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Sep 29th, 2006

Determining an Array's Length in Pascal

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I am a mainly Java and VB programmer. However, I am writing a program that generates computer code in various languages. One of these is Pascal.

What I am asking is simple.

To detemine the size of an array in Java and VB I would enter:

Pascal and Delphi Syntax (Toggle Plain Text)

 anArray.length

What is the Pascal equivalent?? I have looked arround the web and found no info. Is there no such equivalent??

Thanks for your kind help

Andrew.

Last edited by Scottie_uk; Sep 29th, 2006 at 3:03 pm.

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Scottie_uk

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Sep 30th, 2006

Re: Determining an Array's Length in Pascal

I've not used Delphi for a while but is it something like

Pascal and Delphi Syntax (Toggle Plain Text)
Length(anArray)
Length(anArray)

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Oct 8th, 2006

Re: Determining an Array's Length in Pascal

Click to Expand / Collapse Quote originally posted by Scottie_uk ...

I am a mainly Java and VB programmer. However, I am writing a program that generates computer code in various languages. One of these is Pascal.

What I am asking is simple.

To detemine the size of an array in Java and VB I would enter:
Pascal and Delphi Syntax (Toggle Plain Text)
 anArray.length
anArray.length
What is the Pascal equivalent?? I have looked arround the web and found no info. Is there no such equivalent??

Thanks for your kind help

Andrew.

Use Low() and High() to find the lowest element or highest element index, respectively, of an array.

code

Last edited by codewritinfool; Oct 8th, 2006 at 2:17 pm.

codewritinfool

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Dec 31st, 2006

Re: Determining an Array's Length in Pascal

in pascal, you have to predefine all your variable types, including array lengths, so you should already know the length.

needs_help

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Dec 31st, 2006

Re: Determining an Array's Length in Pascal

Click to Expand / Collapse Quote originally posted by needs_help ...

in pascal, you have to predefine all your variable types, including array lengths, so you should already know the length.

NOT TRUE. Free Pascal permits dynamic arrays defined like this:

Type
TByteArray : Array of Byte;
Var
A : TByteArray;

SetLength(A,1000);

After a call to SetLength, valid array indexes are 0 to 999: the array index is always zero-based.

Borland Object Pascal (Delphi) permits dynamic arrays defined like this:

var
byteArray : Array of Byte;

SetLength(byteArray, 5);

codewritinfool

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Dec 31st, 2006

Re: Determining an Array's Length in Pascal

Ok, but in dev-pascal, you can't change the length.

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Dec 31st, 2006

Re: Determining an Array's Length in Pascal

Click to Expand / Collapse Quote originally posted by needs_help ...

Ok, but in dev-pascal, you can't change the length.

dev-pascal is an IDE, not a compiler. It commonly uses Free Pascal or GNU Pascal.

I've already shown how to do it in Free Pascal.

In GNU Pascal, you can use Schemata:

http://www.mirrorservice.org/sites/w...schemademo.pas

codewritinfool

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Oct 23rd, 2011

Re: Determining an Array's Length in Pascal

it is declared at the beginning in the form:
"array name" : array["lower limit".."upper limit"] of string;
(The quotation marks are where you put in your own thing but do not put the quotation marks in the actual program.)
Eg.
Favourite_car : array[1..10] of string;

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Oct 24th, 2011

Re: Determining an Array's Length in Pascal

array lenght = size of the element type * index

You can find the size of the array in the memory as I show it above. Delphi (object pascal) has dinamic array, that we can set the length by the SetLength(array_name, element_number) procedure, so the elements starting from 0 to element_number-1. And as said, High(array_name) the upper indenx of the array, and the Low(array_name) the lowest.

FlamingClaw

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Dec 8th, 2011

Not entierly so :-)

Click to Expand / Collapse Quote originally posted by needs_help ...

in pascal, you have to predefine all your variable types, including array lengths, so you should already know the length.

For most programs we need to write, this may be true.
There are however many cases where we need to find the length of an array.

An array can be defined as open.

Pascal and Delphi Syntax (Toggle Plain Text)
VAR
  Example:ARRAY OF STRING;
  Example2:ARRAY OF ARRAY OF INTEGER;
VAR
  Example:ARRAY OF STRING;
  Example2:ARRAY OF ARRAY OF INTEGER;

These arrays are resizeable in runtime :-)

Pascal and Delphi Syntax (Toggle Plain Text)
SetLength(Example,10);
SetLength(Example2,10,10);
SetLength(Example,10);
SetLength(Example2,10,10);

A multidimensional array is nice to use this way. Each sub array can be defined separately.

Pascal and Delphi Syntax (Toggle Plain Text)
SetLength(Example2,5);
SetLength(Example2[0],10);
SetLength(Example2[1],6);
SetLength(Example2[2],90);
SetLength(Example2[3],12);
SetLength(Example2[4],19);
SetLength(Example2,5);
SetLength(Example2[0],10);
SetLength(Example2[1],6);
SetLength(Example2[2],90);
SetLength(Example2[3],12);
SetLength(Example2[4],19);

Instead of creating an array that is holding all the possible records our program can possibly need, we can design the program to only use as much memory as is actually needed on demand.

In these cases with SetLength, it makes sense to use the command HIGH(Example2[4]) in order to read out its set length.
Since SetLength always start an array at [0], the command LOW will always return Zero.

Pascal and Delphi Syntax (Toggle Plain Text)
PROCEDURE SomeParameters(CONST Params:ARRAY OF INTEGER);
  VAR
    x:BYTE;
  BEGIN
//    HIGH(Params) will return the number of integers passed in the Params array.
    FOR x:=0 TO HIGH(Params) DO BEGIN
      // Code for whatever you would like to do with the parameters.
    END;
  END;
PROCEDURE SomeParameters(CONST Params:ARRAY OF INTEGER);
  VAR
    x:BYTE;
  BEGIN
//    HIGH(Params) will return the number of integers passed in the Params array.
    FOR x:=0 TO HIGH(Params) DO BEGIN
      // Code for whatever you would like to do with the parameters.
    END;
  END;

And again... When an array is passed as parameters, to my knowledge it always start with [0], so LOW(Params) will always return Zero.

IF you however declare an array from scratch in VAR section of program.

Pascal and Delphi Syntax (Toggle Plain Text)
VAR
  Example : ARRAY[7..14];
BEGIN
  LOW(Example)// Should return 7, but we know this already as it is already defined.
END.
VAR
  Example : ARRAY[7..14];
BEGIN
  LOW(Example)// Should return 7, but we know this already as it is already defined.
END.

Best regards.

Morten Brendefu

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