These notes are a supplement to the documentation for M version 05/31/91
and will be included in the documentation of a later release.  The news help
topic now contains information related to M updates and bug fixes.

Indexed Variables
-----------------
Only variables can be indexed (in C, expressions can be indexed too).
Indexed variables can only be used in expressions and basic assignments,
such as A(:,1:2) = expr.  ++ and -- can not be applied to an indexed variable.
++x(1);  x(2:3) += 4;  are not allowed.  They should be.
Also,  y = x(2:3) = [ 1 2];  produces y = x, not y=[1 2].

Input Line Buffering
--------------------
Since M buffers input lines in a circular queue of 60 lines with up to 128
characters per line, this means (1) if a function definition exceeds 60 lines,
the source code will not be saved properly for listing via the `list' and
`save' commands; (2) input lines containing numbers should not exceed 128
characters, since a number may get split across two input line buffers and
will not be converted properly by sscanf() in M.

Except within numeric constants, a backslash as the last character in a line
causes the following newline to be ignored.  This is most useful for specifying
long row vectors without exceeding the 128 character limit discussed above.

If the first character of a line is $ then M uses the remainder of the line
as an argument to system() to execute a sub-shell.

If the first character of a line is ! then M executes a history substitution
siniliar to that in the Unix csh.  Lines may be recalled by specifying
their number as shown by `history' or by their starting string of characters.

Eventually, more features of the Unix csh command recall and editing may be
added to M.

Control-C
---------
Control-C interrupts M and restarts the parser.  Depending on what was being
executed, the workspace may be corrupted, so control-C should be used only
in emergencies.

Syntax Errors
-------------
Most syntax errors produce the informative message `syntax error'.  As the
parser tries to recover from the error, if you don't receive the m> prompt
after pressing Return, try entering `;' or `}' or control-C if all else
fails.  Error reporting and recovery may be improved in a later version.