Please tell me where am i wrong, i couldn't fine my mistake in 2 programs. I try to use recursive in pascal.
This one is running but it gives me wrong resuts
program fatorial;
var
n: integer;
function f(n: longint): longint;
begin
if((n=0) or (n=1)) then
f:=1
else
*f:= n*f(n-1);*
read(f);
end;
begin
write('n:='); read(n);
f(n);
write('result:', f(n));
readln;
end.
This one told me "Error: illegal expression" but i don't know how to fix it
program Greatest_common_divisor;
var
gcd,p,q: integer;
r:=real;
begin
write('p:'); read(p);
write('q:'); read(q);
r:= p mod q;
if r <> o then
begin
p:=q;
q:=r
*gcv:= gcv(q,r);*
end;
write('Greatest common divisor:', gcv(p.q));
readln;
end.
You should not read f in the function.
You should write a function rather than use the internal function gcv()
First question:
I think reading f in the function isn't correct.
But the second question:
Don't use := in the command: r:=real; , only :
o and gcv are what kind of variables? You didn't identify o and gcv after var .
Put ; after q:=r
Related
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.
I'm following an internet course on the basics of programming. After making a diagram I convert it to code, right now this is PASCAL language.
I'm having a problem with procedures and can't find an answer, nor in the course, nor with some google-ing.
I want to get a variavble back form a procedure. Right now iIhave a working piece of code but I think this is not the good way of working. Here's an extract of the code:
program WELKEWAGEN;
// declare your variables here
var T, N, KM, vari, prijsDW, prijsBW, jrenGEBR, taksDW, taksBW, prijsB, verbrBW, prijsD, verbrDW : real;
procedure OPHALEN(para : string);
begin
repeat
writeln('geef de ', para , ' op');
readln(vari);
until (vari > 0);
end;
begin
//this is the main program but there is more code ofcourse
OPHALEN('prijs benzinewagen');
prijsBW := vari;
//...
end.
Now the internet course says I should program it like this:
begin
//...
prijsBW := OPHALEN('prijs benzinewagen');
//...
end.
But this is not working.
I get following errors:
WELKEWAGEN.pas(24,14) Error: Incompatible types: got "untyped" expected "Real"
WELKEWAGEN.pas(50) Fatal: There were 1 errors compiling module, stopping
pas(24,14) is this line: prijsBW := OPHALEN('prijs benzinewagen');
Procedures don't return values, so the syntax
prijsBW := OPHALEN('prijs benzinewagen');
is invalid.
If you want to return a value, you need to define a function instead:
function OPHALEN(para : string): Real;
var
Res: Real;
begin
Res := 0;
repeat
writeln('geef de ', para , ' op');
readln(Res);
until (Res > 0);
OPHALEN := Res;
end;
Note that the (bad) global variables you're using mean you don't have to return anything at all, because a procedure can access and change that global variable directly (but you have no way of knowing when the procedure is finished):
procedure OPHALEN(para : string);
begin
vari := 0;
repeat
writeln('geef de ', para , ' op');
readln(vari);
until (vari > 0);
end;
Modern Pascal dialects (such as Delphi and FreePascal) allow a cleaner syntax for the return value of functions by using an automatically declared function result variable of the proper type for you, named Result (because that's what it is - the result of the function):
function OPHALEN(para : string): Real;
begin
Result := 0;
repeat
writeln('geef de ', para , ' op');
readln(Result);
until (Result > 0);
end;
If you need to return multiple values, you can use var parameters, which allow them to be changed inside the function.
procedure OPHALEN(para: string; var RetVal: Real);
begin
RetVal := 0;
repeat
writeln('geef de ', para , ' op');
readln(RetVal);
until (RetVal > 0);
end;
Your original code (and the examples I've provided above) all fail to allow the user to cancel, BTW. There should be some way to exit the loop for the user; otherwise, your code just endlessly loops, writing para to the screen and then waiting for input. This has a tendency to annoy users.
in our last class we defined a couple of functions and procedures in our unit file.
procedure WriteNap(const elo: string; const n: TNap; const uto: string);
begin
Write(elo, Nap2Str(n), uto);
end;
function PredNap(const n: TNap): TNap;
begin
case n of
hetfo: PredNap := vasarnap;
NemNap: PredNap := n;
else
PredNap := Pred(n)
end;
end;
function SuccNap(const n: TNap): TNap;
begin
case n of
NemNap: SuccNap := n;
else
SuccNap := Succ(n)
end;
end;
I have to get rid of the word 'Nap' so that i can just use Pred, Write, Succ in the main program instead of PredNap etc... i tried to create another unit file which uses this unit and contains functions like Succ Pred... didnt really work out..
thanks in advance :)
Declare in somewhere in your file:
var Pred = Function (Const n:TNap):TNap;
And before you do anything in the body of your program, write:
Pred := #PredNap;
What this code does is, it creates a new function pointer with the same signature as your PredNap() and then assign the address of PredNap() to this pointer. So, whenever you call Pred() the actual function that gets called is PredNap(). Hope this helps.
I'm working in Pascal, I don't understand why I'm getting an NZEC (Non Zero Exit Code) error when I'm submitting my problem. On my PC it works perfectly. Can you give me your opinion please?
program super_factor_sum;
var k,i,j,s:longint; f,g:text;
function prim(x:integer):boolean; var d:longint;
begin
prim:=true;
for d:=2 to x div 2 do if x mod d=0 then prim:=false;
end;
begin assign(f,'input.txt'); reset(f); assign(g,'output.txt'); rewrite(g);
while not eof(f) do
begin readln(f,k); s:=0; i:=2;
while (k<>1) or (i<=k) do
begin if (prim(i)) and (k mod i=0) then
begin j:=0;
repeat k:=k div i; j:=j+1;
until k mod i<>0;
s:=s+i*j; i:=i+1;
end
else i:=i+1;
end;
write(s); writeln(g,s);
end;
close(f); close(g);
end.
Avoid NZEC error in Erlang in SPOJ
"module name always has to be tested and the entry point should be function main . For example, after compilation it should be run as tested:main()"
I'm using Pascal. I have a problem when dealing with reading file.
I have a file with integer numbers. My pascal to read the file is:
read(input, arr[i]);
if my file content is 1 2 3 then it's good but if it is 1 2 3 or 1 2 3(enter here) (there is a space or empty line at the end) then my arr will be 1 2 3 0.
From what I can recall read literally reads the file as a stream of characters, of which a blank space and carriage return are, but I believe these should be ignored as you are reading into an integer array. Does your file actually contain a space character between each number?
Another approach would be to use readLn and have the required integers stored as new lines in the file, e.g.
1
2
3
I have tested the problem on Delphi 2009 console applications. Code like this
var
F: Text;
A: array[0..99] of Integer;
I, J: Integer;
begin
Assign(F, 'test.txt');
Reset(F);
I:= -1;
while not EOF(F) do begin
Inc(I);
Read(F, A[I]);
end;
for J:= 0 to I do write(A[J], ' ');
Close(F);
writeln;
readln;
end.
works exactly as you have written. It can be improved using SeekEOLN function that skips all whitespace characters; the next code does not produce wrong additional zero:
var
F: Text;
A: array[0..99] of Integer;
I, J: Integer;
begin
Assign(F, 'test.txt');
Reset(F);
I:= -1;
while not EOF(F) do begin
if not SeekEOLN(F) then begin
Inc(I);
Read(F, A[I]);
end
else Readln(F);
end;
for J:= 0 to I do write(A[J], ' ');
Close(F);
writeln;
readln;
end.
Since all that staff is just a legacy in Delphi, I think it must work in Turbo Pascal.
You could read the string into a temporary and then trim it prior to converting it.
It doesnt hurt to mention basics like what type of Pascal on what platform you're using in order that people can give a specific answer (as the article notes, there isnt a nice way OOTB in many Pascals)
If I recall there was a string function called Val that converts a string to a number...my knowledge of Pascal is a bit rusty (Turbo Pascal v6)
var
num : integer;
str : string;
begin
str := '1234';
Val(str, num); (* This is the line I am not sure of *)
end;
Hope this helps,
Best regards,
Tom.