18.104.22.168 Deviations from Standard Modula-2
A few changes have been made to make Modula-2 programs easier to debug.
This is done primarily via loosening its type strictness:
- Unlike in standard Modula-2, pointer constants can be formed by
integers. This allows you to modify pointer variables during
debugging. (In standard Modula-2, the actual address contained in a
pointer variable is hidden from you; it can only be modified
through direct assignment to another pointer variable or expression that
returned a pointer.)
- C escape sequences can be used in strings and characters to represent
non-printable characters. GDB prints out strings with these
escape sequences embedded. Single non-printable characters are
printed using the ‘CHR(nnn)’ format.
- The assignment operator (
:=) returns the value of its right-hand
- All built-in procedures both modify and return their argument.