I am attempting to write a comment stripper in pascal. I run my code and pass it a C source code file and it strips the comments from the file and prints the result to terminal.
I am fairly new to pascal. I am getting some very strange output and I cannot figure out why. The code checks for comments line by line and prints characters one at a time. The comment stripper is printing what seems to be random characters whenever it reaches the start of a new line. I am using pascals Write(Str[i]) function to print characters and WriteLn() once the end of a line is reached.
I have no idea why im receiving weird output. I am running Linux Mint and can compile and run my code, but I receive this strange output. I also tried running my code on a Mac and received a run-time error:
Program Path: ./Assignment1
File Name: lol.c
Runtime error 2 at $00011532
$00011532
$0002F7F6
$000113FD
$00011328
$00000002
Here is my code
program Assignment1;
uses
Sysutils;
var UserFile : TextFile;
TString : String;
OLine : String;
i : integer;
isComment : boolean;
skip : boolean;
begin
{$I+}
WriteLn('Program Path: ', ParamStr(0));
WriteLn('File Name: ', ParamStr(1));
Assign(UserFile, ParamStr(1) + '.c');
Reset(UserFile);
isComment := false;
skip := true;
Repeat
Readln(UserFile, TString);
for i:= 0 to ((Length(TString) - 1)) do
begin
if(skip) then
begin
skip := false;
continue;
end;
if(isComment = false) Then
begin
if(TString[i] = '/') Then
begin
if(TString[i+1] = '/') Then
begin
break;
end
else if(TString[i+1] = '*') Then
begin
isComment := true;
skip := true;
continue;
end;
end;
Write(TString[i]);
if(i = Length(TString) - 1) Then
begin
Write(TString[i + 1]);
end;
end
else
begin
if(TString[i] = '*') Then
begin
if(TString[i + 1] = '/') Then
begin
isComment := false;
skip := true;
continue;
end;
end;
end;
end;
WriteLn();
Until Eof(UserFile);
end.
I receive random characters which range from standard keyboard symbols to unicode blocks such as the ones found here.
Does anyone have any suggestions?
As 500 - Internal Server Error says, Pascal strings are 1-based. Your references to slot zero are returning garbage. If these are 256-byte strings you're getting the length code, I don't recall the memory layout of the pointer-based strings to know what you're getting in that case. You're also losing the last character of every string because of this.
Beyond that I see a definite bug: Look at what happens with a line ending in /
I also do not understand this:
if(i = Length(TString) - 1) Then
begin
Write(TString[i + 1]);
end;
It seems to me it's writing an extra character but I'm not sure.
Related
So, I'm new here and I'm new to programming generally. I made this program that I needed for a project (a pascal program using Lazarus) that allows me to get a kind of list generated by replacing * by numbers. What I need is to be able to give it multiple codes to process at once (maximum 10) instead of entering every code at once.
program b;
{$mode objfpc}
{$H+}
uses sysutils;
var
sourcestr: string;
resultstr: string;
n: integer;
begin
writeln('provide a string:');
readln(sourcestr);
for n := 0 to 99 do begin
resultstr := StringReplace(sourcestr, '*', IntToStr(n div 10), []);
resultstr := StringReplace(resultstr, '*', IntToStr(n mod 10), []);
resultStr := resultStr + ':password';
writeln(resultstr);
end;
end.
I hope you could help me with this and thanks in advance.
The code below shows how to replace an arbitrary number of pairs of asterisks by the two substitute characters you are generating.
for n := 0 to 9 do begin
resultstr := sourcestr;
while Pos('*', resultstr) > 0 do begin
stringReplace(resultstr, '*', IntToStr(n div 10), []);
resultstr := StringReplace(resultstr, '*', IntToStr(n mod 10), []);
end;
resultStr := resultStr + ':password';
writeln(resultstr);
end;
It uses the Pos function in a while loop to replace the asterisk pairs. Be aware that the output may not be exactly what you need, because in each generated resultstr you will get the same substitute characters replacing each pair of asterisks, i.e.
with an input of
a ** b ** c
the resultstrs generated will be like
a00b00c
a11b11c
which may not be what you need. If not, changing the code to do what you do need is left as an exercise for the reader, as they say.
Btw, it occurred to me later that maybe you are asking how to input and process several lines'-worth of user input. One way to do that would be to read the lines into a TStringList (see online help) and then process that. Something like:
var
TL : TStringList;
sourcestr : String;
begin
TL := TStringList.Create;
repeat
readln(sourcestr);
if sourcestr <> '' then
TL.Add(sourcestr);
until sourcestr = '';
for i := 0 to TL.Count - 1 do begin
sourcestr := TL[i];
// process sourcestr however you want
end;
TL.Free;
though you could, of course, simply process sourcestr as you go along, in the repeat..until loop.
Im having problems with this code, I have two file of char, one is filed with information about books, and the other is empty, i have to write in SAL some information from S and then show the total of how many books match the first 2 digits of the code and how many are R and how many are T. The code, does write the information form S to Sal, but when its supposed to show the totals it appears ERORR 100 on screen. I read about it and it says that it is a problem with 'Disk read error' and that *This error typically occurs, if you "seed" a non-existent record of a typed file and try to read/write it. *, i really dont undertand.
I've benn trying to figure it out, but I haven't been able to. I notice that if I dont put 'WHILE NOT EOF(S) DO' the error does not appear, but of course i need the while, if someone is able to point out my mistakes i would really apreciate it.
This is the code:
uses crt;
var
i : byte;
s,sal: file of char;
v,l1,l2: char;
cs,cn,cl: integer;
pn,ps,tot: integer;
BEGIN
cs:=0; cn:=0; i:=0; cl:=0;
Assign (s, 'C:\Users\te\Documents\s.txt');
{$I-}
Reset (s);
{$I+}
if IOResult <> 0 then
begin
writeln('Error');
halt(2);
end;
Assign (sal, 'C:\Users\te\Documents\sal.txt');
{$I-}
Rewrite (sal);
IOResult;
{$I+}
if IOResult <> 0 then
halt(2);
writeln('Please write the code of the book, only 2 digits');
read(L1);read(L2);
read(s,v);
while (not eof(s)) do
begin
for i:=1 to 2 do
read(s,v);
if (v = '0') then
begin
read(s,v);
if (v = '1') or (v = '2') then
begin
for i:=1 to 5 do
read(s,v);
if (v = 'R') then
begin
read(s,v);
cs:= cs + 1;
end
else
begin
if (v = 'T') then
begin
cn:= cn + 1;
read(s,v);
end;
end;
while (v <> '-') do
read(s,v);
while (v = '-') do
read(s,v);
if (v = L1) then
begin
write(sal, v);
read(s,v);
if (v = L2) then
begin
write(sal,v);
read(s,v);
cl:= cl + 1;
end;
end;
while ( v <> '/') do
begin
write(sal,v);
read(s,v);
end;
write(sal, '-');
end
else
begin
for i:= 1 to 5 do
read(s,v);
if (v = 'R') then
cs:= cs + 1
else
cn:= cn + 1;
if (v = L1) then
read(s,v);
if (v = L2) then
begin
cl:= cl + 1;
read(s,v);
end;
end;
end
else
begin
for i:= 1 to 5 do
read(s,v);
if (v = 'R') then
cs:= cs + 1
else
cn:= cn + 1;
if (v = L1) then
read(s,v);
if (v = L2) then
begin
cl:= cl + 1;
read(s,v);
end;
end;
end;
tot:= cs + cn;
ps:= (cs * 100) div tot;
pn:= (cn * 100) div tot;
writeln('TOTAL ',cl);
writeln();
writeln(ps,'% and',pn,'%');
The file S content:
02022013Rto kill a mockingbird-1301/02012014Tpeter pan-1001/02032013Thowto-2301/02012012Tmaze runner-1001/02012012Tmaze runner-1001/02012012Tmaze runner-1001/$
I really just need someone else's point of view on this code, I think maybe the algorithm is flawed.
Thanks
(After your edit, i see that your code now compiles w/o error in FPC, so I'm glad you've managed to fix the error yourself)
As this is obviously coursework, I'm not going to fix your code for you and in any case the wayEven so, I'm afraid you are going about this is completely wrong.
Basically, the main thing wrong with your code is that you are trying to control what happens as your read the source file character by character. Quite frankly, that's a hopeless way of trying to do it, because it makes the execution flow unnecessarily complicated and littered with ifs, buts and loops. It also requires you to keep mental track of what you are trying to do at any given step, and the resulting code is inherently not self-documenting - imagine if you came back to your code in six months, could you tell at a glance how it works and what it does? I certsinly couldn't personally.
You need to break the task down in a different way. Instead of analysing the problem from the bottom up ("If I read this character next, then what I need to do next is ...') do it from the top down: Although your input file is a file of char, it contains a series of strings, separated by a / character and finally terminated by a $ (but this terminator does not really matter). So what you need to do is to read these strings one-by-one; once you've got one, check whether it's the one you're looking for: if it is. process it however you need to, otherwise read the next one until you reach the end of the file.
Once you have successfully read one of the book strings, you can then split it up into the various fields it's composed of. The most useful function for doing this splitting is probably Copy, which lets you extract substrings from a string - look it up in the FPC help. I've included functions ExtractTitle and ExtractPreamble which show you what you need to do to write similar functions to extract the T/R code and the numeric code which follows the hyphen. Btw, if you need to ask a similar q in the future, it would be very helpful if you include a description of the layout and meaning of the various fields in the file.
So, what I'm going to show you is how to read the series of strings in your S.Txt by building them character-by-character. In the code below, I do this using a function GetNextBook which I hope is reasonable self-explanatory. The code uses this function in a while loop to fill the BookRecord string variable. Then, it simply writes the BookRecord to the console. What your code should do, of course, is to process the BookRecord contents to see if it is the one you are looking for and then do whether the remainder of your task is.
I hope you will agree that the code below is a lot clearer, a lot shorter and will be a lot easier to extend in future than the code in your q. They key to structuring a program this way is to break the program's task into a series of functions and procedures which each perform a single sub-task. Writing the program that way makes it easier to "re-wire" the program to change what it does, without having to rewrite the innards of the functions/procedures.
program fileofcharproject;
uses crt;
const
sContents = '02022013Rto kill a mockingbird-1301/02012014Tpeter pan-1001/02032013Thowto-2301/02012012Tmaze runner-1001/02012012Tmaze runner-1001/02012012Tmaze runner-1001/$';
InputFileName = 'C:\Users\MA\Documents\S.Txt';
OutputFileName = 'C:\Users\MA\Documents\Sal.Txt';
type
CharFile = File of Char; // this is to permit a file of char to be used
// as a parameter to a function/procedure
function GetNextBook(var S : CharFile) : String;
var
InputChar : Char;
begin
Result := '';
InputChar := Chr(0);
while not Eof(S) do begin
Read(S, InputChar);
// next, check that the char we've read is not a '/'
// if it is a '/' then exit this while loop
if (InputChar <> '/') then
Result := Result + InputChar
else
Break;
end;
end;
function ExtractBookTitle(BookRecord : String) : String;
var
p : Integer;
begin
Result := Copy(BookRecord, 10, Length(BookRecord));
p := Pos('-', Result);
if p > 0 then
Result := Copy(Result, 1, p - 1);
end;
procedure AddToOutputFile(var OutputFile : CharFile; BookRecord : String);
var
i : Integer;
begin
for i := 1 to Length(BookRecord) do
write(OutputFile, BookRecord[i]);
write(OutputFile, '/');
end;
function ExtractPreamble(BookRecord : String) : String;
begin
Result := Copy(BookRecord, 1, 8);
end;
function TitleMatches(PartialTitle, BookRecord : String) : Boolean;
begin
Result := Pos(PartialTitle, ExtractBookTitle(BookRecord)) > 0;
end;
var
i : Integer; //byte;
s,sal: file of char;
l1,l2: char;
InputChar : Char;
BookFound : Boolean;
cs,cn,cl: integer;
pn,ps,tot: integer;
Contents : String;
BookRecord : String;
PartialTitle : String;
begin
// First, create S.Txt so we don't have to make any assumptions about
// its contents
Contents := sContents;
Assign(s, InputFileName);
Rewrite(s);
for i := 1 to Length(Contents) do begin
write(s, Contents[i]); // writes the i'th character of Contents to the file
end;
Close(s);
cs:=0; cn:=0; i:=0; cl:=0;
// Open the input file
Assign (s, InputFileName);
{$I-}
Reset (s);
{$I+}
if IOResult <> 0 then
begin
writeln('Error');
halt(2);
end;
// Open the output file
Assign (sal, OutputFileName);
{$I-}
Rewrite (sal);
IOResult;
{$I+}
if IOResult <> 0 then
halt(2);
// the following reads the BookRecords one-by-one and copies
// any of them which match the partial title to sal.txt
writeln('Enter part of a book title, followed by [Enter]');
readln(PartialTitle);
while not Eof(s) do begin
BookRecord := GetNextBook(S);
writeln(BookRecord);
writeln('Preamble : ', ExtractPreamble(BookRecord));
writeln('Title : ', ExtractBookTitle(BookRecord));
if TitleMatches(PartialTitle, BookRecord) then
AddToOutputFile(sal, BookRecord);
end;
// add file '$' to sal.txt
write(sal, '$');
Close(sal);
Close(s);
writeln('Done, press any key');
readln;
end.
Got me stumped: on Windows, Free Pascal
{... writes text lines to PdfTmp, then ...}
close(PdfTmp);
reset(PdfTmp);
while not eof(PdfTmp) do begin
readln(PdfTmp,InpLine);
writeln(ProdFile,InpLine);
end;
close(PdfTmp);
I've verified that the PdfTmp file is written with the text, but the eof() function returns true on the first call, thus the while block is never executed.
I tried all kinds of tricks with surrounding code to determine whatever else might be causing the failure, including updating my FPC compiler, to no avail. Tests confirm it is the improper eof() function result.
The same code works properly on a Mac. (FreePascal supports various platforms.)
Any other poor soul out there had this evil befall and stall out a nice project? If so, how was it fixed, if it was?
Here's how I solved the problem:
{}
{$ifdef WIN}
procedure starttext (var F :file; var Feof :boolean);
begin
reset(F,1); Feof := filesize(F) = 0;
end;
procedure gettext (var F :file; Feoln :array of byte; var Feof :boolean; var S :string);
{ gets the next text line from F into S. Returns false at end of file.
It returns the last string and sets eof if there are no additional strings.}
var endline, endfile :boolean; P, R :longint; C, D :byte;
begin
S := '';
endline := false;
endfile := false;
repeat
P := filepos(F);
blockread(F,C,1,R);
if R = 0 then begin
endline := true;
endfile := true; end
else begin
P := P + 1;
if C = Feoln[0] then begin
if high(Feoln) > 0 then begin
blockread(F,D,1,R);
if (R <> 0) then begin
if D = Feoln[1] then begin
endline := true;
P := P + 1; end
else
seek(F, P);
end else
P := P + 1;
end else
endline := true;
end else
S := S + chr(C);
endfile := P = (filesize(F));
end;
until
(endline = true) or (endfile = true);
Feof := endfile;
end;
{$endif}
{}
...
{}
close(PdfTmp);
{$ifdef OSX}
reset(PdfTmp);
while not eof(PdfTmp) do begin
readln(PdfTmp,InpLine);
putpdfln(InpLine);
end;
close(PdfTmp);
{$endif}
{$ifdef WIN}
assign(PdfWrk,FileID+'.$$$'); {same file as PdfTmp}
starttext(PdfWrk,eofPdfWrk);
while not eofPdfWrk do begin
gettext(PdfWrk, [13,10], eofPdfWrk, InpLine);
putpdfln(InpLine);
end;
close(PdfWrk);
{$endif}
{}
...
I abandoned the idea that Windows was a viable product when I realized Microsoft had failed to follow IBM's instructions for how to handle interrupts which they published with the first IBM-PC. This failure still plagues the monstrous ill-conceived class structure of Windows; and leads to that enigmatic occasional glitch we've all experienced in Windows applications.
Personally, I don't believe an operating system should be built with classes, which impose an unnecessary overhead for process code that will be needed only once in the system (which if properly done will be true for all the code in the OS). A good API would suffice.
I am working on a particular scenario, where I have to read from a Text File, parse it, extract meaningful information from it, perform SQL queries with the information and then produce a reponse, output file.
I have about 3000 lines of code. Everything is working as expected. However I have been thinking of a connendrum that could possibly dissrupt my project.
The text file being read (lets call it Text.txt) may consist of a single line or multiple lines.
In my case, a 'line' is identified by its segment name - say ISA, BHT, HB, NM1, etc... each segment ending is identified by a special character '~'.
Now if the file consists of multiple lines (such that each line corresponds to a single segment); say:-
ISA....... ~
NM1....... ~
DMG....... ~
SE........ ~
and so on.... then my code essentially reads each 'line' (i.e. each segment), one at a time and stores it into a temp buffer using the following command :-
ReadLn(myFile,buffer);
and then performs evaluations based on each line. Produces the desired output. No problems.
However the issue is... what if the file consists of only a single line (consisting of multiple segments), represented as:-
ISA....... ~NM1....... ~DMG....... ~SE........ ~
then with my ReadLine command I read the entire line instead of each segment, one at a time. This doesn't work for my code.
I was thinking about creating an if, else statement pair...which is based on how many lines my Txt.txt file consists of..such as:-
if line = 1:-
then extract each segment at a time...seperated by the special character '~'
perform necessary tasks (3000 lines of code)
else if line > 1:-
then extract each line at a time (corresponding to each segment)
perform necessary tasks (3000 lines of code).
now the 3000 lines of code is repeated twice and I don't find it elegant to copy and paste all of that code twice.
I would appreciate if I could get some feedback on how to possibly solve this issue, such that, regardless of a one-line file or multiple-line file...when i proceed to evaluate, i only use one segment at a time.
There are many possible ways of doing this. Which is best for you might depend on how long these files are and how important performance is.
A simple solution is to just read characters one at a time until you hit your tilde delimiter.
The routine ReadOneItem below shows how this can be done.
procedure TForm1.Button1Click(Sender: TObject);
const
FileName = 'c:\kuiper\test2.txt';
var
MyFile : textfile;
Buffer : string;
// Read one item from text file MyFile.
// Load characters one at a time.
// Ignore CR and LF characters
// Stop reading at end-of-file, or when a '~' is read
function ReadOneItem : string;
var
C : char;
begin
Result := '';
// loop continues until break
while true do
begin
// are we at the end-of-file? If so we're done
if eof(MyFile) then
break;
// read in the next character
read ( MyFile, C );
// ignore CR and LF
if ( C = #13 ) or ( C = #10 ) then
{do nothing}
else
begin
// add the character to the end
Result := Result + C;
// if this is the delimiter then stop reading
if C = '~' then
break;
end;
end;
end;
begin
assignfile ( MyFile, FileName );
reset ( MyFile );
try
while not EOF(MyFile) do
begin
Buffer := ReadOneItem;
Memo1 . Lines . Add ( Buffer );
end;
finally
closefile ( MyFile );
end;
end;
I would use a file mapping via the Win32 API CreateFileMapping() and MapViewOfFile() functions, and then just parse the raw data as-is, scanning for ~ characters and ignoring any line breaks you might encounter in between each segment. For example:
var
hFile: THandle;
hMapping: THandle;
pView: Pointer;
FileSize, I: DWORD;
pSegmentStart, pSegmentEnd: PAnsiChar;
sSegment: AnsiString;
begin
hFile := CreateFile('Path\To\Text.txt', GENERIC_READ, FILE_SHARE_READ, nil, OPEN_EXISTING, 0, 0);
if hFile = INVALID_HANDLE_VALUE then RaiseLastOSError;
try
FileSize := GetFileSize(hFile, nil);
if FileSize = INVALID_FILE_SIZE then RaiseLastOSError;
if FileSize > 0 then
begin
hMapping := CreateFileMapping(hFile, nil, PAGE_READONLY, 0, FileSize, nil);
if hMapping = 0 then RaiseLastOSError;
try
pView := MapViewOfFile(hMapping, FILE_MAP_READ, 0, 0, FileSize);
if pView = nil then RaiseLastOSError;
try
pSegmentStart := PAnsiChar(pView);
pSegmentEnd := pSegmentStart;
I := 0;
while I < FileSize do
begin
if pSegmentEnd^ = '~' then
begin
SetString(sSegment, pSegmentStart, Integer(pSegmentEnd-pSegmentStart));
// use sSegment as needed...
pSegmentStart := pSegmentEnd + 1;
Inc(I);
while (I < FileSize) and (pSegmentStart^ in [#13, #10]) do
begin
Inc(pSegmentStart);
Inc(I);
end;
pSegmentEnd := pSegmentStart;
end else
begin
Inc(pSegmentEnd);
Inc(I);
end;
end;
if pSegmentEnd > pSegmentStart then
begin
SetString(sSegment, pSegmentStart, Integer(pSegmentEnd-pSegmentStart));
// use sSegment as needed...
end;
finally
UnmapViewOfFile(pView);
end;
finally
CloseHandle(hMapping);
end;
end;
finally
CloseHandle(hFile);
end;
I want to develop a setup package for conditionally upgrading an existing package. I want to check the existing software version against to-be-installed version. In order to do that, I have to compare the version strings.
How can I convert the string value to a numerical value in a Inno setup script?
RegQueryStringValue(HKEY_LOCAL_MACHINE, 'Software\Blah blah', 'Version', version)
version = 'V1.R2.12';
numVersion := ??string_to_numerical_value??(version);
This is a little more tricky, as you would want to handle versions like 'V1.R2.12' and 'V0.R15.42' correctly - with the simple conversion in the other answer you would get 1212 and 1542, which would not compare the way you would expect.
You need to decide how big each part of the version number can be, and multiply the parts by that value to get a correct end number. Something like this:
[Code]
function string_to_numerical_value(AString: string; AMaxVersion: LongWord): LongWord;
var
InsidePart: boolean;
NewPart: LongWord;
CharIndex: integer;
c: char;
begin
Result := 0;
InsidePart := FALSE;
// this assumes decimal version numbers !!!
for CharIndex := 1 to Length(AString) do begin
c := AString[CharIndex];
if (c >= '0') and (c <= '9') then begin
// new digit found
if not InsidePart then begin
Result := Result * AMaxVersion + NewPart;
NewPart := 0;
InsidePart := TRUE;
end;
NewPart := NewPart * 10 + Ord(c) - Ord('0');
end else
InsidePart := FALSE;
end;
// if last char was a digit the last part hasn't been added yet
if InsidePart then
Result := Result * AMaxVersion + NewPart;
end;
You can test this with the following code:
function InitializeSetup(): Boolean;
begin
if string_to_numerical_value('V1.R2.12', 1) < string_to_numerical_value('V0.R15.42', 1) then
MsgBox('Version ''V1.R2.12'' is not as recent as version ''V0.R15.42'' (false)', mbConfirmation, MB_OK);
if string_to_numerical_value('V1.R2.12', 100) > string_to_numerical_value('V0.R15.42', 100) then
MsgBox('Version ''V1.R2.12'' is more recent than version ''V0.R15.42'' (true)', mbConfirmation, MB_OK);
Result := FALSE;
end;
Whether you pass 10, 100 or 1000 for AMaxVersion depends on the number and range of your version number parts. Note that you must not overflow the LongWord result variable, which has a maximum value of 2^32 - 1.
I haven't tried that (and my Pascal knowledge is a bit rusty), but something like the following should work:
function NumericVersion(s: String): Integer;
var
i: Integer;
s1: String;
begin
s1 := '';
for i := 0 to Length(s)-1 do
if (s[i] >= '0') and (s[i] <= '9') then
s1 := s1 + s[i];
Result := StrToIntDef(s1, 0);
end;
Please not that you'll have to play with the start and end value for i as I'm not sure whether it is zero-based or not (s[0] may contain the length of the string if it is a "Pascal String").
I've implemented two version strings (actually one string and one dword value) in the registry to overcome complexity.
displayversion="v1.r1.0"
version="10100" (=1*10^4 + 1*10^2 + 0*10^0)
That's simple. Though not an answer to this question, however one might think the other way around when faced with complexity, which could be avoided in a simpler way.