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PROCEDURE Replace (VAR s: ARRAY OF CHAR; pos, len: INTEGER; IN rep: ARRAY OF CHAR)
Replaces the stretch [pos, MIN(pos+len, Len(s))) in s with the string in rep. The characters after the replaced stretch are moved if necessary. The result is truncated if s is not large enough.
Hint: if len = 0 then rep is inserted in s at position pos. If LEN(rep$) = 0 then the stretch [pos, MIN(pos+len, LEN(s$))) is deleted from s.

Pre
len >= 0 20
pos >= 0 21
Valid(s) & Valid(rep) (not checked)

Post
Valid(s)

VAR a: ARRAY 5 OF CHAR;
ERROR 1:
    a := "ABCD";
    Strings.Replace(a, 1, 1, "xy");
    StdLog.String(a); <-- index out of range
ERROR 2:
    a := "ABCD";
    Strings.Replace(a, 1, 0, "x");
    StdLog.String(a); <-- index out of range

PROCEDURE Replace* (VAR s: ARRAY OF CHAR; pos, len: INTEGER; IN rep: ARRAY OF CHAR);
...
        ELSE (* insert the remaining part of rep *)
            len := LEN(rep$) - j; k := lenS + len;
            IF k > max THEN k := max END;
            s[k] := 0X; DEC(k); <--- DEC(k) is added
            WHILE k - len >= i DO s[k] := s[k-len]; DEC(k) END;
            WHILE (rep[j] # 0X) & (i < max) DO s[i] := rep[j]; INC(i); INC(j) END
        END
    END
END Replace;

Hello Manuel,

I agree with you. Neither the specification nor the intention of the source code corresponds to this behaviour. And I think that your correction is good too.

It's strange to think that this bug was never noticed before in a so often used procedure!

Regards.

Gérard