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The most surprising Unix programs

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Re: The most surprising Unix programs

#91

Post by bloomer »

londons_explore wrote: post #53

> The math library for Bob Morris's variable-precision desk calculator used backward error analysis to determine the precision necessary at each step to attain the user-specified precision of the result. I wonder if compilers could do this today? If you can bound values for floating point operations, you might be able to replace them with fixed point equivalents and get a big speedup. You might also be able to replac…

This isn’t a performance optimization but rather an accuracy optimization. Even if the requested output is a double (64-bits) the intermediate calculations often need to be done to higher precision to get fully accurate answers. Note that the desktop calculator on Android does the same analysis by using computable numbers.

https://dl.acm.org/doi/10.1145/2911981

Is a nice overview.

Re: The most surprising Unix programs

#92

Post by elteto »

kmstout wrote: post #82

sl ``` ( ) (@@) ( ) (@) () @@ O @ O @ O (@@@) ( ) (@@@@) ( ) ==== ________ ___________ _D _| |_______/ \__I_I_____===__|_________| |(_)--- | H\________/ | | =|___ ___| _________________ / | | H | | | | ||_| |_|| _| \_____A | | | H |__--------------------| [___] | =| | | ________|___H__/__|_____/[][]~\_______| | -| | |/ | |-----------I_____I [][] [] D |=======|____|________________________|_ __/ =| o |=-O=====O=====O=…

During college my friend and I kept an innocent prank going for a couple of years: every time one of us left our laptops unlocked the other would jump in and type 'alias ls=sl' in the prompt and then clear the screen. Good times.

Re: The most surprising Unix programs

#93

Post by bloomer »

ur-whale wrote: post #9

The fact that dc does (or at least tries to) guarantee error bounds on the result is news to me. And if that does indeed work, that's pretty cool.

The default Android calculator app by Hans Boehm (developer of the Boehm Garbage Collector as well) does this by using the computable real numbers.

https://dl.acm.org/doi/10.1145/2911981

Provides a good overview of how it works and perms website has more information.

What’s cool about the computable reals implementation is you can increase the precision after the fact and it will recalculate up to that precision. Basically it memoizes the steps of the calculation and how they affect the precision.

Re: The most surprising Unix programs

#94

Post by jimhefferon »

nicoburns wrote: post #38
thaumasiotes wrote: post #15

Earlier quoted context omitted.

> On the surface it sounds a lot like it would produce error messages like “expected ‘;’” that most beginner programmers come to hate Do people really come to hate these? I'd expect the opposite -- that people would start off hating messages like "expected ';'", but fairly quickly become accustomed to what they almost always mean. As long as you can look at the message and have a good idea of what's wrong, it's not a…

Once you've used a compiler like Rust or Elm that actually provides suggestions for common solutions to these errors (effectively building the tribal knowledge of what the error "really means" into the compiler itself), it's hard to tolerate these cryptic errors that only really make sense to machines.

I'd like to know more about how they do this. Do you know a good source?

Re: The most surprising Unix programs

#97

Post by bloopernova »

abetusk wrote: post #71

For me, the most surprising one was paste. paste allowed me to interleave to streams or to split out a single stream into two columns. I'd been writing custom scripting monstrosities before I discovered paste: $ paste I wonder what other unix gems I've been missing...

Paste is quite wonderful. It adds a lot of flexibility in output and should definitely be more widely known.

Re: The most surprising Unix programs

#98

Post by jldugger »

jawilson wrote: post #85

I've written a few useful scripts that everyone should have. histogram - simply counts each occurrence of a line and then outputs from highest to lowest. I've implemented this program in several different languages for learning purposes. There are practical tricks that one can apply, such as hashing any line longer than the hash itself. unique - like uniq but doesn't need to have sorted input! again, one can simply h…

> histogram

Is this much different than `alias histogram="sort $1 | uniq -c | uniq -nr"`

Sidenote: I started https://github.com/jldugger/moarutils as a means of publishing and sharing these, but it turns out I don't even have a lot of dumb ideas. Will probably end up bookmarking this HN post for "later."

Re: The most surprising Unix programs

#99

Post by loeg »

abetusk wrote: post #71

For me, the most surprising one was paste. paste allowed me to interleave to streams or to split out a single stream into two columns. I'd been writing custom scripting monstrosities before I discovered paste: $ paste I wonder what other unix gems I've been missing...

The related join(1) and comm(1) are oft-missed and occasionally helpful.

Re: The most surprising Unix programs

#100

Post by loeg »

ahoka wrote: post #62
mci wrote: post #26

> Hidden inside WWB (writer's workbench), Lorinda Cherry's Parts annotated English text with parts of speech, based on only a smidgen of English vocabulary, orthography, and grammar. Writer's Workbench was indeed a marvel of 1970's limited-space engineering. You can see it for yourself [1]: the generic part-of-speech rules are in end.l, the exceptions in edict.c and ydict.c, and the part-of-speech disambiguator in ps…

It's very interesting that the readme calls shell scripts "runcom", an archaic name coming from the Compatible Time Sharing System. This is also the origin for rc files.

"Runcom" is still referenced by that name in BSD init(8):

https://svnweb.freebsd.org/base/head/sbin/init/init.c?view=m...

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