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6.10.2 String Operations

In the following description, s1 and s2 may be arbitrary string expressions, s is a variable of string type.

WriteStr (s, write-parameter-list)
ReadStr (s1, read-parameter-list)
Write to a string and read from a string. The parameter lists are identical to Write/Read from Text files. The semantics is closely modeled after file I/O.
Index (s1, s2)
If s2 is empty, return 1 else if s1 is empty return 0 else returns the position of s2 in s1 (an integer).
Length (s1)
Return the length of s1 (an integer from 0 .. s1.Capacity).
Trim (s1)
Returns a new string with spaces stripped of the end of s.
SubStr (s1, i)
SubStr (s1, i, j)
Return a new substring of s1 that contains j characters starting from i. If j is missing, return all the characters starting from i.
EQ (s1, s2)
NE (s1, s2)
LT (s1, s2)
LE (s1, s2)
GT (s1, s2)
GE (s1, s2)
Lexicographic comparisons of s1 and s2. Returns a boolean result. Strings are not padded with spaces.
s1 = s2
s1 <> s2
s1 < s2
s1 <= s2
s1 > s2
s1 >= s2
Lexicographic comparisons of s1 and s2. Returns a boolean result. The shorter string is blank padded to length of the longer one, but only in --extended-pascal mode.

GPC supports string catenation with the + operator or the Concat function. All string-types are compatible, so you may catenate any chars, fixed length strings and variable length strings.

     program ConcatDemo (Input, Output);
       Ch  : Char;
       Str : String (100);
       Str2: String (50);
       FStr: packed array [1 .. 20] of Char;
        Ch := '$';
        FStr := 'demo';  { padded with blanks }
        Write ('Give me some chars to play with: ');
        ReadLn (Str);
        Str := '^' + 'prefix:' + Str + ':suffix:' + FStr + Ch;
        WriteLn (Concat ('Le', 'ng', 'th'), ' = ', Length (Str));
        WriteLn (Str)

Note: The length of strings in GPC is limited only by the range of Integer (at least 32 bits, i.e., 2 GB, on most platforms), or the available memory, whichever is smaller).

When trying to write programs portable to other EP compilers, it is however safe to assume a limit of about 32 KB. At least Prospero's Extended Pascal compiler limits strings to 32760 bytes. DEC Pascal limits strings to 65535 bytes.