I was trying to use same printing procedure for two types of arrays(1st arry length was 10, 2nd array length was 15).
I could not find any solution over internet. Did any one have any solution for this problem.
this is the Two arrays
program pp1;
const
m=10;
n=15;
type
matrix1=array[1..m] of integer;
matrix2=array[1..n] of integer;
var
m1:matrix1;
m2:matrix2;
this is the method which it tried. in method 'x' mens the length of the array.
procedure writeMatrix(var data: array of integer ;x:integer);
var
j:integer;
begin
for j:=1 to x do
begin
write(data[j]:3);
end;
end;
my main method
begin
writeMatrix(m1,10);
writeMatrix(m2,10);
end.
How can i use the same this writeMatrix method to print both of the arrays.. Is there any stranded way to do it.
As I said in my comment before, your implementation is fine, but you have to put something in your matrix before printing it, or you will get a bunch of zeroes in the screen (in the best).
Try this:
program pp1;
const
m=10;
n=15;
type
matrix1=array[1..m] of integer;
matrix2=array[1..n] of integer;
var
m1:matrix1;
m2:matrix2;
procedure fillMatrix(var data:array of integer; x:integer);
var
j:integer;
begin
for j:= 1 to x do begin
data[j]:=j;
end;
end;
procedure writeMatrix(var data: array of integer; x:integer);
var
j:integer;
begin
for j:=1 to x do
begin
write(data[j]:3);
end;
end;
begin
fillMatrix(m1,10);
fillMatrix(m2,10);
writeMatrix(m1,10);
writeMatrix(m2,10);
readln;
readln;
end.
Hint: consider avoid using global variables, m1 and m2 in this case should be declared in the main program.
How can i use the same this writeMatrix method to print both of the arrays.. Is there any stranded way to do it.
Yes, there is a standard way to this. It is called conformant-array parameters. It is standardized in (level 1) of the ISO standard 7185 (Standard “Unextended” Pascal). It looks like this:
procedure print(protected matrix: array[
columnMinimum..columnMaximum: integer;
rowMinimum..rowMaximum: integer
] of integer);
const
totalWidth = 6;
var
x: type of columnMinimum;
y: type of rowMinimum;
begin
for y := rowMinimum to rowMaximum do
begin
for x := columnMinimum to columnMaximum do
begin
write(matrix[x, y]:totalWidth);
end;
writeLn;
end;
end;
It’s as if there were additional const values, but they are dynamic depending on the passed matrix. This code furthermore uses type inquiries (type of …) and the protected modifier, both defined in ISO 10206 (Extended Pascal) which builds on top of ISO 7185. In EP you could and would also consider schemata to pass such data as parameters.
Related
This question already has an answer here:
How Can I Replace StringList.Sort with a Stable Sort in Delphi?
(1 answer)
Closed 1 year ago.
I have the following (simplified) class definition:
TMyObject = class
private
FDoubleValue: Double;
FText: string;
protected
public
constructor Create(ADoubleValue: Double; AText: string);
property DoubleValue: Double read FDoubleValue write FDoubleValue;
property Text: string read FText write FText;
end;
The following sample code, shows how I am sorting the TObjectList<TMyObject> (FMyObjects) and displaying them in a TListBox.
constructor TfrmMain.Create(AOwner: TComponent);
begin
inherited;
FMyObjects := TObjectList<TMyObject>.Create;
FMyObjects.OwnsObjects := true; // Default but for clarity
end;
destructor TfrmMain.Destroy;
begin
FMyObjects.Free;
inherited;
end;
procedure TfrmMain.FormCreate(Sender: TObject);
var
ii: Integer;
begin
FMyObjects.Add(TMyObject.Create(100.00, 'Item 1'));
FMyObjects.Add(TMyObject.Create(200.00, 'Item 2'));
FMyObjects.Add(TMyObject.Create(300.00, 'Item 3')); // Duplicate sort value
FMyObjects.Add(TMyObject.Create(300.00, 'Item 4')); // Duplicate sort value
FMyObjects.Add(TMyObject.Create(400.00, 'Item 5'));
ObjectsToListBox;
end;
procedure TfrmMain.SortList;
var
Comparer: IComparer<TMyObject>;
begin
Comparer := TDelegatedComparer<TMyObject>.Create(
function(const MyObject1, MyObject2: TMyObject): Integer
begin
result := CompareValue(MyObject1.DoubleValue, MyObject2.DoubleValue, 0);
end);
FMyObjects.Sort(Comparer);
end;
procedure TfrmMain.ObjectsToListBox;
var
ii: Integer;
begin
ListBox1.Items.Clear;
for ii := 0 to FMyObjects.Count - 1 do
ListBox1.Items.Add(Format('%d - %.1f - %s', [ii, FMyObjects[ii].DoubleValue,
FMyObjects[ii].Text]));
end;
procedure TfrmMain.Button1Click(Sender: TObject);
begin
SortList;
ObjectsToListBox;
end;
Every time Button1 is clicked (and the list sorted), FMyObjects[2] (Item3) and FMyObjects[3] ('Item4') swap position in the list. In my "real world" (drawing) application this is undesirable.
I also experimented with different values for Epsilon in the CompareValue function call and also a different implementation of the anonymous function (comparing values and returning 1, -1 or 0), but neither seems to make a difference.
Am I missing something (e.g. a property that controls this behavior) or is this "by design" and it cannot be prevented?
This is by design. The internally used Quicksort implementation is not a stable one, so reorder of equal items is expected. To make the sort stable you need to extend your comparer to take that into account. F.i. you can compare the Text properties when the DoubleValue properties are equal.
Can anyone share what are some common Delphi examples of a function that takes a number
and returns a number that is not so obvious?
For example :
function GetNumber(const aSeed: Integer): Integer;
begin
Result := ((aSeed+5) * aSeed) + 15;
end;
So let's say the user knows that sending aSeed = 21 gives 561
and aSeed = 2, gives 29
and so on...
is there a function that makes it hard to reverse engineer the code,
even if one can generate a large number sets of Seed/Result ?
(hard : I do not mean impossible, just need to be non-trivial)
Preferably a function that does not allow in function result exceeding the
Integer result as well.
In any case, if you are not sure whether it's hard/impossible to reverse,
do feel free to share what you have.
some other requirements:
the same input always results in the same output; cannot have Random output
the same output regardless of platform: windows/android/mac/ios
won't result in some extraordinary big number (fit in Integer)
Using a hash is a very good way to achieve what you want. Here is an example that takes an integer, converts it to a string, appends it to a salt, computes the MD5 and returns the integer corresponding to the first 4 bytes:
uses
System.Hash;
function GetHash(const s: string): TBytes;
var
MD5: THashMD5;
begin
MD5 := THashMD5.Create;
MD5.Update(TEncoding.UTF8.GetBytes(s));
Result := MD5.HashAsBytes;
end;
function GetNumber(Input: Integer): Integer;
var
Hash: TBytes;
p: ^Integer;
begin
Hash := GetHash('secret' + IntToStr(Input));
P := #Hash[0];
Result := Abs(P^);
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
ShowMessage(IntToStr(GetNumber(1))); // 996659739
ShowMessage(IntToStr(GetNumber(2))); // 939216101
ShowMessage(IntToStr(GetNumber(3))); // 175456750
end;
I started learning Pascal :) and I was interested on making a kind of Euromillion... However, I don't know how to forbid the same numbers or stars...
I thought this (below) would solve it... But it didn't... Help?
Program euromillion;
var num: array [1..5] of integer;
Procedure numbers;
var i, j: integer;
Begin
write ('Digite o número 1: ');
readln (num[1]);
for i:=2 to 5 do
for j:=1 to (i-1) do
Begin
repeat
write ('Digite o número ', i, ': ');
readln (num[i]);
until (num[i]>=1) and (num[i]<=50) and ((num[i]=num[j])=false);
End;
End;
Begin
numbers;
readln();
End.
Thanks guys :)
Although it is tempting to try and write a single block of code, as you have, it is better not to. Instead, a better way to write a program like this
is to think about splitting the task up into a number of procedures or functions
each of which only does a single part of the task.
One way to look at your task is to split it up into sub-tasks, as follows:
You prompt the user to enter a series of numbers
Once each number is entered, you check whether it is already in the array
If it isn't, you enter it in the array, otherwise prompt the user for another number
Once the array is filled, you output the numbers in the array
So, a key thing is that it would be helpful to have a function that checks whether
a new number is already in the array and returns True if it is and False otherwise. How to do that is the answer to your question.
You need to be careful about this because if you use the array a second time in the
program, you need to avoid comparing the new number with the array contents from
the previous time. I deliberately have not solved that problem in the example code below, to leave it as an exercise for the reader. Hint: One way would be to write a procedure which "clears" the array before each use of it, e.g. by filling it with numbers which are not valid lottery numbers, like negative numbers or zero. Another way would be to define a record which includes the NumberArray and a Count field which records how many numbers have been entered so far: this would avoid comparing the new number to all the elements in the
array and allow you to re-use the array by resetting the Count field to zero before calling ReadNumbers.
program LotteryNumbers;
uses crt;
type
TNumberArray = array[1..5] of Integer;
var
Numbers : TNumberArray;
Number : Integer;
function IsInArray(Number : Integer; Numbers : TNumberArray) : Boolean;
var
i : Integer;
begin
Result := False;
for i:= Low(Numbers) to High(Numbers) do begin
if Numbers[i] = Number then begin
Result := True;
break;
end;
end
end;
procedure ReadNumbers(var Numbers : TNumberArray);
var
i : Integer;
NewNumber : Integer;
OK : Boolean;
begin
// Note: This function needs to have a check added to it that the number
// the user enters is a valid lottery number, in other words that the
// number is between 1 and the highest ball number in the lottery
for i := Low(Numbers) to High(Numbers) do begin
repeat
OK := False;
writeln('enter a number');
ReadLn(NewNumber);
OK := not IsInArray(NewNumber, Numbers);
if not OK then
writeln('Sorry, you''ve already chosen ', NewNumber);
until OK;
Numbers[i] := NewNumber;
end;
end;
procedure ListNumbers(Numbers : TNumberArray);
var
i : Integer;
begin
for i := Low(Numbers) to High(Numbers) do
writeln(Numbers[i]);
end;
begin
ReadNumbers(Numbers);
ListNumbers(Numbers);
writeln('press any key');
readkey;
end.
I have a small terminal program which displays a menu. I want to have a function which takes the user's input and an array of procedure names and be able to call the procedure the user chose. I know that I could do that using if or case statements in the main program, but I want to make a unit with the above procedure and a couple of other menu functions, and if this was possible, I could make it call arbitrary procedures. Here's more or less how I would like it to work (I know it's wrong, but so you get a general idea).
program menu;
uses crt;
type procs = array [0..1] of procedure;
procedure call_procs(inp: int; procsy: procs);
begin
writeln(procsy[ord(inp)]); {And call it here.}
end;
var procsx : procs;
begin
procsx[0] := readkey; {I would like to somehow store the procedure here.}
procsx[1] := clrscr;
call_procs(0, procsx);
end.
Is there any way to do something like this? Thank you in advance.
There are a few things wrong with your original code which are not cited in your answer.
You have an array of procedure but you are calling writeln with these procedure calls as arguments as if they were function, which they are not.
readkey is a function, not a procedure, so its type doesn't match the element type of your array
Your assignment of the procedures to the array need to use # to reference the procedure pointer and not actually call the procedure
Not sure what compiler or options you're using, but int isn't the standard Pascal integer type, rather integer is.
As a niggle, since you're already using the integer index of the array, you don't need to use ord.
So the minimal changes to your code to make it basically work would be:
program menu;
uses crt;
type procs = array [0..1] of procedure;
procedure call_procs(inp: integer; procsy: procs);
begin
procsy[inp]; { call the procedure here - removed 'ord' since it's superfluous }
end;
var procsx : procs;
begin
{ procsx[0] := readkey; {- 'readkey' is a function and won't work here }
procsx[1] := #clrscr;
call_procs(1, procsx);
end.
You can create an array of functions that return char which matches the type for readkey:
program menu;
uses crt;
type procs = array [0..1] of function: char;
procedure call_procs(inp: integer; procsy: procs);
begin
writeln(procsy[inp]); { call the function; write out the returned char }
end;
function foo: char;
begin
foo := 'X';
end;
var procsx : procs;
begin
procsx[0] := #readkey;
procsx[1] := #foo;
call_procs(0, procsx);
call_procs(1, procsx);
end.
I figured out how to do this. One can use pointers to a procedure, then create an array of those pointers, and pass them to the procedure I wanted to use. Also, for some reason, it doesn't seem to work with the functions that come with Pascal (such as readkey or clrscr). For this example, one could do this:
program menu;
type
Tprocptr = procedure; {This creates a pointer to procedures.}
Tprocarray = array of Tprocptr;
procedure writeHi;
begin
writeln('Hi!');
end;
procedure writeHello;
begin
writeln('Hello!');
end;
procedure call_proc(inp: integer; procsy: Tprocarray);
{This now calls functions like one would expect.}
begin
procsy[ord(inp)];
end;
var
proclist : Tprocarray;
begin
setlength(proclist, 2);
proclist[0] := #writeHi; {The '#' creates a pointer to those procedures.}
proclist[1] := #writeHello;
call_proc(0, proclist);
end.
This works as expected, calling (in this case) the procedure writeHi, so if you run this program it will output Hi! to the terminal. If you change call_proc(0,proclist) to call_proc(1, proclist), it will call writeHello instead.
i have to do the following thing.
Make a program in Pascal that after has read a text with a list of nums., it will return the numb. of the nums that appear less than one times in the text.
The text that will be read from the program should be like that.
In the first line there are two nums. seperated by a space, n and m. N is the number of nums that exist, like if the text contains the numbers 1,2,3,4, n is 4 (1..n). M is how many lines follow. Every line has a couple of nums, a,b, (1=b) a and b are separated by a space.
The file that the program will make will have written on it a num., that says how many nyms are appeared less than two tims in the text.
All the nums. are Integer.
0=
I have finished it, but the problem is that at the new text that p has to be written, p is always 1, For me the problem is at the place that i have the bold letters, it might be because i in count and i in a arrays are different, how can i correct this???
Thank you in advance.
program MyProgr;
var
F: text;
t:Textfile;
a,count:array of Integer;
b:Integer;
i,int:Integer;
countnums:Integer;
n,m:String;
lin,nums:Integer;
Small,Big:Integer;
procedure DoWhatEver(S: string);
begin
val(s,int);
Write(s,' ');
for i:=Small to Big do
if (a[i]=int) then
count[i]:=count[i]+1;
end;
procedure FilltheArray;
begin
for i:=Small to Big do
a[i]:=i+1 ;
end;
procedure ProcessString;
var
Strng, S: string;
Last, P: integer;
begin
readln(F,Strng);
Last:=0;
while Last<length(Strng) do
begin
P:=Last+1;
while (P<=length(Strng)) and (Strng[P]<>' ') do
inc(P);
S:=copy(Strng,Last+1,(P-Last-1));
DoWhatEver(S);
Last:=P;
end
end;
procedure ProcessStringA;
var
Strng: string;
Last, P: integer;
begin
readln(F,Strng);
Last:=0;
while Last<length(Strng) do
begin
P:=Last+1;
while (P<=length(Strng)) and (Strng[P]<>' ') do
inc(P);
n:=copy(Strng,Last+1,(P-Last-1));
Val(n,nums);
Last:=P;
end
end;
procedure ProcessStringB;
var
Strng: string;
Last, P: integer;
begin
readln(F,Strng);
Last:=0;
while Last<length(Strng) do
begin
P:=Last+1;
while (P<=length(Strng)) and (Strng[P]<>' ') do
inc(P);
m:=copy(Strng,Last+1,(P-Last-1));
Val(m,lin);
Last:=P;
end
end;
begin
assign(F,'myfile.txt');
reset(F);
ProcessStringA;
Writeln(nums);
ProcessStringB;
Writeln(lin);
setlength(a,nums);
Small:=Low(a);
Big:=High(a);
for i:= Small to big do
count[i]:=0;
FillTheArray;
while not eof(F) do
ProcessString;
for i:=Small to Big do
begin
if count[i]=2 then
countnums:=countnums+1;
end;
Close(f);
Assign(t,'fileout.txt');
Rewrite(t);
Writeln(t,countnums);
close(t);
end.