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I have to compute these special functions. They have been a part of my life off and on for many years. I wrote a few C# routines for that. The trouble is I need fairly large indices. When I compute them my only control is graphic representation, observing them visually and making sure that they "behave decently." There is another way too, to use different path in recurrence formulas to compute the same function, thus arriving at the function from a different direction. Sometimes I use the double factorials which might be also error prone in some areas because you end up handling huge numbers. In many cases it is iterations over and over again, driving the indices up and up.
What are standard, mathematically correct ways to estimate computational errors in such situations. Where can I find them?
Thanks, -- AboutFace 22 ( talk) 16:16, 17 March 2014 (UTC)
Thank you. Parts of it I have known for years, some of that is new. I can tell you that I had been complacent with my calculations more or less until I checked this. It is a Casio online calculator for Associated Legendre Polynomials. When you increase index n the functions take a totally bizarre shape. Mine behave much, much better. There is another website which I cannot immediately find which makes an error estimate for their code and it is discouraging. Thanks, --- AboutFace 22 ( talk) 18:57, 17 March 2014 (UTC)
Thank you very much. There is a lot of stuff out there when one starts digging. -- AboutFace 22 ( talk) 21:52, 17 March 2014 (UTC)
I need to cut a passage from a song for class presentation. I have the song in MP3 format; what (free?) tool/program should I use to cut the passage and save it as an MP3? Thanks, Drmies ( talk) 17:27, 17 March 2014 (UTC)
I am an old C programmer. C is not perfect but I can make it do whatever I need done. I've been running into C++ for years. I have made a couple of attempts to understand it, but without much success, meaning I don't instantly see how to structure a new program in C++. There are a few little things that C++ introduced that I like, like the double slash comments and the ability to declare variables within blocks below the procedure level, but these don't really touch on C++'s raison d'etre. I have read some explanations of C++ and they list a bunch of things that C++ does, but I fail to see how any of these features translate into any kind of advantage. To me it looks like all C++ does is add an extra layer of obfuscation. I don't expect an explanation here, but if somebody could point me to one I would appreciate it. 50.43.12.61 ( talk) 20:35, 17 March 2014 (UTC)
std::string x = "Hello";
in a scope and use it very much as though it were int x = 123;
. A C++ bignum library will likewise give you bignums that work like built-in integral types; you don't have to worry about refcounting or whatever just as you don't have to worry about that for ints. Generally, unless you're implementing one of these libraries, you rarely need to use dynamic allocation (malloc/free/new/delete) at all in C++, which is good since it's a huge source of bugs in C. --
BenRG (
talk) 05:37, 18 March 2014 (UTC)As an alternative you might try an even bigger jump away from C, and look at Learn You a Haskell for Great Good, an online book about Haskell (programming language). Haskell is not for everyone, but using it for a while will get you some understanding of polymorphic type systems (like C++ generics but "done right") and other topics like functional programming, that you'll then be able to transfer to other languages. C++ improves on C but it's also a pretty bad mess because of its constraints of being a low-level language and supporting legacy C code. If your goal is to broaden your horizons rather than to specifically use C++, I'd start with Haskell, Scheme, Python, Go, etc. rather than C++. 70.36.142.114 ( talk) 22:07, 18 March 2014 (UTC)
I just read this strange word. It is hard to follow all new developments in this crazy world. It is not he end of it. What is shibe? -- -- AboutFace 22 ( talk) 21:25, 17 March 2014 (UTC)
Computing desk | ||
---|---|---|
< March 16 | << Feb | March | Apr >> | March 18 > |
Welcome to the Wikipedia Computing Reference Desk Archives |
---|
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
I have to compute these special functions. They have been a part of my life off and on for many years. I wrote a few C# routines for that. The trouble is I need fairly large indices. When I compute them my only control is graphic representation, observing them visually and making sure that they "behave decently." There is another way too, to use different path in recurrence formulas to compute the same function, thus arriving at the function from a different direction. Sometimes I use the double factorials which might be also error prone in some areas because you end up handling huge numbers. In many cases it is iterations over and over again, driving the indices up and up.
What are standard, mathematically correct ways to estimate computational errors in such situations. Where can I find them?
Thanks, -- AboutFace 22 ( talk) 16:16, 17 March 2014 (UTC)
Thank you. Parts of it I have known for years, some of that is new. I can tell you that I had been complacent with my calculations more or less until I checked this. It is a Casio online calculator for Associated Legendre Polynomials. When you increase index n the functions take a totally bizarre shape. Mine behave much, much better. There is another website which I cannot immediately find which makes an error estimate for their code and it is discouraging. Thanks, --- AboutFace 22 ( talk) 18:57, 17 March 2014 (UTC)
Thank you very much. There is a lot of stuff out there when one starts digging. -- AboutFace 22 ( talk) 21:52, 17 March 2014 (UTC)
I need to cut a passage from a song for class presentation. I have the song in MP3 format; what (free?) tool/program should I use to cut the passage and save it as an MP3? Thanks, Drmies ( talk) 17:27, 17 March 2014 (UTC)
I am an old C programmer. C is not perfect but I can make it do whatever I need done. I've been running into C++ for years. I have made a couple of attempts to understand it, but without much success, meaning I don't instantly see how to structure a new program in C++. There are a few little things that C++ introduced that I like, like the double slash comments and the ability to declare variables within blocks below the procedure level, but these don't really touch on C++'s raison d'etre. I have read some explanations of C++ and they list a bunch of things that C++ does, but I fail to see how any of these features translate into any kind of advantage. To me it looks like all C++ does is add an extra layer of obfuscation. I don't expect an explanation here, but if somebody could point me to one I would appreciate it. 50.43.12.61 ( talk) 20:35, 17 March 2014 (UTC)
std::string x = "Hello";
in a scope and use it very much as though it were int x = 123;
. A C++ bignum library will likewise give you bignums that work like built-in integral types; you don't have to worry about refcounting or whatever just as you don't have to worry about that for ints. Generally, unless you're implementing one of these libraries, you rarely need to use dynamic allocation (malloc/free/new/delete) at all in C++, which is good since it's a huge source of bugs in C. --
BenRG (
talk) 05:37, 18 March 2014 (UTC)As an alternative you might try an even bigger jump away from C, and look at Learn You a Haskell for Great Good, an online book about Haskell (programming language). Haskell is not for everyone, but using it for a while will get you some understanding of polymorphic type systems (like C++ generics but "done right") and other topics like functional programming, that you'll then be able to transfer to other languages. C++ improves on C but it's also a pretty bad mess because of its constraints of being a low-level language and supporting legacy C code. If your goal is to broaden your horizons rather than to specifically use C++, I'd start with Haskell, Scheme, Python, Go, etc. rather than C++. 70.36.142.114 ( talk) 22:07, 18 March 2014 (UTC)
I just read this strange word. It is hard to follow all new developments in this crazy world. It is not he end of it. What is shibe? -- -- AboutFace 22 ( talk) 21:25, 17 March 2014 (UTC)