string to integer conversion in Pascal, How to do it?

Question

How to convert a number printed in a string into integer?

Thank you.

President James K. Polk · Accepted Answer · 2025-05-12 16:32:38Z

11

This is the procedure Val:

procedure Val(S; var V; var Code: Integer);

This procedure operates on integer and real numbers.

Parameters:

S char sequence; for proper conversion, it has to contain only characters from the set +-,.0123456789.
V The result of conversion, if conversion succeeds. If the result is going to be an Integer, then S can't contain , or ..
Code Returns the position in S of the character that interrupted the conversion, if conversion does not succeed.

Use cases:

Var Value :Integer;

Val('1234', Value, Code);  // Value = 1234, Code = 0
Val('1.234', Value, Code); // Value = 0, Code = 2
Val('abcd', Value, Code);  // Value = 0, Code = 1

edited May 12 at 16:32

President James K. Polk

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answered Nov 5, 2010 at 10:37

Damian Leszczyński - Vash

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Comments

Mazhar Karimi · Accepted Answer · 2010-11-05 10:37:42Z

1

 Textval := '123';
    Val(Textval, Number, Code)  ---> Code = 0, Number = 123

   Textval := '12345x2';
   Val( Textval, Number, Code)  ---> Code = 6,  Number remains unchanged;

Val( TextVal, Number , Code) which converts String to a number. if possible the result of code = 0, elese error indication number.

answered Nov 5, 2010 at 10:37

Mazhar Karimi

Comments

Kai Burghardt · Accepted Answer · 2024-07-05 16:28:20Z

Since ISO standard 10206 “Extended Pascal” the procedure readStr is built‑in into the programming language. It is equivalent in function to read/readLn in conjunction with a text file (except that no text file is needed). That means leading blanks are ignored, followed by one valid integer literal which is terminated by blanks or simply the end of string. Example:

program readStrDemo(output);
    var
        n: integer;
    begin
        readStr('  +1234 Hello world!', n);
        writeLn(n) { prints 1234 }
    end.

In contrast to Borland Pascal’s val procedure you cannot emit a user‑friendly error message, though, specifically which (first) character is causing troubles. Pascal’s built‑in read, readLn and readStr procedures simply fail, the specifics are processor‐dependent. On the other hand, read, readLn and readStr are standardized so there is no vendor lock‑in.

Note, in addition to reading decimal integer literals, read/readLn/readStr can parse any integer literal that is legal in your Pascal source code, including base‑prefixed integer literals such 16#FF (255).

pyCoder · Accepted Answer · 2010-11-05 10:36:22Z

0

You can use Val function.

Example:

var
   sNum: String;
   iNum: Integer;
   code: Integer;

begin
   s := '101';
   Val(s, iNum, code); 
end.

answered Nov 5, 2010 at 10:36

pyCoder

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1 Comment

Luis Over a year ago

This code don't work. The s must be sNum

Peternak Kode Channel · Accepted Answer · 2014-10-13 08:36:02Z

0

You can use like this,

var

i: integer;
s: string;
begin
str(i, s);
write(i);

edited Oct 13, 2014 at 8:36

answered Oct 13, 2014 at 8:16

Peternak Kode Channel

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1 Comment

Kai Burghardt Over a year ago

−1 This is the wrong way around. The question wants string → integer. However, Borland Pascal’s str procedure turns numeric (and enumerated type) values into a string.

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