Regular Expressions for Information Processing in ABAP

32 Pages·2006·0.58 MB·English

Regular Expressions for
Information Processing
in ABAP
Ralph Benzinger
SAP AG
Regular Expression Primer
Using Regular Expressions in ABAP
Working with Regular Expressions
Ubiquitous Text Processing (1)
Checking input for validity:
Does credit card number contain only digits, hyphens, and spaces?
METHODS check
IMPORTING cardno TYPE c
RETURNING result TYPE abap_bool.
"…
1234 5678 1234 5678
1234 5678 1234 XXXX
1234-5678-1234-5678
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Ubiquitous Text Processing (2)
Extracting information from text:
What is the document ID requested by the web client?
METHODS retrieve
IMPORTING url TYPE c
RETURNING doc TYPE xstring.
"…
http://sap.com/&user=ralph&id=1234&lang=EN
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Ubiquitous Text Processing (3)
Normalizing values:
Eliminate non-digits in phone number for data export
METHODS export
IMPORTING phoneno TYPE c
RETURNING digits TYPE n.
"…
[phone]
496227747474
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Sample Text Processing Problem
Remove all HTML tags from a given block of text
<h2 id="slogan">Leading the Web to Its Full
Potential...</h2>
<p class="small">The World Wide Web Consortium
(<acronym>W3C</acronym>) develops interoperable < >
technologies to lead the Web to its full potential.
W3C is a forum for information, commerce,
Leading the Web to Its Full Potential... The
communication, and collective understanding. On this
page, you'll find <a href="#news">W3C news</a>,
World Wide Web Consortium (W3C) develops interoperable
links to <a href="#technologies">W3C
technologies to lead the Web to its full potential. W3C is a
technologies</a> and ways to <a href="#contents">get
involved</a>. New visitors can find help in <cite><a
forum for information, commerce, communication, and
href="/2002/03/new-to-w3c">Finding Your Way at
collective understanding. On this page, you'll find W3C
W3C</a></cite>. We encourage you to read the
<cite><a href="/Consortium/Prospectus/">Prospectus
news, links to W3C technologies and ways to get involved.
</a></cite> and learn <a href="/Consortium/">more
New visitors can find help in Finding Your Way at W3C.
about W3C</a>.</p>'
We encourage you to read the Prospectus and learn more
about W3C.
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“Patterns? Been there, done that!”
Traditional ABAP offers some trivial patterns for text processing
* one or more characters
+ any single character
(cid:132) For use with CP operator
(cid:132) Also used by F4 help
Sorry, but CP less useful than it seems
(cid:132) Cx abbreviates “contains x”, but ...
(cid:132) CP abbreviates “covers pattern” – does not search inside of text
WHILE text CP '<*>'.
" loop hardly ever entered
ENDWHILE.
(cid:132) Pattern “ *<*>* ” won't tell us position of closing bracket
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Improving Information Processing with REs
Regular Expressions (REs, regexes)
provide powerful pattern language for text processing
(cid:132) Well understood
Developed by mathematician Kleene in the 1950s
(cid:139)
(cid:132) Powerful
Highly focused special purpose language
(cid:139)
Many common text processing tasks turn into
(cid:139)
simple one-liners
(cid:132) Standardized and widely used
Made popular by Unix tools: grep, sed, awk, emacs
(cid:139)
Stephen C. Kleene
Built into some languages like Perl and Java;
(cid:139)
Image ©U. of Wisconsin
add-on libraries available for many others
Early Unix de-facto standard formalized in PCRE and POSIX
(cid:139)
As of Release 7.00, ABAP supports POSIX-style regular expressions
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Regular Expression Basics
Regular expressions are patterns built from
(cid:132) Literals (characters)
(cid:132) Operators (meta characters)
. * + ? | ^ $ ( ) [ ] { } \
(cid:132) Prepending " \ " turns operators into literals
Basic regex terminology
(cid:132) An RE represents a set of literal text strings
(cid:132) RE matches text if complete text is represented by RE Covers
(cid:132) REs are commonly used for searching text
(cid:132) Text to be searched may contain one or more matches Contains
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Tool Support: Regex Toy
DEMO_REGEX_TOY
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