[FM Discuss] command line manual - please have a squiz

[Andy Oram]

Well, we should get rid of fuzzy, even though I think it gives the chapter a warm fuzzy feel. I'm always balancing casualness against precision, and I don't want to press for something that people with a strong background in the field will find undisciplined.

But introducing the concepts of regular expressions to new users is a delicate matter that can't be pushed too fast. I'm glad you provided examples, but I think we need to still slow things down.

Andy

----- Original Message -----
From: "Edward Cherlin" <echerlin at gmail.com>
To: discuss at lists.flossmanuals.net
Sent: Thursday, April 9, 2009 6:01:48 PM GMT -05:00 US/Canada Eastern
Subject: Re: [FM Discuss] command line manual - please have a squiz

On Thu, Apr 9, 2009 at 8:20 AM, Andy Oram <andyo at oreilly.com> wrote:
> I look forward to the improvements listed below. But don't throw out the word "fuzzy" entirely. I want terms that mean something to average readers. They won't immediately understand what you mean by "pattern" (it has innumerable meanings in everyday life and compute science). The reader for this book, if I have the right image of the reader, won't connect "fuzzy" with the academic use by search technologists. But its use in the chapter could be reduced.

I always try to avoid using ambiguous words and phrases, or else to
give a reasonably precise statement of what *I* intend the word to
mean in the context given. What did *you* intend it to mean it grep?
You begin

Regular Expressions

Text processing often involves fuzzy matching.

You go on to discuss

o fuzzy quantities. "Any number" or "3 to 5"

o Fuzzy Matches, Classes, and Ranges "The dot is commonly combined
with one of the fuzzy quantifiers in the previous section."

This use of fuzzy matching is correct, but does not capture the whole
idea of regexes and pattern matching. What we are trying to get at is
precise definition of sets of alternatives, including ranges. How
about something like this?
=====
Text processing often involves searches for any of a range of
alternatives, or combining searches for parts of a word or phrase. You
don't want to search for "help", and then "helper", and then "helping"
and so on as separate commands. Using '.', which matches any
character, and '*', which matches zero or more of the previous item,
the pattern

help.*

does this in one search, also finding "helps", "helped", and so on.

You do want to be able to find names of very general types. Suppose
you want to find names consisting of a letter followed by any number
of letters and numbers. That would be

[a-zA-Z][a-zA-Z0-9]*

Maybe you need to find all text files in a directory, regardless of
their names. That is

.*.txt

Maybe you want to find words of three to five letters, or other such
fuzzy criteria. You can use curly brackets '{}' to specify a numeric
range.

.{3,5}

Sometimes you might want to match just a few specific words. You can
use '|' for this.

apple|pear|cherry

Regular expressions (regexes) give you a precise language for
specifying exactly how much fuzz to apply to any part of a search.
This chapter explains the use of regexes in grep and sed. Use in other
programs, including file globbing in a shell, is similar, but differs
significantly in details.
=====
(Fuzz is a term of art in numerical analysis, with a meaning
consistent with this.)

> Andy
>
> ----- Original Message -----
> From: "adam hyde" <adam at flossmanuals.net>
> To: discuss at lists.flossmanuals.net
> Sent: Thursday, April 9, 2009 10:59:30 AM GMT -05:00 US/Canada Eastern
> Subject: Re: [FM Discuss] command line manual - please have a squiz
>
> On Thu, 2009-04-09 at 16:48 +0200, Luka Frelih wrote:
>> heya!
>>
>> great book, nice catch fixing the pre bold font.
>>
>> on page 77 (advanced  part toc) gnu screen lost the space between words
>>
>> in regexp chapter, "fuzzy matching" is used where i guess "pattern
>> matching" is more appropriate.
>> i understand fuzzy to mean approximate matching, using soundex or
>> levenshtein distances to find similar strings, like in typo correction
>> or spellchecking.
>>
>> perhaps it would be nice to mention the rpl command in the sed chapter?
>> i know it's not installed by default but it's a more user friendly way
>> to perform basic search and replace, which is usually the first reason
>> to use sed in a command line
>>
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