10-03-2022, 12:28 AM
(This post was last modified: 10-03-2022, 03:20 PM by TerryRitchie.)
UPDATE: I made changes to the code with great suggestions and code examples from Pete. The routine is much more stable now. Thanks Pete!
By the way - writing text parsing routines is much harder than it looks. So much to consider in their design.
While writing the library for lesson 20 of the tutorial I wrote a text parser that's fairly efficient. I needed a parsing routine that reported the number of lines the input text string would be parsed to and could deliver one line of text at a time on demand. This is what I came up with:
Drop the function into your own code and parse away.
By the way - writing text parsing routines is much harder than it looks. So much to consider in their design.
While writing the library for lesson 20 of the tutorial I wrote a text parser that's fairly efficient. I needed a parsing routine that reported the number of lines the input text string would be parsed to and could deliver one line of text at a time on demand. This is what I came up with:
Code: (Select All)
FUNCTION ParseText$ (TextIn AS STRING, MaxWidth AS INTEGER, Action AS INTEGER) STATIC
'-> Modifications added suggested by Pete 10/03/22. Corrects issue of crashing and mishandling of text
' in certain situations. (additions remarked in code below)
' - Function exit if text sent in is null
' - Handles non-breaking strings larger than space allocated
' - Handles end of text that has no trailing space
' - Clear text for next parsing event
'-> Parses the string passed in into multiple lines of the maximum width desired
' The first time the function is called, regardless of action, the TextIn string is fully parsed
' Subsequent calls to the function with the same text will not parse the TextIn string again
'-> INPUT PARAMETERS:
' TextIn - the text string sent into the function
' MaxWidth - maximum width of text on a line
' Action - 1 reports number of lines created, 0 returns lines of parsed text ("" = finished)
'-> EXAMPLE:
' t$ = "The rain in Spain falls mainly on the plain. The weather in Spain seems pretty good!"
' Lines = VAL(ParseText$(t$, 40, 1)) ' report number of lines the text was parsed into
' DO ' get all parsed lines of text
' TextLine$ = ParseText$(t$, 40, 0) ' return the next line of parsed text
' IF TextLine$ <> "" THEN PRINT TextLine$ ' could easily be saved to an array as well
' LOOP UNTIL TextLine$ = "" ' ParseText$ returns null when all lines returned
'-> There is no need to have ParseText$ report the number of lines needed. A simple counter could be
' placed within the DO...LOOP as well. The report for the number of lines the text was parsed into will
' be returned as a string and need converted to a value VAL() as seen in the 2nd line of the example.
DIM PText AS STRING ' previous text that was sent in
DIM Index AS INTEGER ' array index counter
DIM Plen AS INTEGER ' parse string length
DIM Char AS STRING * 1 ' character analyzer
DIM Parse AS STRING ' parsed string
DIM WText AS STRING ' working text string
DIM Done AS INTEGER ' flag to indicate parsing finished
IF MaxWidth <= 0 THEN ParseText$ = "": EXIT FUNCTION ' (Pete) leave if null text sent in
IF PText <> TextIn THEN ' was a new text string sent in?
PText = TextIn ' yes, remember text that was sent in
WText = TextIn ' get text sent in to work with
Index = 0 ' reset index counter
Done = 0 ' reset finished flag
REDIM Text(0) AS STRING ' reset text array
END IF
IF NOT Done THEN ' has parsing already been performed?
DO ' no, begin array loop
Index = Index + 1 ' increment index counter
REDIM _PRESERVE Text(Index) AS STRING ' increase size of array
' (Pete) Non-breaking string larger than space alloted checked below.
IF LEN(WText) > MaxWidth AND INSTR(MID$(WText, 1, MaxWidth + 1), " ") = 0 THEN ' (Pete)
Plen = MaxWidth ' (Pete) set length to maximum size
Parse = MID$(WText, 1, Plen) ' (Pete) get the maximum size string allowed
ELSE
IF MID$(WText, MaxWidth + 1, 1) <> " " THEN ' (Pete) text with no trailing space?
Plen = MaxWidth ' (Pete) yes, set length to remaining text
ELSE ' no, there is a a trailing space
Plen = MaxWidth + 1 ' (+1 for trailing spaces) set length to include space
END IF
DO ' begin parse loop
IF LEN(WText) <= Plen THEN ' remaining text all that is left?
Parse = MID$(WText, 1, Plen) ' yes, get remaining text
Done = -1 ' parsing is done
ELSE ' no, text still longer than max width
IF INSTR(MID$(WText, 1, Plen), " ") = 0 THEN ' space found in text? (Pete)
Plen = Plen + 1 ' (Pete) no, increment length
ELSE
DO ' begin space search loop
Char = MID$(WText, Plen, 1) ' get last character
IF Char <> " " THEN Plen = Plen - 1 ' if not a space then move back one
LOOP UNTIL Char = " " ' leave when space found
Parse = LEFT$(WText, Plen - 1) ' get parsed string without space at end
END IF
END IF
LOOP UNTIL Char = " " OR Done ' leave when space found or parsing done
END IF
Text(Index) = Parse ' save the parsed text
IF NOT Done THEN WText = MID$(WText, Plen + 1, LEN(WText)) ' remove parsed text from string
LOOP UNTIL Done ' leave when parsing done
Index = 0 ' reset index counter for reporting
END IF
IF Action = 1 THEN ' report number of lines?
ParseText$ = STR$(UBOUND(Text)) ' yes, return number of lines as a string
ELSE ' no, report parsed lines found
Index = Index + 1 ' increment index counter
IF Index > UBOUND(Text) THEN ' have all lines been reported?
ParseText$ = "" ' yes, report nothing remaining
PText = "" ' (Pete) clear for next parsing event
ELSE ' no, parsed text remains
ParseText$ = Text(Index) ' report next line of text
END IF
END IF
END FUNCTIONDrop the function into your own code and parse away.
