So I came across this question sometime ago and couldn't figure out the question for it, but it left me wondering as to why it works. I don't have the question in front of me, but I'll try my best to repeat it from memory.  Why are the outputs of these two pieces of code the exact same in C? One of them is obviously wrong.  Code 1:  int main() {    int a;    int b[] = {1,2,3,4};    for(a = 0; a&lt;4; a++)       printf("%i\n",b[a]);    return; }   Code 2:  int main() {    int a;    int b[] = {1,2,3,4};    for(a = 0; a&lt;4; a++)       printf("%i\n",a[b]);    return; }   The output of both pieces of code is:  1 2 3 4   Someone told me it has something to do with a stack and memory locations, but the explanation wasn't clear enough. Can anyone help explain this more clearly?
As Joel points out in , in  (aka: K &amp; R), there is mention of this property of arrays in C: a[5] == 5[a]  Joel says that it's because of pointer arithmetic but I still don't understand. Why does a[5] == 5[a]?
The only solution that I have been able to come up with is $d=1$, but because $d&gt;2$, I can't seem to figure out how to find a solution. Empty vector menu in QGIS on PC with French as default language I installed QGIS 3.0.0 on a PC with French as default language. After changing the language of QGIS to English, the 'Vector' menu is empty and there is a French 'Vecteur' menu. Any ideas how to fix this? I cannot change the system language. Check if a services is installed using C I want to have an index entry typeset as $a_\text{T}$, so I issue the command \index{at@$a_\text{T}$}. Each use of this index command creates a separate line in the index. How can I get \makeindex to recognize they all reference the same topic?  My index entries look like this: What is the purpose of the first test in an inductive proof? Learning about proof by induction, I take it that the first step is always something like "test if the proposition holds for $n = \textrm{[the minimum value]}$"  Like this:       Prove that $1+2+3+...+n = \frac{n(n + 1)}{2}$ for all $n \ge 1$.   Test it for $n = 1$:  $$n = \frac{n(n + 1)}{2} \implies 1 = \frac{2}{2}\textrm{, which holds.}$$  * The rest of the proof goes here *    So, I do it all the time (like a standard). But I never really thought about why. Why do I do such test? I can see that if the test does not hold, it cannot be proven by induction, I guess. But is there another reason we do this? I have a new laptop which I am setting up as dual boot Windows/Linux.    I would like to access files from both Ubuntu and Windows 7.  Should I create a separate NTFS partition? Find out which process is locking a file or folder in Windows Failed to Login : Invalid session (Try restarting your game) Minecraft Error When I try to connect to servers or join up on lan worlds in Minecraft it says "Failed to Login : Invalid session (Try restarting your game)". Multiplayer used to work fine but now keeps coming up with this error. Can anybody help? Let $C$ be the coefficient of $x^2$ in the expansion of the product $(1 - x)(1 + 2x)(1 - 3x)\cdots(1 + 14x)(1 - 15x).$ Find $|C|.$   Just to begin,  $(1-x)(1+2x) = -2x^2 + x + 1$  $(1-x)(1+2x)(1-3x) = 6x^3 - 5x^2 - 2x + 1$   But expanding on like this take too long.  In the end the terms will be like:  $(1 - 15x)(a_0 + a_1x^1 + a_2x^2 + ....)$  Then just looking at the $x^2$, it will be:  $(a_2x^2 - 15a_1x^2) = x^2(a_2 - 15a_1)$  But it it still a very hard problem, any hints? UK visit visa: What documents prove genuine relationship with the visitor? Prove that $ AB$ is a subgroup of order $mn$ if $m$ and $n$ are relatively prime. Assume $f:\mathbb R\rightarrow  {\mathbb R} $ is Lebesgue integrable, prove $\sum_{n\in\mathbb N } f(x+n)$ converges for almost everywhere x. This is a question discussed with friends. Thanks Why does the order of parameters matter for sp_trace_create? difference fn(String... args) vs fn(String[] args) Whats this syntax useful for :       function(String... args)   Is this same as writing       function(String[] args)    with difference only while invoking this method or is there any other feature involved with it ? Monotonicity of the sequences $\left(1+\frac1n\right)^n$, $\left(1-\frac1n\right)^n$ and $\left(1+\frac1n\right)^{n+1}$ Should I use 'or' or 'nor' after a negative statement? This document does not cover the SDK interfaces nor any other reference material.   I think the above is correct, but my grammatical checker in Microsoft Word underlines nor and suggests or. Why? In MK (Morse-Kelley) set theory life is easy: $\forall X\forall y\left(y\in\bigcap X\leftrightarrow\forall x\left(x\in X\rightarrow y\in x\right)\right)$. If $X=\left\{\right\}$ then $\bigcap X=U$, where $U$ is the universal class. So the (unary) intersection of the empty set is the class that contains all sets as elements. In ZF (Zermelo-Fraenkel) set theory, instead, proper classes are not allowed. So, how can I define $\bigcap X$ in ZF? I tried with the following definitions:   $\forall X\left(X\not=\left\{\right\}\rightarrow\forall y\left(y\in\bigcap X\leftrightarrow\forall x\left(x\in X\rightarrow y\in x\right)\right)\right)$. This means that $\bigcap\left\{\right\}$ is undefined, which is not that good. $\forall X\forall y\left(y\in\bigcap X\leftrightarrow X\not=\left\{\right\}\land\forall x\left(x\in X\rightarrow y\in x\right)\right)$. This means that $\bigcap\left\{\right\}=\left\{\right\}$, which is the opposite of MK.   I couldn't find any other valuable definition. Any ideas? Thank you. Difference between standard error and standard deviation I'm struggling to understand the difference between the standard error and the standard deviation. How are they different and why do you need to measure the standard error? Cycles Normal Bake does'nt bake indents that are not tapered I can bake high poly normal maps with a lot of success, however if I try to bake a very simple indentation on a cube with no tapering I get a flat baked normal map, please see the below image to clarify what I mean.   I dont know I am doing wrong because if I scale down the indented face slightly it will bake the normal map correctly, as seen in the image below. If a group satisfies $x^3=1$ for all $x$, is it necessarily abelian? I know that any group satisfying $x^2=1$ for all $x$ is abelian. Is the same true if $x^3=1$? I don't think it is, but I can't find a basic counterexample.