Split a string by a Regular Expression
Posted: Thu Aug 31, 2017 11:33 pm
Hi,
there are already some procedures here on the forum for splitting strings, but I'm not aware of a general purpose procedure that splits a string by a Regular Expression.
Though PureBasic has the built-in function ExtractRegularExpression(), this will only retrieve the parts of the source string which match the Regular Expression, while the parts of the source string which don't match won't be retrieved. Sometimes this is exactly what is needed.
However, often we want to get all parts of the source string as the result. The following function splits a string into parts, that match or don't match the given Regular Expression. In other words, the generated list of parts contains the whole string.
there are already some procedures here on the forum for splitting strings, but I'm not aware of a general purpose procedure that splits a string by a Regular Expression.
Though PureBasic has the built-in function ExtractRegularExpression(), this will only retrieve the parts of the source string which match the Regular Expression, while the parts of the source string which don't match won't be retrieved. Sometimes this is exactly what is needed.
However, often we want to get all parts of the source string as the result. The following function splits a string into parts, that match or don't match the given Regular Expression. In other words, the generated list of parts contains the whole string.
Code: Select all
; -- Split a string by a Regular Expression
; tested with PB 5.60
; by Little John, <http://www.purebasic.fr/english/viewtopic.php?f=12&t=69071>
CompilerIf #PB_Compiler_IsMainFile
EnableExplicit
CompilerEndIf
Structure SplitString
content$
match.i
EndStructure
Procedure.i SplitByRegEx (regEx.i, source$, List part.SplitString())
; -- split a string into parts, that match or don't match a Regular Expression
; in : regEx : number of a Regular Expression generated by CreateRegularExpression()
; source$: string to be split into parts
; out: part() : resulting list of parts
; return value: number of elements in part():
; 0 if source$ = "", > 0 otherwise;
; -1 on error
Protected.i left, right
If ExamineRegularExpression(regEx, source$) = 0
ProcedureReturn -1 ; error
EndIf
ClearList(part())
left = 1
While NextRegularExpressionMatch(regEx)
right = RegularExpressionMatchPosition(regEx)
If left < right
AddElement(part())
part()\content$ = Mid(source$, left, right-left)
part()\match = #False
EndIf
AddElement(part())
part()\content$ = RegularExpressionMatchString(regEx)
part()\match = #True
left = right + RegularExpressionMatchLength(regEx)
Wend
If left <= Len(source$)
AddElement(part())
part()\content$ = Mid(source$, left)
part()\match = #False
EndIf
ProcedureReturn ListSize(part()) ; success
EndProcedure
CompilerIf #PB_Compiler_IsMainFile
; -- Demo
Procedure SplitDemo (rex.i, source$)
Protected n.i
Protected NewList part.SplitString()
n = SplitByRegEx(rex, source$, part())
If n = -1
Debug "Error with ExamineRegularExpression()"
End
EndIf
Debug "'" + source$ + "' split into " + n + " part(s):"
ForEach part()
If part()\match = #False
Debug " [-] " + part()\content$
Else
Debug " [+] " + part()\content$
EndIf
Next
Debug ""
EndProcedure
Define regEx$, rex.i, source$
regEx$ = "<[^>]*>"
rex = CreateRegularExpression(#PB_Any, regEx$)
If rex = 0
Debug "Error: " + RegularExpressionError()
End
EndIf
source$ = "I like <b>bold</b> and <i>italic</i> fonts."
SplitDemo(rex, source$)
source$ = "<b></b> and <i></i>"
SplitDemo(rex, source$)
source$ = "plain text"
SplitDemo(rex, source$)
CompilerEndIf
