Regular Expression or Regex

[hmgchang]

Hello Masters,
I was looked into the check.hb files and came across these lines,

FOR EACH match IN hb_regexAll( "([A-Za-z] |[^A-Za-z_:]|^)([A-Za-z_][A-Za-z0-9_]+\()", cFileStripped,,,,, .F. )
IF Len( match[ 2 ][ _MATCH_cStr ] ) != 2 .OR. !( Left( match[ 2 ][ _MATCH_cStr ], 1 ) $ "D" /* "METHOD" */ )
cProper := ProperCase( hAll, hb_StrShrink( match[ 3 ][ _MATCH_cStr ] ) ) + "("
IF !( cProper == match[ 3 ][ _MATCH_cStr ] ) .AND. ;
!( Upper( cProper ) == Upper( "FILE(" ) ) .AND. ; /* interacts with "file(s)" text */
!( Upper( cProper ) == Upper( "TOKEN(" ) ) .AND. ; /* interacts with "token(s)" text */
!( Upper( cProper ) == Upper( "INT(" ) ) .AND. ; /* interacts with SQL statements */
( ! lInCommentOnly .OR. !( "|" + Lower( cProper ) + "|" $ Lower( "|Max(|Min(|FOpen(|Abs(|Log10(|GetEnv(|Sqrt(|Rand(|IsDigit(|IsAlpha(|" ) ) )
cFile := Left( cFile, match[ 3 ][ _MATCH_nStart ] - 1 ) + cProper + SubStr( cFile, match[ 3 ][ _MATCH_nEnd ] + 1 )
IF lVerbose
OutStd( cFileName, match[ 3 ][ _MATCH_cStr ], cProper, "|" + match[ 1 ][ _MATCH_cStr ] + "|" + hb_eol() )
ENDIF
nChanged++
ENDIF
ENDIF
NEXT

I tried to figure out how the Regex works, but not easy. Can you pls give me some very basic understanding of Regular Expression and the usage ?
Thank you in advance !

[esgici]

Hi Chang

I tried to figure out how the Regex works, but not easy. Can you pls give me some very basic understanding of Regular Expression and the usage ?

You may find some basic info about regular expression here.

For Harbour specific subject asking to Harbour Users Group or following Harbour Developers Group may be more useful.

Happy HMG'ing

[Amarante]

Below an example of the use of Regular Expression:

Code: Select all

*****************************************************************************
FUNCTION Swap_RegExp( cString, cExpRegular, cSwap )
* Parameters:
* cString      <expC> - string with data
* cExpRegular  <expC> - string with regular expression to find
* cSwap        [expC] - string to change (default SPACE( 1 ) )
* Return:
* expC - cString changed
*****************************************************************************
LOCAL	aFound
IF cSwap = NIL
  cSwap := SPACE( 1 )
ENDIF
cExpRegular := HB_RegexComp( cExpRegular )
DO WHILE .NOT. EMPTY( aFound := HB_Regex( cExpRegular, cString ) )
  cString := aFound[ 2 ] + cSwap + aFound[ LEN( aFound ) ]
ENDDO
RETURN cString

[danielmaximiliano]

Gracias por compartir Amarante

[esgici]

Hi Amarate

Below an example of the use of Regular Expression:

Thank to share, but;

Is this a "working" sample ?

fe

Code: Select all

LOCAL   aFound
...
  cString := aFound[ 2 ] ...    <- without declared aFound is an array

is this legal ?

And, we need a sample statement to call / apply this function for understanding the subject,

by see a regular expression is similar to what ?

Happy HMG

[Amarante]

esgici,
You were correct. Inadvertently I copied a routine part of my use and had not verified their operation. Follows, for those interested, the routine corrected and examples of using regular expressions.
hugs

Code: Select all

PROCEDURE MAIN()
LOCAL xRegex
LOCAL aMatch
LOCAL cStr := "This Text +Plus Date [1962-11-20] is A.3265-5"


// Example of using regular expression:
*------------------------------------------------------------
* checks if a text contains YYYY-MM-DD 
*------------------------------------------------------------
xRegex := HB_RegexComp( "([0-9]{4}[-][0-9]{2}[-][0-9]{2})" )
aMatch := HB_Regex( xRegex, cStr )
*------------------------------------------------------------
* Found
*------------------------------------------------------------
IF .NOT. EMPTY( aMatch )
  MsgInfo( aMatch[ 1 ] )
ENDIF


// Example of using Swap_RegExp function:
*------------------------------------------------------------
* regular expression (*)
*------------------------------------------------------------
cStr := Swap_RegExp( cStr, "([0-9]{4}[-][0-9]{2}[-][0-9]{2})", "Secret" )
MsgInfo( cStr )


*****************************************************************************
FUNCTION Swap_RegExp( cString, cExpRegular, cSwap )
* Parameters:
* cString      <expC> - string with data
* cExpRegular  <expC> - string with regular expression to find
* cSwap        [expC] - string to change (default SPACE( 1 ) )
* Return:
* expC - cString changed
*****************************************************************************
LOCAL   aFound
IF cSwap = NIL
  cSwap := SPACE( 1 )
ENDIF
cExpRegular := HB_RegexComp( cExpRegular )
IF .NOT. EMPTY( aFound := HB_Regex( cExpRegular, cString ) )
  cString := STRTRAN( cString, aFound[ 2 ], cSwap )
ENDIF
RETURN cString

[Javier Tovar]

No entiendo bien esto de expresiones reguleres, a que se refieren?.

Veo en los ejemplos que hay "Say", esto es en modo consola solamente?

Saludos

///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

I do not understand this in reguleres expressions that refer to?.

I see in the examples that there is "Say" that is only in console mode?

regards

[Amarante]

No entiendo bien esto de expresiones reguleres, a que se refieren?.

Veo en los ejemplos que hay "Say", esto es en modo consola solamente?

Saludos

///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

I do not understand this in reguleres expressions that refer to?.

I see in the examples that there is "Say" that is only in console mode?

regards

Javier,
Examples are pure Harbour, so the use of SAY to display the result.
A regular expression in Computing, sets a standard to be used to find or replace words or groups of words. It is an accurate way to make certain portions of the search text.

For example, if the set of words is {wing, car, garden, eggs, ground} and regular expression search for a pattern rr, get the words car and land.
There are different formats to set up regular expressions, but with some general notions is possible to understand much of the expressions. Source: Wikipedia - Regular Expression

Read more at the Net Workshop: http://www.oficinadanet.com.br/artigo/p ... -regulares" onclick="window.open(this.href);return false;

Hope this helps.
hugs
----
Javier,
Los ejemplos están em Harbour, por lo que el uso de SAY es para mostrar el resultado.
Una expresión regular en Informática, establece un estándar que se utiliza para buscar o reemplazar palabras o grupos de palabras. Es una forma precisa para que ciertas partes del texto de búsqueda.

Por ejemplo, si el conjunto de palabras es {ala, coche, jardín, huevos, tierra} y búsqueda de expresiones regulares para un rr patrón, consiga la palabra coche y la tierra.
Existen diferentes formatos para crear expresiones regulares, pero con algunas nociones generales es posible entender gran parte de las expresiones. Fuente: Wikipedia - Expresión Regular

Ver más en el Taller neto: http://www.oficinadanet.com.br/artigo/p ... -regulares" onclick="window.open(this.href);return false;

Espero que esto ayude.
Abrazos

[Javier Tovar]

Muchas gracias por la información.

Saludos
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

Thank you very much for the information.

regards

[serge_girard]

Hi All,

Regex can also be used in testing emailadresses:

Code: Select all

* checks if a text is a valid emailadres
cStr1 := "sg@host.com"	// VALID
cStr2 := "sg#host.com"	// INVALID

IF Is_Valid_Emailaddress(cStr1)   
	MsgInfo( cStr1  + ' is a VALID emailadres ', 'OK'  )
ELSE
   MsgInfo( cStr1  + ' is an invalid emailadres !!', 'NOK' )
ENDIF


IF Is_Valid_Emailaddress(cStr2)   
	MsgInfo( cStr2  + ' is a VALID emailadres ', 'OK'  )
ELSE
   MsgInfo( cStr2  + ' is an invalid emailadres !!', 'NOK' )
ENDIF

Function Is_Valid_Emailaddress(cStr)
/**********************************/
xRegex := HB_RegexComp( "([_\.0-9a-zA-Z-]+@([0-9a-zA-Z][0-9a-zA-Z-]+\.)+[a-zA-Z]{2,6})" )
aMatch := HB_Regex( xRegex, cStr  )
IF .NOT. EMPTY( aMatch )
   RETURN .T. // valid emailadres
ELSE
   RETURN .F. // invalid emailadres
ENDIF

It has not been tested extensively so I'm not sure if it is 100% OK.

Greetings,

Serge