midS2 - replace middle portion of string
midS2(s, t, n, m, flag)
struct string *s, *t;
short n, m;
MidS2 replaces the portion of the string pointed to by s
beginning at location n with the string pointed to by t.
The copy is performed in place, i.e., without re-allocating or
moving the text buffer of the target string. Locations are numbered
starting with one. If flag is set, the replacement consists
the entire source string. Otherwise the replacement is limited to
m characters. In any of these cases, if the replacement would
extend beyond the end of the target string, the replacement is further
limited to avoid this condition. These cases are not errors.
This function implements the MID$ statement.
Error 5 (Illegal function call) is generated if n is non-positive
or if flag is set and m is negative or if location n
lies beyond the end of the target string. The target string is not altered.
The Basmark QuickBASIC Programmerís Manual