convert string format

17 Message(s) by 9 Author(s) originally posted in ruby programming

From: Junkone

Date: Saturday, October 27, 2007

Hello
I have a date

<convention, data> A string unique to a time duration of 24
	hours between 2 successive midnights defined by the local time
	zone.  The specific representation of a date will depend on
	which calendar convention is in force; e.g., Gregorian,
	Islamic, Japanese, Chinese, Hebrew etc. as well as local
	ordering conventions such as UK: day/month/year, US:
	month/day/year.

	Inputting and outputting dates on computers is greatly
	complicated by these {localisation} issues which is why they
	tend to operate on dates internally in some unified form such
	as seconds past midnight at the start of the first of January
	1970.

	Many software and hardware representations of dates allow only
	two digits for the year, leading to the {year 2000} problem.

	{Unix manual page}: date(1), ctime(3).

	(1997-07-11)

like 20070801 in a string. how do I change it to
2007/08/01 using regex
thanks

From: Tim Hunter

Date: Saturday, October 27, 2007

wrote in message:

Hello
I have a date like 20070801 in a string. how do I change it to
2007/08/01 using regex
thanks

irb(main):001:0> x = '20070801'
=> "20070801"
irb(main):005:0> d = /(\d{4})(\d{2})(\d{2})/.match x
=> #<MatchData:0x56520c>
irb(main):006:0> d[1..3]
=> ["2007", "08", "01"]
irb(main):007:0> d[1..3].join("/")
=> "2007/08/01"

--
RMagick OS X Installer [http://rubyforge.org/projects/rmagick/]
RMagick Hints & Tips [http://rubyforge.org/forum/forum.php?forum_id=1618]
RMagick Installation FAQ

<convention> (FAQ, or rarely FAQL, FAQ list) A document
	provided for many {Usenet} {newsgroups} (and, more recently,
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	The collection of all FAQ lists is one of the most precious
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	assisted by its frequent exposure to criticism by an
	interested, and occasionally well-informed, audience (the
	readers of the relevant newsgroup).

	The main {FTP archive} for FAQs is on a computer called {RTFM}
	at {MIT}, where they can be accessed either {by group
	(ftp://rtfm.mit.edu/pub/usenet-by-group/comp.answers/)} or {by
	hierarchy (ftp://rtfm.mit.edu/pub/usenet-by-hierarchy/)}.
	There is another archive at {Imperial College
	(ftp://src.doc.ic.ac.uk/usenet/news-info/)}, London, UK and a
	{World-Wide Web} archive in {Ohio
	(http://www.cis.ohio-state.edu/hypertext/faq/usenet/top.html)},
	USA.

	The FAQs are also posted to {Usenet} newsgroups:
	{news:comp.answers}, {news:news.answers} and
	{news:alt.answers}.

	(1997-12-08)

[http://rmagick.rubyforge.org/install-faq.html]

From: Xavier Noria

Date: Saturday, October 27, 2007

wrote in message:

Hello
I have a date like 20070801 in a string. how do I change it to
2007/08/01 using regex

A solution

<jargon> A {marketroid} term for something he wants to sell
	you without bothering you with the often dizzying distinctions
	between {hardware}, {software}, {services}, {applications},
	{file formats}, companies, brand names and {operating
	systems}.

	"{Flash} is a perfect image-streaming solution."  "What is
	it?"  "Um...  about a thousand dollars."

	See also: {technology}.

	(1998-07-07)

with unpack:

irb(main):003:0> "20070801".unpack("a4a2a2").join("/")
=> "2007/08/01"

-- fxn

From: Tom Machinski

Date: Saturday, October 27, 2007

wrote in message:

Hello
I have a date like 20070801 in a string. how do I change it to
2007/08/01 using regex
thanks

irb(main):008:0> '20070801'.sub( /(\d{4})(\d{2})(\d{2})/ ) { [ $1, $2,
$3 ].join( '/' ) }
=> "2007/08/01"

OR:

irb(main):010:0> '20070801'.sub( /(\d{4})(\d{2})(\d{2})/, '\1/\2/\3')
=> "2007/08/01"

-Tom

From: Brian Adkins

Date: Saturday, October 27, 2007

wrote in message:

Hello
I have a date like 20070801 in a string. how do I change it to
2007/08/01 using regex
thanks

Just out of curiosity, why do you want to use regular expressions to
solve this? Do not you just want to insert two '/' characters in the
appropriate place?

"20070801".insert(4,'/').insert(7,'/')

From: Brian Adkins

Date: Saturday, October 27, 2007

wrote in message:

Hi --
wrote in message:
wrote in message:
Hello
I have a date like 20070801 in a string. how do I change it to
2007/08/01 using regex
> A solution with unpack:
> irb(main):003:0> "20070801".unpack("a4a2a2").join("/")
> => "2007/08/01"
And here's one with scanf:
"20070801".scanf("%4s%2s%2s").join('/')
=> "2007/08/01"

Yeah, but scanf is implemented in Ruby

<language>

	1. A {relational language} designed by Jones and M. Sheeran in
	1986 for describing and designing circuits (a {hardware
	description language}).  Ruby programs denote {binary
	relations} and programs are built-up inductively from
	primitive relations using a pre-defined set of {relational
	operators}.  Ruby programs also have a geometric
	interpretation as networks of primitive relations connected by
	wires, which is important when layout is considered in circuit
	design.

	Ruby has been continually developed since 1986, and has been
	used to design many different kinds of circuits, including
	{systolic arrays}, {butterfly networks} and arithmetic
	circuits.

	{(ftp://ftp.cs.chalmers.se/pub/misc/ruby/)}.

	E-mail: <graham@cs.chalmers.se>.

	["Ruby - A Language of Relations and Higher-Order Functions",
	M. Sheeran, Proc 3rd Banff Workshop on Hardware Verification,
	Springer 1990].

	(1994-10-27)

	2. One of five pedagogical languages based on {Markov
	algorithms}, used in Higman's report (below).  The other
	languages are {Brilliant}, {Diamond}, {Nonpareil}, and
	{Pearl}.

	["Nonpareil, a Machine Level Machine Independent Language for
	the Study of Semantics", B. Higman, ULICS Intl Report No ICSI
	170, U London (1968)].

	(1994-10-27)

	3. A fully {object oriented} {interpreted} {scripting
	language} by Yukihiro Matsumoto <matz@netlab.co.jp>.

	Similar in scope to {Perl} and {Python}, Ruby has high-level
	{data types}, automatic {memory management}, {dynamic typing},
	a {module} system, {exceptions}, and a rich standard library.
	Other features are {CLU}-style {iterators} for {loop
	abstraction}, {singleton classes}/{methods} and {lexical
	closures}.

	In Ruby, everything is an {object}, including the basic data
	types.  For example, the number 1 is an instance of {class}
	Fixnum.

	Current version (stable): 1.6.7, as of 2002-03-01.

	{Ruby Home (http://www.ruby-lang.org/)}.

	{Ruby Central (http://www.rubycentral.com/)}.

	["Programming Ruby - The Pragmatic Programmer's Guide", David
	Thomas, Andrew Hunt, Yukihiro Matsumoto pub. Addison Wesley
	2000].

	(2002-06-19)

, so it's 25 times slower (at
least by a crude, quick benchmark) than unpack or insert :(

From: 7stud --

Date: Saturday, October 27, 2007

wrote in message:
wrote in message:

> irb(main):003:0> "20070801".unpack("a4a2a2").join("/")
> => "2007/08/01"

And here's one with scanf:

"20070801".scanf("%4s%2s%2s").join('/')
=> "2007/08/01"
Yeah, but scanf is implemented in Ruby, so it's 25 times slower (at
least by a crude, quick benchmark) than unpack or insert :(

I was going to post that same solution, but after timing it, I almost
gagged when I saw the results.

--
Posted via http://www.ruby-forum.com/.

From: 7stud --

Date: Saturday, October 27, 2007

wrote in message:

Yeah, but scanf is implemented in Ruby, so it's 25 times slower (at
least by a crude, quick benchmark) than unpack or insert :(

This one is super speedy:

str = '20070801'
new_str = sprintf("%4s/%2s/%2s", str, str, str)On my system

1. The {supervisor} program or {operating system} on a
	computer.

	2. The entire computer system, including input/output devices,
	the {supervisor} program or {operating system} and possibly
	other {software}.

	3. Any large program.

	4. Any method or {algorithm}.

	[{Jargon File}]

sprintf() is twice as fast as unpack(), which is twice as
fast as match().--
Posted via http://www.ruby-forum.com/.

From: 7stud --

Date: Saturday, October 27, 2007

wrote in message:
wrote in message:
Hello
I have a date like 20070801 in a string. how do I change it to
2007/08/01 using regex
thanks
Just out of curiosity, why do you want to use regular expressions to
solve this? Do not you just want to insert two '/' characters in the
appropriate place?
"20070801".insert(4,'/').insert(7,'/')

Ack. I forgot to time that one....and we've a winner. Nice.

--
Posted via http://www.ruby-forum.com/.

From: ara.t.howard

Date: Sunday, October 28, 2007

wrote in message:

Hello
I have a date like 20070801 in a string. how do I change it to
2007/08/01 using regex
thanks

using regexen for that's suicide unless you want to accept

<library, networking> {Berkeley} {Unix} networking {socket}
	library routine to satisfy a connection request from a remote
	{host}.  A specified socket on the local host (which must be
	capable of accepting the connection) is connected to the
	requesting socket on the remote host.  The remote socket's
	socket address is returned.

	{Unix manual pages}: accept(2), connect(2).

	(1994-11-08)

invalid
time strings. use the functionality

<programming> Waffle for "{features}" or "function".  The
	capabilities or behaviours of a program, part of a program, or
	system, seen as the sum of its {features}.  Roughly, "the
	things it can do".  Generally used in a comparative sense,
	e.g. "The latest update adds some useful functionality".

	(1997-07-14)

already provided by ruby:

cfp:~ > cat a.rb
require 'time'

puts Time.parse('20070801').strftime('%Y/%m/%d')

puts Time.parse('20070842').strftime('%Y/%m/%d') rescue puts $!.messagecfp:~ > ruby a.rb
2007/08/01
argument out of rangekind regards.a @xxxxxxxxxxx http://codeforpeople.com/
--
share your knowledge. it's a way to achieve immortality.
h.h. the 14th dalai lama

From: Brian Adkins

Date: Sunday, October 28, 2007

wrote in message:
wrote in message:
> Yeah, but scanf is implemented in Ruby, so it's 25 times slower (at
> least by a crude, quick benchmark) than unpack or insert :(
This one is super speedy:
str = '20070801'
new_str = sprintf("%4s/%2s/%2s", str, str, str)
On my system sprintf() is twice as fast as unpack(), which is twice as
fast as match().

Yes, but fast and incorrect is a bad combination. :)

From: Brian Adkins

Date: Sunday, October 28, 2007

wrote in message:
wrote in message:
> Hello
> I have a date like 20070801 in a string. how do I change it to
> 2007/08/01 using regex
> thanks
using regexen for that's suicide unless you want to accept invalid
time strings.

Good point, but with a format like "20070801", there's a good chance
this isn't user input, but serialized data

<data, data processing, jargon> /day't*/ (Or "raw data")
	Numbers, {characters}, {images}, or other method of recording,
	in a form which can be assessed by a human or (especially)
	input into a {computer}, stored and {processed} there, or
	transmitted on some {digital channel}.  Computers nearly
	always represent data in {binary}.

	Data on its own has no meaning, only when interpreted by some
	kind of {data processing system} does it take on meaning and
	become {information}.

	People or computers can find patterns in data to perceive
	information, and information can be used to enhance
	{knowledge}.  Since knowledge is prerequisite to wisdom, we
	always want more data and information.  But, as modern
	societies verge on {information overload}, we especially need
	better ways to find patterns.

	1234567.89 is data.

	"Your bank balance has jumped 8087% to $1234567.89" is
	information.

	"Nobody owes me that much money" is knowledge.

	"I'd better talk to the bank before I spend it, because of
	what has happened to other people" is wisdom.

	(1999-04-30)

that's already been parsed/
validated and just needs to be formatted.

From: ara.t.howard

Date: Sunday, October 28, 2007

wrote in message:

Yes, but fast and incorrect is a bad combination. :)

hey! it worked for fortran! ;-)

a @xxxxxxxxxxx http://codeforpeople.com/
--
share your knowledge. it's a way to achieve immortality.
h.h. the 14th dalai lama

From: ara.t.howard

Date: Sunday, October 28, 2007

wrote in message:

Good point, but with a format like "20070801", there's a good chance
this isn't user input, but serialized data that's already been
parsed/
validated and just needs to be formatted.

could be. still, c programs aren'torious for using crappy methods
of string/date generation

An attempt to classify the degree of sophistication of
	programming languages.

	See {First generation language} -- {Fifth generation
	language}.

	(1995-06-15)

and dumping out bad dates - we had one
system that crashed for years every newyear's eve for years until I
got around to hacking a wrapper

<programming> Code which is combined with another piece of
	{code} to determine how that code is executed.  The wrapper
	acts as an interface between its caller and the wrapped code.
	This may be done for compatibility, e.g. if the wrapped code
	is in a different programming language or uses different
	calling conventions, or for security, e.g. to prevent the
	calling program from executing certain functions.  The
	implication is that the wrapped code can only be accessed via
	the wrapper.

	(1998-12-15)

on it... give you one guess why ;-)

a @xxxxxxxxxxx http://codeforpeople.com/
--
it isn't enough to be compassionate. you must act.
h.h. the 14th dalai lama

From: M. Edward

Date: Sunday, October 28, 2007

wrote in message:
wrote in message:
Good point, but with a format like "20070801", there's a good chance
this isn't user input, but serialized data that's already been parsed/
validated and just needs to be formatted.
could be. still, c programs aren'torious for using crappy methods of
string/date generation and dumping out bad dates - we had one system
that crashed for years every newyear's eve for years until I got around
to hacking a wrapper on it... give you one guess why ;-)
a @xxxxxxxxxxx http://codeforpeople.com/
--
it isn't enough to be compassionate. you must act.
h.h. the 14th dalai lama

You had to work on New Years' Eve? Bummer ...

From: 7stud --

Date: Sunday, October 28, 2007

wrote in message:
wrote in message:
On my system sprintf() is twice as fast as unpack(), which is twice as
fast as match().
Yes, but fast and incorrect is a bad combination. :)

No wonder it was so much faster than this one:

str = '20070801'
new_str = sprintf("%s/%s/%s", str[0..3], str[4..5], str[6..7]):(
:(
:(
--
Posted via http://www.ruby-forum.com/.

From: Stefan Rusterholz

Date: Sunday, October 28, 2007

wrote in message:
wrote in message:
wrote in message:
On my system sprintf() is twice as fast as unpack(), which is twice as
fast as match().

Yes, but fast and incorrect is a bad combination. :)
No wonder it was so much faster than this one:
str = '20070801'
new_str = sprintf("%s/%s/%s", str[0..3], str[4..5], str[6..7])
:(
:(
:(

Well, use sprintf("%s/%s/%s", str[0,4], str[4,2], str[6,2]) then, it's
still a lot faster than the other solutions.

Regards
Stefan
--
Posted via http://www.ruby-forum.com/.

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