Being a hobbyist coder and influenced by , I tend to organize the data I'm working with. Helping my little sister on her English made me curious about something.  Tenses in English is usually listed/grouped as    Simple   Past Simple Present Simple ...  Progressive/Continuous Perfect Perfect Progressive   or   Past   Past Simple Past Progressive ...  Present Future   You get the idea. They're either grouped by tenses or aspects. I like the latter, grouping them by tenses. So, one would get, for present tense   Present   Simple Progressive Perfect (Simple?) Perfect Progressive    Now, this grouping doesn't seem satisfactory. I'd group it as   Present   I   Simple Progressive  II (Perfect)   Simple Progressive     which makes a lot more sense to me. Though this grouping creates ambiguity, that is "I".   My question is what is the difference between "I" and "II"? What would one name "I", since "II" is the Perfect aspect. What exactly is "Perfect" and how it differs from "I"?    PS: I live in Turkey, so English isn't my native language. This categorization helps me internalize tenses better. Structured data is always easier to comprehend. I've seen a lot people (mostly classmates) struggle with Tenses, even after years of education. Discarding other possible reasons, this insufficient categorization is one of the reasons of the struggle, I think.  My reasoning in this grouping might be wrong. If so, you should ignore that. My question at its core would be 'If "II" is the Perfect aspect, which it is, what would be "I"? What should I name it?'  I'm fine with learning the right thing using the wrong method, as long as it works and makes sense to me. (You know, assuming my grouping is absurd.)
Non-na­tive speak­ers of­ten get con­fused about what the var­i­ous tens­es  and as­pects mean in English. With in­put from some of the folk here I've put to­geth­er a di­a­gram that I hope will pro­vide some clar­i­ty on the mat­ter.  I of­fer it as the first an­swer to this ques­tion. Con­sid­er it a liv­ing doc­u­ment. In­put is wel­come, and good sug­ges­tions will be  in­cor­po­rat­ed in­to the di­a­gram.    No­ta bene: What this is not is a dis­cus­sion of whether there are  more than two tens­es in English. , to which this ques­tion is not in­tend­ed to sup­ply ar­gu­ments one way or the oth­er.  Here, the aim is to pro­vide an overview of what con­struc­tions English-speak­ing peo­ple use for con­vey­ing in­for­ma­tion about ac­tions re­fer­ring to past, present, and fu­ture, and to pro­vide it first and fore­most to pre­cise­ly the peo­ple who are like­ly to use "tense" as a catch-all term in their search, rather than to lin­guists who know bet­ter.  Break­ing News There is now an ex­cel­lent ELU blog ar­ti­cle ti­tled  . It is high­ly rec­om­mend­ed read­ing.
I want to upgrade my Ubuntu 13.04 to Ubuntu 13.10. I'm unable to do via GUI.   [ The reason why I'm unable to do so:  Via software updater, I proceed ahead and click upgrade (for upgrading my OS). I authenticate by providing my password. Then it proceeds and downloads upgrade tool. That time only (while downloading the tool) error message comes "system program problem detected". It then doesn't proceed ahead and I click to report the problem ]  So, I tried via command line but here also I couldn't succeed upgrading my OS.  For the same I ran   $ sudo apt-get update   Then I ran  $ sudo apt-get dist-upgrade   And then:  ravbholua@ravbholua-Aspire-5315:~$ sudo do-release-upgrade Checking for a new Ubuntu release Get:1 Upgrade tool signature [198 B]                                                                                                  Get:2 Upgrade tool [1,135 kB]                                                                                                         Fetched 1,135 kB in 6s (32.9 kB/s)                                                                                                    authenticate 'saucy.tar.gz' against 'saucy.tar.gz.gpg'  gpg exited 2 Debug information:    gpg: Signature made Friday 01 November 2013 10:34:27 AM IST using DSA key ID 437D05B5 gpg: Can't check signature: public key not found  Authentication failed Authenticating the upgrade failed. There may be a problem with the network or with the server.  ravbholua@ravbholua-Aspire-5315:~$    Please suggest how to go ahead and upgrade my OS. HTTP vs HTTPS performance Are there any major differences in performance between http and https?  I seem to recall reading that HTTPS can be a fifth as fast as HTTP.  Is this valid with the current generation webservers/browsers?  If so, are there any whitepapers to support it? How can I dual boot Windows and Ubuntu? I want to filter a java.util.Collection based on a predicate. R-squared: X "explains" the percentage of variation of the Y values. Does axis order matter? If my question gets migrated to another site, is it possible somehow to reverse it back to the original site? Overriding some DNS entries in BIND for internal networks It confuses/blows my mind that the Binomial has variance proportional to $p(1-p)$. Equivalently, the Fisher information is proportional to $\frac{1}{p(1-p)}$. What is the reason for this? Why is the Fisher Information minimized at $p=0.5$? That is, why is inference most difficult at $p=0.5$?  Context:  I'm working on a sample size calculator, and the formula for $N$, the sample size needed, is an increasing factor of $p(1-p)$, the result of a variance estimation in the derivation. Difference between  and  in Java Capturing speaker output in Java Colors in Photoshop CS6/CC look different than in browser? One of my friends, a graphic designer told me recently that sometimes colors in Photshop look slightly different than the ones rendered in browser.  I know it is possible when you save a file and then use it on a website due to palettes, but he uses given color in PS, for example #b81e1e, then he creates a DOM element and sets its background to #b81e1e and the color is rendered differently in browser than in PS (I guess it's not that subtle as he can easily spot it). It's not a regular thing and it doesn't happen always, but he states it happened to him a few times, although he can't really tell me with witch colors.    Is it even possible? Because I have never really heard about anything like this &amp; nothing like this ever happened to me... What causes javac to issue the "uses unchecked or unsafe operations" warning For example:  javac Foo.java Note: Foo.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. How to Toggle Selected Objects Visibility with H shortcut as in Maya I want to be able to toggle the visibility of selected objects with a shortcut (H) the way you can do in Maya and XSI, shown in the GIF. I'm guessing scrippting is needed. I've tried to do it my self but I'm new to Python and Blender and as soon as the objects are hidden they seem to no longer be in a selection state/list. Eg if I manually select the hidden object/s in the Outliner and try to print the selected object to the console, none seem to be selected. Is this possible to do with the current state of Blender 2.8? Use biblatex and utf8 For my thesis, I use biblatex for the bibliography.  As seen , biblatex is not compatible, with \usepackage[utf8x]{inputenc}. It was reported as close but I still have the same problem with my version of bibtex (last one on archlinux ). I want to use the € symbol inside my report but it fails without utf8.  ! Package biblatex Error: Incompatible package 'ucs'.  See the biblatex package documentation for explanation. Type  H &lt;return&gt;  for immediate help.  ...                                                l.7 \begin{document}   Any idea idea how to fix ?  \documentclass{report}  \usepackage[utf8x]{inputenc} \usepackage{biblatex} \bibliography{includes/mybib}{}  \begin{document}  X said Y \cite{bib1}  \printbibliography  \end{document}   and the file mybib  @online { bib1,        title = {Refrence title},        author = {X},        url = {http://site.com/y}} Trying to install ubuntu on a laptop. The "bios/uefi" has no uefi boot options &amp; the windows boot manager just kicks in. The only "option" is "boot from hard disk". So we tried to use efibootmgr to put grub to boot first.  When we run an efibootmgr -o xxxx,xxxx,xxxx command it seems like the order gets fixed but on reboot the windows boot manager still has control, then when we re-opened the live usb &amp; checked the boot order it remains unaffected.  What are other ways to change the efi boot order? Maybe by mounting the efi partition (in mnt) and doing what? Checking the maximality of a principal ideal in $R[x]$ Let $R = \mathbb{Z}_{(2)}$ be the localization of $\mathbb{Z}$ at the prime ideal generated by $2$ in $\mathbb{Z}$. Then prove that the ideal generated by $(2x-1)$ is maximal in $R[x]$. Show $f(x)=x\ln x$ is not uniformly continuous Show $f:(0,\infty)\rightarrow \mathbb{R}, f(x)=x\ln x$ on $(0,\infty)$ is not uniformly continuous.    I think that the general way to prove that something is not continuous in a metric space is to let $\epsilon=...$ and show that $\forall\delta&gt;0$, $d&#39;(f(x)-f(y))&gt;\epsilon$. I can't use the Mean Value Theorem because we haven't gone over it yet.    Here's an attempt: Let $\epsilon=1$. Without loss of generality, let $x&gt;y&gt;0$. $|x\ln x-y\ln y|&lt;|(x-y)(\ln x)|\leq|x-y||\ln x|$...$\delta=\frac{\epsilon}{\ln x}$ and therefore doesn't work for all $x$? I am trying to plot the function 1/x^2 but the result is obviously wrong, here is how it looks like    here is the code  \begin{center}      \begin{tikzpicture}      \begin{axis}[      %xlabel=$x$,     %ylabel={$f(x) = x^2 - x +4$}   ]      \addplot[blue] {1/(x^2)};     \end{axis}     \end{tikzpicture} \end{center}   Any suggestions on how to fix this? For my MAC laptop, I only have 250GB and out of this 250GB MAC is taking up 129GB in the other section. I looked everywhere to the best of my knowledge. Please note my home directories is only 45GB. Can you somehow please help me? How to mix three different shaders on the same material?