Making Callout from Apex triggers
How can I edit this trigger to only fire once?
Floating point comparison Where can I download Windows 8 legally, from Microsoft? I ran across this problem in my Analysis class and can't seem to come up with a good solution. Here's the question: Show that if $\lim_{x\to a}f'(x) = A$ then $f'(a)$ exists and equals $A$. $f$ is continuous on $[a,b]$ and differentiable on $(a,b)$.  I tried applying the Mean Value theorem like this: There exists a $c \in (a, x)$ st $f(x)-f(a)=f'(c)(x-a) \implies \frac{f(x)-f(a)}{x-a}=f'(c) \implies f'(a)=\lim_{x\to a}\frac{f(x)-f(a)}{x-a}=\lim_{c\to a}f'(c)=A$  However, I think this is wrong. I am pretty sure the Mean Value theorem is needed, but my application of it seems to be incorrect. Would somebody be able to point me in the right direction? Plot Option Precedence while combining Plots with Show[] In reading about the  protocol I noticed how much its proofs-of-work apparently depend on  of the SHA-256 hash function. And so  presumably do many other applications.  How do researchers go about proving uniformity of proposed hash functions? Is it just an empirical matter of running many inputs through the function and observing the distribution of outputs, or can one formally prove the property? Where could one (non-crypto-expert) learn about how such proofs are constructed and look one up e.g. for the case of SHA-256? How to find and delete identical points? I recently performed  on a merged point feature class in ArcGIS 10.1.  I specified "1 meter" XY tolerance for the Integrate command.  The resulting point feature appears to be what I want except points that were integrated are now stacked on top of each other, which will be problematic in future processing steps.  The attributes for my dataset consist of an OID, Shape, x, y, z.  Where x and y = UTM coordinates and z = buffer distance.  The command  does not appear to work for my dataset (i.e based on Fields: OID, Shape, x, y, z and XY tolerance = 1m) as the output still has stacked points.  I am also working with big data--the integrate output has 37 million points.    There is a related thread, titled , although I would like to open the question up to python solutions too.  What is the best way to find and delete (spatially) duplicate points?  Is there a better solution to integrating such that the output does not contain overlapping points? Ubuntu installation is slow, why? Adverb between conjugated verb and infinitive? Recommendations for Numerical Analysis texts? I'm in a numerical analysis course right now and it's pretty rigorous but I'm enjoying it a lot. I took a lower level course before that was more oriented towards implementation of numerical methods, so it's not my first time with the material.  Anyway, my professor wrote his own course notes and they're fantastic but I wanted some reference material since I'm currently outlining my own notes. Just wondering what the big ones out there are  edit: I would say I'm at an advanced undergraduate level Normal subgroup of prime index If $\sum_{n=1}^{\infty} a_n$ converges, then so does $\sum_{n=1}^{\infty} a_n^{\frac{n}{n+1}}$ Given a positive sequence $(a_n)$. Prove that if $\displaystyle \sum_{n=1}^{\infty} a_n$ converges, then so does $\displaystyle \sum_{n=1}^{\infty} a_n^{\frac{n}{n+1}}$.   I tried to use the root test, and I was stuck with the case $\lim \sup \sqrt[n]{a_n}=1$. Maybe we need some trick here.  Thanks so much. Proof that the Casimir invariant of a representation commutes with everything Trying to attach a file from SD Card to email I am trying to launch an Intent to send an email. All of that works, but when I try to actually send the email a couple 'weird' things happen.  here is code   Intent sendIntent = new Intent(Intent.ACTION_SEND); sendIntent.setType("image/jpeg"); sendIntent.putExtra(Intent.EXTRA_SUBJECT, "Photo"); sendIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse("file://sdcard/dcim/Camera/filename.jpg")); sendIntent.putExtra(Intent.EXTRA_TEXT, "Enjoy the photo"); startActivity(Intent.createChooser(sendIntent, "Email:"));   So if I launch using the Gmail menu context It shows the attachment, lets me type who the email is to, and edit the body &amp; subject. No big deal. I hit send, and it sends. The only thing is the attachment does NOT get sent.  So. I figured, why not try it w/ the Email menu context (for my backup email account on my phone). It shows the attachment, but no text at all in the body or subject. When I send it, the attachment sends correctly. That would lead me to believe something is quite wrong. Do I need a new permission in the Manifest launch an intent to send email w/ attachment? What am I doing wrong? Prove $4(x + y + z)^3 > 27(x^2y + y^2z + z^2x)$ Prove that, for all positive real numbers $x$, $y$ and $z$, $$4(x + y + z)^3 &gt; 27(x^2y + y^2z + z^2x)$$  I've tried expressing it as a sum of squares, but haven't got anywhere.   Hints are also welcome. Is there a JavaScript equivalent of Java's class.getName()? Are there any advanced options for Google Chrome's history search? Why should I use the keyword "final" on a method parameter in Java? How can I iterate, loop, process, or otherwise do something, with each element from a comma separated list of things?  This question       , and the are already lots of very good answers everywhere. However I think it would also be valuable to have a single reference point where all such alternative techniques are explained in detail, with their advantages and disadvantages discussed.  All of plain-TeX, LaTeX, LaTeX3, LuaTeX, Context, etoolbox, pgffor, etc. answers are invited. Please consider explaining, for example:   How does the command/method deal with whitespace around items? How does the command/method deal with empty/missing items? (e.g. a,b,,c) How does the command/method deal with a trailing comma? Can the command/method work of a list stored on a macro? Is each iteration evaluated globally or on a local group? (i.e., if a command is defined during an iteration, does the command survive the loop?) Do items get expanded or somehow mangled before being processed? What about lists where items are key=value or some other kind of pairs? Does the method work for lists separated with something other than a comma? Any other thing I should know before deciding to use this method? Is it safe to put hot food in the fridge? I heard that putting really warm food in the fridge right after cooking it is not the right thing to do. It might cause bacterial growth? Is this true? Abelian groups of order n. Is there a number $n$ such that there are exactly 1 million abelian groups of order $n$?   Can anyone please explain. I would yes because numbers are infinitive, and so any number n can be expressed as a direct product of cyclic groups of order n.  Can anyone please help  me understand.  Thank you.