I have written a function using the DO macro (using  Peter Seibel's book as reference) but for some reason, when I compile my function:  (defun test ()   (do ((n 2 (1+ n))        (m 1 (1+ m))        (a (1+ n))        (b (1+ m))        (c (+ n m)))       ((= n 10) (* a b c))       (print (* a b c))))   I get the following warning messages:  WARNING: in TEST in lines 1..10 : N is neither declared nor bound,          it will be treated as if it were declared SPECIAL.  WARNING: in TEST in lines 1..10 : M is neither declared nor bound,          it will be treated as if it were declared SPECIAL.  WARNING: in TEST in lines 1..10 : N is neither declared nor bound,          it will be treated as if it were declared SPECIAL.  WARNING: in TEST in lines 1..10 : M is neither declared nor bound,          it will be treated as if it were declared SPECIAL.   When I try to execute test, it says that n has no value.   I am under the impression that the order of binding doesn't matter, but I tried rearranging it anyway and still received the same result.  What am I missing here?  I am using CLISP 2.49
I understand the difference between LET and LET* (parallel versus sequential binding), and as a theoretical matter it makes perfect sense.  But is there any case where you've ever actually needed LET?  In all of my Lisp code that I've looked at recently, you could replace every LET with LET* with no change.  Edit: OK, I understand why some guy invented LET*, presumably as a macro, way back when.  My question is, given that LET* exists, is there a reason for LET to stay around?  Have you written any actual Lisp code where a LET* would not work as well as a plain LET?  I don't buy the efficiency argument.  First, recognizing cases where LET* can be compiled into something as efficient as LET just doesn't seem that hard.  Second, there are lots of things in the CL spec that simply don't seem like they were designed around efficiency at all.  (When's the last time you saw a LOOP with type declarations?  Those are so hard to figure out I've never seen them used.)  Before Dick Gabriel's benchmarks of the late 1980's, CL was downright slow.  It looks like this is another case of backwards compatibility: wisely, nobody wanted to risk breaking something as fundamental as LET.  Which was my hunch, but it's comforting to hear that nobody has a stupidly-simple case I was missing where LET made a bunch of things ridiculously easier than LET*.
Proving $6^n - 1$ is always divisible by $5$ by induction I'm trying to prove the following, but can't seem to understand it. Can somebody help?     Prove $6^n - 1$ is always divisible by $5$ for $n \geq 1$.   What I've done:  Base Case: $n = 1$: $6^1 - 1 = 5$, which is divisible by $5$ so TRUE.  Assume true for $n = k$, where $k \geq 1$: $6^k - 1 = 5P$.  Should be true for $n = k + 1$  $6^{k + 1} - 1 = 5Q$  $= 6 \cdot 6^k - 1$  However, I am unsure on where to go from here. linux command to prevent dos attack by using netstat and iptables I want to DROP more than 200 requests per ip to prevent ddos attack. this is command that i used to detect requests count per ip :  netstat -alpn | grep :80 | awk '{print $5}' |awk -F: '{print $(NF-1)}' |sort | uniq -c | sort -nr   now i want add all ip addresses that made more than 200 requests into IPtables to DROP input and out put. What is the main difference between an inner class and a static nested class in Java? Does design / implementation play a role in choosing one of these? I have been working with a string[] array in C# that gets returned from a function call. I could possibly cast to a Generic collection, but I was wondering if there was a better way to do it, possibly by using a temp array.  What is the best way to remove duplicates from a C# array? Radeon error atombios stuck in loop The screen goes blank and shows logs me out immediately a while after using multiple monitors.   dmesg shows:  [33786.908877] [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [33786.908901] [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing 6DD2 (len 254, WS 0, PS 4) @ 0x6DE0 [33786.908910] [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing 673E (len 78, WS 12, PS 8) @ 0x6777   lspci | grep -E 'VGA|Display' shows:  00:02.0 VGA compatible controller: Intel Corporation HD Graphics 5500 (rev 09) 03:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] Sun  XT [Radeon HD 8670A/8670M/8690M / R5 M330 / M430] (rev 83)    explains exactly my situation. But I don't have /etc/modprobe.d/radeon.conf file. Can we have a way to access Area 51 on the iOS and android app?  More sites would flourish due to more traffic. Limits involving factorials $\lim_{N\to\infty} \frac{N!}{(N-k)!N^{k}}$ I am trying to calculate the following limit  $$\lim_{N\to\infty} \frac{N!}{(N-k)!N^{k}}$$ where $k$ can be any number between $0$ and $N$.  I thought of the following:  If I take the logarithm of the expression then I get:  $$\lim_{N\to\infty} \left(\log(N!)-\log((N-k)!)-k\log N\right)$$    Using the Stirling formula this can be approximated as:  $$\lim_{N\to\infty} \left(N\log(N)-(N-k)\log(N-k)-k\log N\right)$$  Now there are two cases: If $k$ is $N$, then the second term vanishes and the remaining terms cancel. If $k$ is smaller than $N$, then I can drop the $k$ inside the second logarithm and all the terms cancel. So the limit $$\lim_{N\to\infty} \log\left(\frac{N!}{(N-k)!N^{k}}\right)=0$$ Which means that: $$\lim_{N\to\infty} \frac{N!}{(N-k)!N^{k}}=1$$ I don't know if this is mathematically rigorous. Would like some help. Thanks What's a recommended alternative to Quickbooks pro? I've just installed Ubuntu to replace Windows. I can't seem to find a good alternative to  to run on Ubuntu. Any help would be appreciated. indefinite article before proper names Kafka, discovered in the 1920s by the Expressionists, damned by the Nazis in the 1930s and by the Marxists at more or less the same time, was reinvented after World War II by the French Existentialists. They saw in him the father of Angst and the Angst for the father: an Albert Camus before his time.   Can you tell me what the purpose of using the indefinite article before the proper name is in the sentence above. What it be a mistake to write just "Albert Camus" without the article? Evaluate the sum: $\sum\limits_{n=0}^{\infty} \frac1{F_{(2^n)}}$ Evaluate the sum:  $$\sum_{n=0}^{\infty} \frac{1}{F_{(2^n)}}$$  where $F_{m}$ is the $m$-th term of the Fibonacci sequence. I need some support here. Thanks. Was drafting an email and my senior wanted to type "Planting saplings is our way of saying we care for our Nature". I felt that's wrong English. Shouldn't it be "we care for Nature"? (it makes it a bit impersonal to remove the 'our', but if 'our nature' isn't right, can the cuteness factor of mentioning 'our nature' be preserved?. Which is correct?) Let the ring of fractions be denoted as $S^{-1}R$.       Proposition (from Robert Ash's textbook "Basic Abstract Algebra")      Define $f: R \rightarrow S^{-1}R$ by $f(a) = a/1$. Then f is a ring homomorphism. If S has no zero divisors then f is a monomorphism, and we say that R can be embedded in $S^{-1}R$. In particular:      (i) A commutative ring R cna be embedded in its complete (or *full) ring of fractions ($S^{-1}R$, where S consists of all non-divisors of zero in R).       (ii) An integral domain can be embedded in its quotient field.    Why does the proposition say "If S has no zero divisors..."? If S really had zero divisors, then this wouldn't even be properly defined, right? Because we would have a/0 for some a in R. How do I check if an object has a key in JavaScript? Which is the right thing to do?  if (myObj['key'] == undefined)   or  if (myObj['key'] == null)   or  if (myObj['key']) Replacing a font in many illustrator files I have several hundred Illustrator files that are formatted similarly, and for legal reasons I need to replace a font in all of them. Even with the 'Find font' tool, that's a hell of a lot of fonts to replace by hand.  Is there some way of automating it? For example, using Bridge? Illustrator (CS5) doesn't offer many options in Bridge, compared to the automation options offered by Photoshop. I also don't see any option for running actions on multiple Illustrator files.  Also, creating a repeatable action for replacing the font doesn't seem to work: instead of repeating my action, it brings up the dialog box an waits for me to tell it to replace them.  As a programmer I'm prepared to edit the files directly if it can be done without breaking them.    Update: The 'Batch...' menu item from Illustrator's actions panel menu allows the same action to be performed on a folder of files. It doesn't fix the Find Fonts action waiting for input though. Toggling the dialog off makes the action do nothing at all. Is it possible to recover original content from an edited image file? OK possibly a random question here, but one that is relevant to the site and regarding a hot topic nowadays: privacy.  If I load an image file (in my case a PNG photocopy of a document which contains some personal details) into Gimp, and I 'fill' with black (i.e. as if to redact) the areas of the image that contain sensitive information, and I then overwrite the original file, is there any way that the original untouched image can be recovered or gleamed? Such as low level bit analysis or...?  If so what tools and techniques are behind that, and how can I mitigate this? Is it a simple case of not overwriting the original but simply creating a new file with the changes? Are there fixed size integers in GCC? On the MSVC++ compiler, one can use the __int8, __int16, __int32 and similar types for integers with specific sizes. This is extremely useful for applications which need to work with low-level data structures like custom file formats, hardware control data structures and the like.  Is there a similar equivalent I can use on the GCC compiler? Convert a javascript associative array into json object using stringify and vice versa Console freezes on auto-complete of /mnt/folder (CIFS) share I have a Ubuntu 14.04 server that will lock up after an undetermined amount of time when you attempt to tab-auto-complete the path of a CIFS share in the /mnt directory. I mount the share and it seems to work fine for a uncertain amount of time. I can do ls or run du on folders within the mounted share. Then I will go to tab out a folder path and my console locks up. I can start a new session but it will lock as soon as I try to mess with the mounted share; this even happens to other users if I have them try as well. I have no idea why this is happening? I've never seen this issue. py2exe - generate single executable file Evolution threads extra lines before signature