That why we made samples, to face those special cases. This problem will be faced with a general sample that contain all needed functions and procedure and shows how to work with them.
I remember an old sample, very popular known as remline.bas that should refresh my memory
Note: I update the qbasic.zip file on my server, you can now find the remline.bas file with the Qbasic compiler.
Don't want to download, here's the sample code on your browser
'
' Microsoft RemLine - Line Number Removal Utility
' Copyright (C) Microsoft Corporation 1985-1990
'
' REMLINE.BAS is a program to remove line numbers from Microsoft Basic
' Programs. It removes only those line numbers that are not the object
' of one of the following statements: GOSUB, RETURN, GOTO, THEN, ELSE,
' RESUME, RESTORE, or RUN.
'
' When REMLINE is run, it will ask for the name of the file to be
' processed and the name of the file or device to receive the
' reformatted output. If no extension is given, .BAS is assumed (except
' for output devices). If filenames are not given, REMLINE prompts for
' file names. If both filenames are the same, REMLINE saves the original
' file with the extension .BAK.
'
' REMLINE makes several assumptions about the program:
'
' 1. It must be correct syntactically, and must run in BASICA or
' GW-BASIC interpreter.
' 2. There is a 400 line limit. To process larger files, change
' MaxLines constant.
' 3. The first number encountered on a line is considered a line
' number; thus some continuation lines (in a compiler-specific
' construction) may not be handled correctly.
' 4. REMLINE can handle simple statements that test the ERL function
' using relational operators such as =, <, and >. For example,
' the following statement is handled correctly:
'
' IF ERL = 100 THEN END
'
' Line 100 is not removed from the source code. However, more
' complex expressions that contain the +, -, AND, OR, XOR, EQV,
' MOD, or IMP operators may not be handled correctly. For example,
' in the following statement REMLINE does not recognize line 105
' as a referenced line number and removes it from the source code:
'
' IF ERL + 5 = 105 THEN END
'
' If you do not like the way REMLINE formats its output, you can modify
' the output lines in SUB GenOutFile. An example is shown in comments.
DEFINT A-Z
' Function and Subprocedure declarations
DECLARE FUNCTION GetToken$ (Search$, Delim$)
DECLARE FUNCTION StrSpn% (InString$, Separator$)
DECLARE FUNCTION StrBrk% (InString$, Separator$)
DECLARE FUNCTION IsDigit% (Char$)
DECLARE SUB GetFileNames ()
DECLARE SUB BuildTable ()
DECLARE SUB GenOutFile ()
DECLARE SUB InitKeyTable ()
' Global and constant data
CONST TRUE = -1
CONST false = 0
CONST MaxLines = 400
DIM SHARED LineTable!(MaxLines)
DIM SHARED LineCount
DIM SHARED Seps$, InputFile$, OutputFile$, TmpFile$
' Keyword search data
CONST KeyWordCount = 9
DIM SHARED KeyWordTable$(KeyWordCount)
KeyData:
DATA THEN, ELSE, GOSUB, GOTO, RESUME, RETURN, RESTORE, RUN, ERL, ""
' Start of module-level program code
Seps$ = " ,:=<>()" + CHR$(9)
InitKeyTable
GetFileNames
ON ERROR GOTO FileErr1
OPEN InputFile$ FOR INPUT AS 1
ON ERROR GOTO 0
COLOR 7: PRINT "Working"; : COLOR 23: PRINT " . . .": COLOR 7: PRINT
BuildTable
CLOSE #1
OPEN InputFile$ FOR INPUT AS 1
ON ERROR GOTO FileErr2
OPEN OutputFile$ FOR OUTPUT AS 2
ON ERROR GOTO 0
GenOutFile
CLOSE #1, #2
IF OutputFile$ <> "CON" THEN CLS
END
FileErr1:
CLS
PRINT " Invalid file name": PRINT
INPUT " New input file name (ENTER to terminate): ", InputFile$
IF InputFile$ = "" THEN END
FileErr2:
INPUT " Output file name (ENTER to print to screen) :", OutputFile$
IF (OutputFile$ = "") THEN OutputFile$ = "CON"
IF TmpFile$ = "" THEN
RESUME
ELSE
TmpFile$ = ""
RESUME NEXT
END IF
'
' BuildTable:
' Examines the entire text file looking for line numbers that are
' the object of GOTO, GOSUB, etc. As each is found, it is entered
' into a table of line numbers. The table is used during a second
' pass (see GenOutFile), when all line numbers not in the list
' are removed.
' Input:
' Uses globals KeyWordTable$, KeyWordCount, and Seps$
' Output:
' Modifies LineTable! and LineCount
'
SUB BuildTable STATIC
DO WHILE NOT EOF(1)
' Get line and first token
LINE INPUT #1, InLin$
Token$ = GetToken$(InLin$, Seps$)
DO WHILE (Token$ <> "")
FOR KeyIndex = 1 TO KeyWordCount
' See if token is keyword
IF (KeyWordTable$(KeyIndex) = UCASE$(Token$)) THEN
' Get possible line number after keyword
Token$ = GetToken$("", Seps$)
' Check each token to see if it is a line number
' (the LOOP is necessary for the multiple numbers
' of ON GOSUB or ON GOTO). A non-numeric token will
' terminate search.
DO WHILE (IsDigit(LEFT$(Token$, 1)))
LineCount = LineCount + 1
LineTable!(LineCount) = VAL(Token$)
Token$ = GetToken$("", Seps$)
IF Token$ <> "" THEN KeyIndex = 0
LOOP
END IF
NEXT KeyIndex
' Get next token
Token$ = GetToken$("", Seps$)
LOOP
LOOP
END SUB
'
' GenOutFile:
' Generates an output file with unreferenced line numbers removed.
' Input:
' Uses globals LineTable!, LineCount, and Seps$
' Output:
' Processed file
'
SUB GenOutFile STATIC
' Speed up by eliminating comma and colon (can't separate first token)
Sep$ = " " + CHR$(9)
DO WHILE NOT EOF(1)
LINE INPUT #1, InLin$
IF (InLin$ <> "") THEN
' Get first token and process if it is a line number
Token$ = GetToken$(InLin$, Sep$)
IF IsDigit(LEFT$(Token$, 1)) THEN
LineNumber! = VAL(Token$)
FoundNumber = false
' See if line number is in table of referenced line numbers
FOR index = 1 TO LineCount
IF (LineNumber! = LineTable!(index)) THEN
FoundNumber = TRUE
END IF
NEXT index
' Modify line strings
IF (NOT FoundNumber) THEN
Token$ = SPACE$(LEN(Token$))
MID$(InLin$, StrSpn(InLin$, Sep$), LEN(Token$)) = Token$
END IF
' You can replace the previous lines with your own
' code to reformat output. For example, try these lines:
'TmpPos1 = StrSpn(InLin$, Sep$) + LEN(Token$)
'TmpPos2 = TmpPos1 + StrSpn(MID$(InLin$, TmpPos1), Sep$)
'
'IF FoundNumber THEN
' InLin$ = LEFT$(InLin$, TmpPos1 - 1) + CHR$(9) + MID$(InLin$, TmpPos2)
'ELSE
' InLin$ = CHR$(9) + MID$(InLin$, TmpPos2)
'END IF
END IF
END IF
' Print line to file or console (PRINT is faster than console device)
IF OutputFile$ = "CON" THEN
PRINT InLin$
ELSE
PRINT #2, InLin$
END IF
LOOP
END SUB
'
' GetFileNames:
' Gets a file name by prompting the user.
' Input:
' User input
' Output:
' Defines InputFiles$ and OutputFiles$
'
SUB GetFileNames STATIC
CLS
PRINT " Microsoft RemLine: Line Number Removal Utility"
PRINT " (.BAS assumed if no extension given)"
INPUT " Input file name (ENTER to terminate): ", InputFile$
IF InputFile$ = "" THEN END
INPUT " Output file name (ENTER to print to screen): ", OutputFile$
IF (OutputFile$ = "") THEN OutputFile$ = "CON"
IF INSTR(InputFile$, ".") = 0 THEN
InputFile$ = InputFile$ + ".BAS"
END IF
IF INSTR(OutputFile$, ".") = 0 THEN
SELECT CASE OutputFile$
CASE "CON", "SCRN", "PRN", "COM1", "COM2", "LPT1", "LPT2", "LPT3"
EXIT SUB
CASE ELSE
OutputFile$ = OutputFile$ + ".BAS"
END SELECT
END IF
DO WHILE InputFile$ = OutputFile$
TmpFile$ = LEFT$(InputFile$, INSTR(InputFile$, ".")) + "BAK"
ON ERROR GOTO FileErr1
NAME InputFile$ AS TmpFile$
ON ERROR GOTO 0
IF TmpFile$ <> "" THEN InputFile$ = TmpFile$
LOOP
END SUB
'
' GetToken$:
' Extracts tokens from a string. A token is a word that is surrounded
' by separators, such as spaces or commas. Tokens are extracted and
' analyzed when parsing sentences or commands. To use the GetToken$
' function, pass the string to be parsed on the first call, then pass
' a null string on subsequent calls until the function returns a null
' to indicate that the entire string has been parsed.
' Input:
' Search$ = string to search
' Delim$ = String of separators
' Output:
' GetToken$ = next token
'
FUNCTION GetToken$ (Search$, Delim$) STATIC
' Note that SaveStr$ and BegPos must be static from call to call
' (other variables are only static for efficiency).
' If first call, make a copy of the string
IF (Search$ <> "") THEN
BegPos = 1
SaveStr$ = Search$
END IF
' Find the start of the next token
NewPos = StrSpn(MID$(SaveStr$, BegPos, LEN(SaveStr$)), Delim$)
IF NewPos THEN
' Set position to start of token
BegPos = NewPos + BegPos - 1
ELSE
' If no new token, quit and return null
GetToken$ = ""
EXIT FUNCTION
END IF
' Find end of token
NewPos = StrBrk(MID$(SaveStr$, BegPos, LEN(SaveStr$)), Delim$)
IF NewPos THEN
' Set position to end of token
NewPos = BegPos + NewPos - 1
ELSE
' If no end of token, return set to end a value
NewPos = LEN(SaveStr$) + 1
END IF
' Cut token out of search string
GetToken$ = MID$(SaveStr$, BegPos, NewPos - BegPos)
' Set new starting position
BegPos = NewPos
END FUNCTION
'
' InitKeyTable:
' Initializes a keyword table. Keywords must be recognized so that
' line numbers can be distinguished from numeric constants.
' Input:
' Uses KeyData
' Output:
' Modifies global array KeyWordTable$
'
SUB InitKeyTable STATIC
RESTORE KeyData
FOR Count = 1 TO KeyWordCount
READ KeyWord$
KeyWordTable$(Count) = KeyWord$
NEXT
END SUB
'
' IsDigit:
' Returns true if character passed is a decimal digit. Since any
' Basic token starting with a digit is a number, the function only
' needs to check the first digit. Doesn't check for negative numbers,
' but that's not needed here.
' Input:
' Char$ - initial character of string to check
' Output:
' IsDigit - true if within 0 - 9
'
FUNCTION IsDigit (Char$) STATIC
IF (Char$ = "") THEN
IsDigit = false
ELSE
CharAsc = ASC(Char$)
IsDigit = (CharAsc >= ASC("0")) AND (CharAsc <= ASC("9"))
END IF
END FUNCTION
'
' StrBrk:
' Searches InString$ to find the first character from among those in
' Separator$. Returns the index of that character. This function can
' be used to find the end of a token.
' Input:
' InString$ = string to search
' Separator$ = characters to search for
' Output:
' StrBrk = index to first match in InString$ or 0 if none match
'
FUNCTION StrBrk (InString$, Separator$) STATIC
Ln = LEN(InString$)
BegPos = 1
' Look for end of token (first character that is a delimiter).
DO WHILE INSTR(Separator$, MID$(InString$, BegPos, 1)) = 0
IF BegPos > Ln THEN
StrBrk = 0
EXIT FUNCTION
ELSE
BegPos = BegPos + 1
END IF
LOOP
StrBrk = BegPos
END FUNCTION
'
' StrSpn:
' Searches InString$ to find the first character that is not one of
' those in Separator$. Returns the index of that character. This
' function can be used to find the start of a token.
' Input:
' InString$ = string to search
' Separator$ = characters to search for
' Output:
' StrSpn = index to first nonmatch in InString$ or 0 if all match
'
FUNCTION StrSpn% (InString$, Separator$) STATIC
Ln = LEN(InString$)
BegPos = 1
' Look for start of a token (character that isn't a delimiter).
DO WHILE INSTR(Separator$, MID$(InString$, BegPos, 1))
IF BegPos > Ln THEN
StrSpn = 0
EXIT FUNCTION
ELSE
BegPos = BegPos + 1
END IF
LOOP
StrSpn = BegPos
END FUNCTION
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