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The string in Pascal is actually a sequence of characters with an optional size specification. The characters could be numeric, letters, blank, special characters or a combination of all. Extended Pascal provides numerous types of string objects depending upon the system and implementation. We will discuss more common types of strings used in programs.
You can define a string in many ways −
-
Character arrays − This is a character string which is a sequence of zero or more byte-sized characters enclosed in single quotes.
-
String variables − The variable of String type, as defined in Turbo Pascal.
-
Short strings − The variable of String type with size specification.
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Null terminated strings − The variable of pchar type.
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AnsiStrings − Ansistrings are strings that have no length limit.
Pascal provides only one string operator, string concatenation operator (+).
Examples
The following program prints first four kinds of strings. We will use AnsiStrings in the next example.
program exString;
var
greetings: string;
name: packed array [1..10] of char;
organisation: string[10];
message: pchar;
begin
greetings := ''Hello '';
message := ''Good Day!'';
writeln(''Please Enter your Name'');
readln(name);
writeln(''Please Enter the name of your Organisation'');
readln(organisation);
writeln(greetings, name, '' from '', organisation);
writeln(message);
end.
When the above code is compiled and executed, it produces the following result −
Please Enter your Name John Smith Please Enter the name of your Organisation Infotech Hello John Smith from Infotech
Following example makes use of few more functions, let”s see −
program exString;
uses sysutils;
var
str1, str2, str3 : ansistring;
str4: string;
len: integer;
begin
str1 := ''Hello '';
str2 := ''There!'';
(* copy str1 into str3 *)
str3 := str1;
writeln(''appendstr( str3, str1) : '', str3 );
(* concatenates str1 and str2 *)
appendstr( str1, str2);
writeln( ''appendstr( str1, str2) '' , str1 );
str4 := str1 + str2;
writeln(''Now str4 is: '', str4);
(* total lenghth of str4 after concatenation *)
len := byte(str4[0]);
writeln(''Length of the final string str4: '', len);
end.
When the above code is compiled and executed, it produces the following result −
appendstr( str3, str1) : Hello appendstr( str1, str2) : Hello There! Now str4 is: Hello There! There! Length of the final string str4: 18
Pascal String Functions and Procedures
Pascal supports a wide range of functions and procedures that manipulate strings. These subprograms vary implement-wise. Here, we are listing various string manipulating subprograms provided by Free Pascal −
| Sr.No. | Function & Purpose |
|---|---|
| 1 |
function AnsiCompareStr(const S1: ; const S2:):Integer; Compares two strings |
| 2 |
function AnsiCompareText(const S1: ; const S2:):Integer; Compares two strings, case insensitive |
| 3 |
function AnsiExtractQuotedStr(var Src: PChar; Quote: Char):; Removes quotes from string |
| 4 |
function AnsiLastChar(const S:):PChar; Gets last character of string |
| 5 |
function AnsiLowerCase(const s:): Converts string to all-lowercase |
| 6 |
function AnsiQuotedStr(const S: ; Quote: Char):; Quotes a string |
| 7 |
function AnsiStrComp(S1: PChar;S2: PChar):Integer; Compares strings case-sensitive |
| 8 |
function AnsiStrIComp(S1: PChar; S2: PChar):Integer; Compares strings case-insensitive |
| 9 |
function AnsiStrLComp(S1: PChar; S2: PChar; MaxLen: Cardinal):Integer; Compares L characters of strings case sensitive |
| 10 |
function AnsiStrLIComp(S1: PChar; S2: PChar; MaxLen: Cardinal):Integer; Compares L characters of strings case insensitive |
| 11 |
function AnsiStrLastChar(Str: PChar):PChar; Gets last character of string |
| 12 |
function AnsiStrLower(Str: PChar):PChar; Converts string to all-lowercase |
| 13 |
function AnsiStrUpper(Str: PChar):PChar; Converts string to all-uppercase |
| 14 |
function AnsiUpperCase(const s:):; Converts string to all-uppercase |
| 15 |
procedure AppendStr(var Dest: ; const S:); Appends 2 strings |
| 16 |
procedure AssignStr(var P: PString; const S:); Assigns value of strings on heap |
| 17 |
function CompareStr(const S1: ; const S2:):Integer; overload; Compares two strings case sensitive |
| 18 |
function CompareText(const S1: ; const S2:):Integer; Compares two strings case insensitive |
| 19 |
procedure DisposeStr(S: PString); overload;
Removes string from heap |
| 20 |
procedure DisposeStr(S: PShortString); overload; Removes string from heap |
| 21 |
function IsValidIdent( const Ident:):Boolean; Is string a valid pascal identifier |
| 22 |
function LastDelimiter(const Delimiters: ; const S:):Integer; Last occurrence of character in a string |
| 23 |
function LeftStr(const S: ; Count: Integer):; Gets first N characters of a string |
| 24 |
function LoadStr(Ident: Integer):; Loads string from resources |
| 25 |
function LowerCase(const s: ):; overload; Converts string to all-lowercase |
| 26 |
function LowerCase(const V: variant ):; overload; Converts string to all-lowercase |
| 27 |
function NewStr(const S:):PString; overload; Allocates new string on heap |
| 28 |
function RightStr(const S: ; Count: Integer):; Gets last N characters of a string |
| 29 |
function StrAlloc(Size: Cardinal):PChar; Allocates memory for string |
| 30 |
function StrBufSize(Str: PChar):SizeUInt; Reserves memory for a string |
| 31 |
procedure StrDispose(Str: PChar); Removes string from heap |
| 32 |
function StrPas(Str: PChar):; Converts PChar to pascal string |
| 33 |
function StrPCopy(Dest: PChar; Source:):PChar; Copies pascal string |
| 34 |
function StrPLCopy(Dest: PChar; Source: ; MaxLen: SizeUInt):PChar; Copies N bytes of pascal string |
| 35 |
function UpperCase(const s:):; Converts string to all-uppercase |
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