:
A business has represented 3600 clients over a 20 year period with a 100% success ratio. The clients use a Special marketing program that increases their income without costing them money. The program uses a...
I am currently declared as a physics major and will be adding biology as a second major during the upcoming semester. I was originally set on astrophysics but the scarcity of post grad employment has me worried. Also astrophysics is a bit less "tangible" than neuroscience so I worry that I may...
I was playing around with the Schwarzschild interior solution when I came up with this interesting solution that I think would be fun exploring.
The interior solution for the uniform density case is given as:
\frac{d\tau}{dt}= \frac{3}{2}\sqrt{1-\frac{2M}{R}}-\frac{1}{2}\sqrt{1-\frac{2M...
I am almost a senior in high school (ya kinda early to be thinking about careers, but I can't help it) and I am utterly fascinated by engineering and physics. The only problem is that I don't really know what type of engineering I want to get into to satisfy my craving for knowledge.
I am...
We know there are (those mostly observable) fields like: gravity, forces between molecules, magnetic fields, electric fields, and infinite frequencies of electromagnetic fields, but:
What totally separate (special in a way), different by nature, totally new sorts of radiation or physical...
We have talked about black hole, Unruh and cosmological horizons in these forums...I am wondering if a simple example [thought experiment] might usher in an introduction to such rather abstract horizons:
the sphercial hollow shell of matter...from the outside, a test particle is attracted...
Bench Top's thread revived a number string curiosity that once stumped me. I wonder if anyone else saw anything like this before and can give the sequence a name.
Description
1. The sequence comprises only numbers from 1 to 2n.
2. Each number from 1 to 2n appears once and only once.
3...
I'm guessing it depends on how many factors/how unpredictable a subject is, what is it really? What makes mathematical finance so rigorous- requiring a phd in math/finance- while something like systems biology or pharmacokinetics only requires knowledge up to linear algebra?
I am not sure on this, so hope someone can shed some light on this. I asked this in the Astronomy forum, as someone told me to also ask here. I am not an expert in biology in any means :)
What type of organism was thought to be among the first on earth? I am not sure if this is the right way...
I am not sure on this, so hope someone can shed some light on this.
What type of organism was thought to be among the first on earth? I am not sure if this is the right way to ask this :)
Lets say if I wanted to see, or do tests on an organism, and my tests were related to doing tests on...
Hi everyone!
I just have a quick question about the theory behind a concept in statics.
Problem:
I was given a question that states that a sign is attached to a pin joint and also to a spring. The other end of the spring is attached to a spring joint as well. They hang there in static...
Hi, I've been reading a lot of journals lately for my dissertation, and I keep reading about certain types of antiferromagnetism. For example, the material I've been reading up on (Bismuth ferrite) is a G-type antiferromagnet and I have also seen A-type referred to in other journals. What does...
Now, I'm *not* advocating that such a government should be created. It's possible that such a government could be dystopian (although I don't think that it would be dystopian).
Of course, scientists are often at their most creative when they aren't stressed out, so it's important for them to...
Homework Statement
What type of hybridization occurs in the orbitals of a carbon atom participating in a triple bond with another carbon atom?
The Attempt at a Solution
I honestly thought it would be sp3 but it turns out to be sp. Can someone explain this to me? Thanks!
I know this is a silly question for a 12th grader to ask but I don't know the exact rules.
If we divide 950 by 121, the first digit of quotient is 7, then we place a decimal after 7 and bring one 0 down, which is correct way.
In the division of 21780/704, the first digit of quotient is 3...
Consider the following system (where B is a real number, B is not equal to 0),
x1' = -2x1 + (B+2)x2
x2' = Bx2
Depending on the value of B, the critical point at (0,0) can be of different type and/or stability. Describe the possible type/stability of the critical point for the different...
hi, with reference to my last post on oct 21,
https://www.physicsforums.com/showthread.php?p=2951801#post2951801
would anyone be able to tell me what the actual name or specification of the ceramic used in a peltier?
Cheers,
John.
I'd like to calculate the change in air pressure within a long tube - like the driveway hoses at gas stations.
The static pressure is zero, a vehicle drives over the hose and the increase in pressure activates a switch. I'm trying to determine the proper switch size (in PSI).
So, here is...
Can someone post a link to that website where you type in a sequence of numbers and it tells you the name of and descries the sequence and shows a formula if one exists.
Hello everyone,
What I just read is for type 1 diabetes mellitus, it requires an environmental factor (eg virus) and genetic determinant that allows the B cells to be detected as non self. Now I'm not very familiar with autoimmune diseases. My question is why does a virus have to come and...
This is related to a HW post I made over in the HW forum. I am stuck trying to find a more detailed formula for the Period-luminosity relationship of Type I Cepheids.
Wikipedias description doesn't seem to match with the book (or include any mention of type I or type II), and frankly the...
This is actually a example problem in the book. The homework problem is very related, but I some guidance on this particular part.
Homework Statement
A type I Cepheid has a period of 42 days and a apparent magnitude of 22. How far away is the star.
Homework Equations...
I want to hopefully go into graduate program in astronomy or experimental physics and am doing a dual Physics/EE major. I am going to try to get a job in a lab associated with the campus however it will probably be more geared towards applied physics and/or EE stuff than to fundamental physics...
Hello PFers, a chemistry question that I need help with awaits!
Homework Statement
10.42 Describe the types of bonds and orbitals in the following: (a) NO3-; (b) CS2; (c) CH2O; (d) FNO; (e) C2F4.
Homework Equations
The Attempt at a Solution
I tried to visualize the kind of...
Homework Statement
ok i am using Euler's way, i have to calculate "e"=2.718281828.
my script(see below) works but it only prints up to 4 decimal places, i have no idea why, help me please, thank you in advance.
Homework Equations
N/A
The Attempt at a Solution
function [eis] = euler1(in)...
I have always been fascinated by the kind of pictures linked below. Is there some particular name for this type of pictures? Googling 'christmas' took me to the linked ones.
[PLAIN]http://www.operationlettertosanta.com/Christmas%20images/Wallpapers/blue_christmas.gif
I think the...
Which type differential equation is this??
I simply can't recognize it
y' = \frac{1}{3}y^{\frac{1}{2}} + t^{\frac{1}{3}}
Which type of differential equation is??
non-linear?
Homework Statement
Consider a type I superconducting material with a parabolic coexistence curve separating the uniform superconducting and normal phases. H is the external magnetic field and T is temperature. Ignore the tiny magnetization of the normal phase. The critical field is
Hc = H0...
I'm currently in the middle of a decision that I have to bring to a conclusion very soon. Originally, my plan was to go to med-school, so I chose Biochemistry as my major, however during my senior year I realized that Medicine wasn't for me, and decided to get an education in Mechanical...
I have an interesting question.
I know it's unspoken that a rejection of financial aid is considered a "polite rejection" to your entire application, but what if I don't apply for financial aid?
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Maybe I'm biased because of the kind of projects I'm pursuing (raytracing), but I can't help feeling that for many areas, instead of defining a circle in terms of radians (or degrees for that matter), we should simply use unity and define say, a quarter of a circle as being 0.25.
Obviously a...
Hello
I currently hold a M.S. in Mechanical and Aerospace Engineering and a B.S. in Mechanical engineering (note the M.S. had an emphasis in controls and dynamics). I got my M.S. by only taking grad courses and have done no research or advanced project, I graduated last year and have been...
Hello,
I'm a former grad student with a Master's in Mechanical Engineering (emphasis on Dynamics and Controls) and I'm thinking of going back to school for a Ph. D. I'm very interested in technologies involving the use of endurance UAV's (UAV's designed to stay in the air for weeks at a...
I am a college physics grad. For many subtopics of precalculus or calculus, the following statement applies to me:
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My professor recently tasked me with first understanding maxwell's stress tensor and then applying it to analyze the force produced by a linear pull type solenoid.
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Hi!
May I know what type of this source code it is?It looks like assembly code, but I'm not sure.
LIST p=16f648a
include "P16f648a.inc"
__config h'3f18'
PC equ h'02'
cblock h'20'
endc
org h'0000'...
Hi,
During my research I came across a contour integral where the pole was on the boundary. I have never come across this before, do anyone of you know how I would go about computing this?
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What Be Your Nerd Type?
Here are my results. (The people that created this can't type)
Your Result: Science/Math Nerd
(Absolute Insane Laughter as you pour toxic chemicals into a foaming tub of death!)
Well, maybe you aren't this extreme, but you're in league with the crazy...
Homework Statement
Both {1,2}x Z+ and Z+ x {1,2} are well-ordered in the dictionary order. Are they of the same order type? Why or why not?
Homework Equations
To be of the same order type, we must be able to construct a bijection that preserves order, that is, x<y => f(x)<f(y)...
1. Homework Statement
A colorblind man with blood type AB marries a woman with normal vision and blood type A who is heterozygous for both traits. What are the odds of having a daughter that is colorblind and has blood type A?
2. Homework Equations
Xc Y IA IB x XC Xc IA i
3...
When solving for reactions in a 2D diagram as seen below, how does each type of joint affect the summation of forces in the x & y components?
My problem asks to find the summation of forces in the x & y components, and has a smooth pin connection in the left of the beam and roller on the right...
Let's say I'm testing anti-spam software. The number of false positives (aka, friendly messages misidentified as spam, for those who don't know the term) is 40. The number of false negatives (spam messages misidentified as friendly) is also 40. I'm testing 100 messages. How many more...
Hi
A friend of mine is doing an assignment on alternative sources of energy when he came across this site and sent the link to me:
http://www.crossfirefusor.com
From reading a couple of pages it seems deceptively simple and I'm told that the guy expects to get a net gain of a couple MW of...