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From: roby <roby.nowak@gmail.com>
Newsgroups: comp.soft-sys.math.mathematica
Subject: Re: Chained-functional notation examples?
Date: Fri, 9 May 2014 06:06:05 +0000 (UTC)
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Am Dienstag, 6. Mai 2014 08:26:46 UTC+2 schrieb Unknown:
> I came to 'Mathematica' via Xahlee's criticism of the ad-hoc nature of
>
> unix-piping [functional notation].  He claims [& I believe him] that Mathematica has a better, more consistent notation.  But the facility of PRE, IN & POST-fix alternatives, seems bad.  You want ONE way of acieving the goal. More rules just increases mental load.
>
>
>
> A major benefit of functional [unix-piping] programming style, is that you
>
> don't need to remember the-full-journey: you just need to remember the previous stage's output. Nor do you need to remember several names: the previous output is just "it".  A superficial read through a recent article[s] here, about <collecting data from several servers, and agregating it, and sending the result to a master> seemed very interesting, and matches my ideas of using functional programming.  But I can't afford to invest in ANOTHER notation/syntax, without good prospect of productivety increase.
>
>
>
> Just as a test, how would Mathematica handle the following [or part of]
>
> little task:
>
>
>
> search all files in Dir=tree D |
>
>  which are less than N days-old |
>
>  and which contain string S1 |
>
>  and which contain string S2 .
>
>
>
> Actually, this seems not a good example, since it's biased towards the *nix
>
> file system's format/syntax.
>
>
>
> Try:
>
> Search in table of ListOfOpenFiles for lineS with path-P [field] |
>
>  which have same tty-field as line with path-P2 & program-M [field]
>
>
>
> This sounds like a data-base problem?
>
>
>
> Or is there a nice list of 'such' Mathematica examples?
>
>
>
>  Thanks,
>
>
>
> == John Grant.


Well, I think that postfixing by use of the Mathematica Postfix operator "//"
accompanied by use of Mathematica pure Function "&" with access to the last result =
by using Mathematica Slot "#" (argument to the pure Function)
mimics *nix piping best:

the following gets all files of "c:/temp" in all sub dirs
older than 200 days
containing at least one of the strings "str1", "str2" :


"c:/temp" //
FileNames["*", #, Infinity]& //
Select[#, DateDifference[FileDate[#], DateList[]] > 200 &]& //
Select[#, StringMatchQ[#, "*str1*"] || StringMatchQ[#, "*str2*"]&] &

Regards Robert