How could i multiply a string by a number to achieve n amount of repetitions of that string in a Labels caption, i.e
if n = 5 then 's'*n= 'sssss' which would then become the labels caption.
anything along those lines returns the error that the operator is not applicable to the operand type.
thanks
There's no built in operator that does what you want. Your code would work in Python, but not in Delphi.
If your string is a single character then you can use StringOfChar:
Caption := StringOfChar('s', n);
For a longer input string use DupeString from the StrUtils unit:
Caption := DupeString('blah', n);
Delphi does not allow that syntax. However, there is a function called DupeString, in StrUtils.pas that amounts to the same thing:
Label1.Caption := DupeString('test', 4);
Related
procedure TForm1.Button1Click(Sender: TObject);
var
term1: integer;
term2: integer;
term3: integer;
j: integer;
begin
term1 := (0);
term2 := (1);
for j := 1 to 100 do;
begin
term3 :=( term1 + term2);
Memo1.Text:=inttostr(term3);
term1 := term2;
term2 := term3;
end;
end;
end.
This is what I have so far, but term1 and term2 don't want to add up. I have tried some different things, but for some reason the integers never want to add up.
There are several problems with your code
The semicolon after for j := 1 to 100 do prevents your next code that is withing begin..end block to be run in a loop. Why? The code that is to be run in each cycle of for loop is the one that follows the do until the first semicolon. Since you put semicolon just after the do this basically means that empty block of code is ran in a loop. Your begin..end block comes after that. Removing the semicolon after do will fix that.
You are using Memo1.Text:=inttostr(term3); to write the result into Memo. The problem with this is that this will rewrite entire text of the Memo every time so you will end up with only one line showing the last number. You should use Memo1.Lines.Add(inttostr(term3)); instead so that new line is added each time.
Lastly you are using Integer type for your variables. Since numbers in Fibonacci sequence grows very fast you will quickly exceed the maximum value that can be stored in Integer which in Delphi is Signed 32 bit Integer with a max value of 2147483647. You will have to use bigger integer types like 64 bit Integer type and since you are only dealing with positive numbers you should therefore use Unsigned 64 bit Integer that in declared in Delphi by UInt64 type. You can read more about Delphi default Integer types in documentation. Unfortunately not even UInt64 will is big enough for value of all first 100 numbers of Fibonacci sequence. So you will have to use one of the BigIntegers libraries for Delphi to do this properly. There are several of them available on internet.
You have an erroneous ; on your loop that you need to remove:
for j := 1 to 100 do;
^
I need to print values that are in a matrix, these may vary from integer to real. As an example a matrix that my program use, named kernel, is shown below:
kernel[0,0]:= 1/16;
kernel[0,1]:= 2/16;
kernel[0,2]:= 1/16;
kernel[1,0]:= 2/16;
kernel[1,1]:= 4/16;
kernel[1,2]:= 2/16;
kernel[2,0]:= 1/16;
kernel[2,1]:= 2/16;
kernel[2,2]:= 1/16;
the issue comes when printing each of them, because I couldn't find a way to print a number like 1/16 in a easy-to-read way, the program displays something like 6.2500000000000000000000000000E-2 which is OK but I would prefer to have something more aesthetic like 0.0625 or even better 1/16. Does anyone acknowledge a way of formatting that allows me to do so?
Each array element holds the value of the fraction.
To write the value as a fraction you can simply calculate the numerator as the product of the array element and the denominator.
I prefer to use the Format() function for display formatting.
Given the array you show, two index variables, a and b and the denominator
denominator := 16;
for a := 0 to 2 do
for b := 0 to 2 do
begin
s := format('kernel[%d,%d] = %d/%d',[a,b,round(kernel[a,b]*denominator),denominator]);
memo1.Lines.Add(s);
end;
Write a program to convert an integer number to its hexadecimal representation without using inbuilt functions.
Here is my code, but it is not working. Can anyone tell where is the mistake?
It is giving an error:
"Project raised exception class EAccessViolation with message 'Access violation at address 00453B7B in module 'Project.exe'.Write of address FFFFFFFF'.Process stopped.Use Step or Run to continue."
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls,Forms,
Dialogs;
type
TForm1 = class(TForm)
end;
function hexvalue(num:Integer):Char;
var
Form1: TForm1;
implementation
{$R *.dfm}
function hexvalue(num:Integer):Char;
begin
case num of
10: Result:='A';
11: Result:='B';
12: Result:='C';
13: Result:='D';
14: Result:='E';
15: Result:='F';
else Result:=Chr(num);
end;
end;
var
intnumber,hexnumber,actualhex:String;
integernum:Integer;
i,j,k:Byte;
begin
InputQuery ('Integer Number','Enter the integer number', intnumber);
integernum:=StrToInt(intnumber);
i:=0;
while integernum >= 16 do
begin
hexnumber[i]:=hexvalue(integernum mod 16);
integernum:= integernum div 16;
Inc(i);
end;
hexnumber[i]:= hexvalue(integernum);
k:=i;
for j:=0 to k do
begin
actualhex[j]:= hexnumber[i];
Dec(i);
end;
ShowMessage(actualhex);
end.
Since this obviously is a homework assignment, I don't want to spoil it for you and write the solution, but rather attempt to guide you to the solution.
User input
In real code you would need to be prepared for any mistake from the user and check that the input really is integer numbers only and politely ask the user to correct the input if erroneous.
Conversion loop
You have got that OK, using mod 16 for each nibble of integernum and div 16 to move to the next nibble, going from units towards higher order values.
Conversion of nibble to hex character
Here you go wrong. If you would have written out also the cases for 0..9, you could have got the case statement right. As others have commented, Chr() takes an ASCII code. However, using a case statement for such a simple conversion is tedious to write and not very efficient.
What if you would have a lookup table (array) where the index (0..15) directly would give you the corresponding hex character. That would be much simpler. Something like
const
HexChars: array[_.._] of Char = ('0',_____'F')
I leave it to you to fill in the missing parts.
Forming the result (hex string)
Your second major mistake and the reason for the AV is that you did not set the length of the string hexnumber before attempting to acess the character positions. Another design flaw is that you fill in hexnumber backwards. As a result you then need an extra loop where you reverse the order to the correct one.
There are at least two solutions to solve both problems:
Since you take 32 bit integer type input, the hex representation is not more than 8 characters. Thus you can preset the length of the string to 8 and fill it in from the lower order position using 8 - i as index. As a final step you can trim the string if you like.
Don't preset the length and just concatenate as you go in the loop hexnumber := HexChars[integernum mod 16] + hexnumber;.
Negative values
You did not in any way consider the possibility of negative values in your code, so I assume it wasn't part of the task.
First mistake : String are 1 indexed. Meaning that the index of their first character is 1 and not 0. You initialize "i" to 0 and then try to set hexnumber[i].
Second mistake : Strings might be dynamic, but they don't grow automatically. If you try to access the first character of an empty string, it won't work. You need to call SetLength(HeXNumber, NumberOfDigits). You can calculate the number of digits this way :
NumberOfDigits := Trunc(Log16(integernum)) + 1;
Since Log16 isn't really something that exists, you can either use LogN(16,integernum) or (Log(IntegerNum) / Log(16)) depending on what is available in your version of Delphi.
Note that this might return an invalid value for very, very large value (high INT64 range) due to rounding errors.
If you don't want to go that road, you could replace the instruction by
hexnumber := hexvalue(integernum mod 16) + hexnumber;
which would also remove the need to invert the string at the end.
Third Mistake : Using unsigned integer for loop variable. While this is debatable, the instruction
for I := 0 to Count - 1 do
is common practice in Delphi without checking Count > 0. When count = 0 and using an unsigned loop counter, you'll either get an integer overflow (if you have them activated in your project options) or you'll loop High(I) times, which isn't what you want to be doing.
Fourth mistake : already mentionned : Result:=Chr(num) should be replaced by something like Result := InttoStr(Num)[1].
Personally, I'd implement the function using an array.
HexArr : Array[0..15] of char = ('0', '1',...,'D','E','F');
begin
if InRange(Num, 0, 15) then
Result := HexArr[Num]
else
//whatever you want
end;
procedure TForm1.Button1Click(Sender: TObject);
var
xlap,xlbook,xlsheet:variant;
y:integer;
begin
xlap:=createoleobject('excel.application');
xlbook:=xlap.workbooks.add;
xlap.visible:=true;
xlsheet:=xlbook.worksheets.add;
for y:=1 to 50 do
begin
xlsheet.cells[y,2].value:= concat('=IF(A',y,'>6,"Good","Bad")')
inc(y);
end;
end;
That's my code to make an Excel through Delphi. I want to input the IF formula into column B of the Excel, but there is error when I use the concat('=IF(A',y,'>6,"Good","Bad")').
May be I need another way to include y between those strings.
Any suggestion? Thanks before
Delphi has a format statement bit like sprintf printf in c, well nearly
xlsheet.cells[y,2].value:= format('=IF(A%d>6,"Good", "Bad")',[y])
%d is a place holder for an int. Look it up for loads of other stuff.
NB the variables you want to interpolate are assed in an array.
In addition to Tony's answer about Format, here are a couple of other approaches. (Format is great if you have mixed types or many values, but it carries some overhead that might not be needed.)
You can concatenate strings with a simple + - in fact, the Concat documentation says it does the same thing but is faster:
Temp := 'ing';
Str := 'Test' + Temp; // Str = 'Testing'
As your y variable is an integer, you'll need to convert it to a string first (note you don't need to Inc(y);, as the loop will do that already - it's automatically incremented from the starting value to the ending value on each pass through the loop):
for y:=1 to 50 do
begin
xlsheet.cells[y,2].value:= '=IF(A' + IntToStr(y) + '>6,"Good","Bad")';
end;
I'm working with Delphi 2009,I binged my question,but the answers I've gotten are outdated since It doesn't recognise StrtoFloat in Delphi2009.
I'm asking how to convert an integer ,for example, '1900000' to '1,900,000'?
You can also use the format command. Because the format expects a real number, adding 0.0 to the integer effectively turns it into an extended type.
Result := Format('%.0m',[intValue + 0.0]));
This handles negative numbers properly and adds the currency symbol for the users locale. If the currency symbol is not wanted, then set CurrencyString := ''; before the call, and restore it afterwards.
SavedCurrency := CurrencyString;
try
CurrencyString := '';
Result := Format('%.0m',[intValue + 0.0]));
finally
CurrencyString := SavedCurrency;
end;
To force commas, just set the ThousandSeparator := ',';
CurrencyString := '!';
ThousandSeparator := '*';
Result := Format('%.0m',[-1900000.0]);
// Returns (!1*900*000) in my locale.
The "period" in the mask determines how the fractional portion of the float will display. Since I passed 0 afterwards, it is telling the format command to not include any fractional pieces. a format command of Format('%.3m',[4.0]) would return $4.000.
I currently use this :
function FloatToCurrency(const f: double): string;
begin
Result := FormatFloat('#,###.##;1;0', f);
end;
It doesn't work with negative numbers, but since you need currency you won't have that problem.
You can assign Integer to Currency directly by assignment, the compiler will do the conversion for you:
var
Int : Integer;
Cur : Currency;
begin
Int := 1900000;
Cur := Int;
ShowMessage(CurrToStr(Cur)); // 1900000
ShowMessage(Format('%m', [Cur]); // 1,900,000.00 in US/UK/NZ/AU etc, "1 900 000,00" in Spain etc.
ShowMessage(Format('%.0m', [Cur]); // 1,900,000 in US/UK/NZ/AU etc, "1 900 000" in Spain etc.
end;
If you want Commas using Spanish regional settings set ThousandSeparator := ','; or use the extended CurrToStrF(amount, ffCurrency, decimals, FormatSettings)) version.
The verison with FormatSettings is also thread-safe.
Note: You can't assign Currency to Integer directly, You would need to use Int := Trunc(Cur) but this is inefficient as it converts to float first (unless compiler does something smart).
wouldnt this be more of a format thing, delphi should have some type of support for formating the number into a string the way you want right? Besides isnt the newer versions of delphi more aligned with the .net framework?