[metapost] Re: a "randomseed" workaround
laurent at math.toronto.edu
Mon Mar 7 07:40:17 CET 2005
Karl and others!
Some quick reactions:
KB> Taco, if it's allowed to be system-dependent, then how
> about using /dev/random on systems that support it? That
> would be much, much, more random than just using the
> current time. (There might be better things than
> /dev/random these days, for that matter; a lot of work has
> gone into this topic, since ssh and other crypto
> applications need randomness.)
A good comment to go into web files for implementors.
LS> It would be helpful to add to mp documentation a fairly complete
> table of primitives that are common to mf and mp.
KS> No question. It would also be helpful to write a
KS> completely new MP manual...
Such a table is not just desirable but a *reasonable* task
for a fledging mp expert. I would hope many programmers
reading this are more competent than I am or Karl.
I expect Hobby and confirmed experts like Jacko would
check it out.
Incidentally, such a table could be readily enhanced for mf users.
KB> The current doc is available from sarovar (Larry, you
> asked me about this separately). You can get it through
> CVS (http://sarovar.org/projects/metapost/), or directly
> from the web:
If you were to maintain a current ".pdf" beta version of the
mp documentation, listmembers would provide a max of
comments/corrections with a min of effort.
LS> It took me quite a while to locate the conversion
> from string to numeric by "scantokens" (see below).
KB> I'm not sure what I'm supposed to see below?
> Sorry, I guess I don't know mp well enough
> to extract the meaning here.
I was referring to the line:
seed_adjuvant:= scantokens(str); %% (*)
where str is a string (in fact a decimal represented integer)
that arose as
"scantokens" is a strange syntax for a type conversion.
It's a more general low level operation for mf and etex.
"decimal" converts back from numeric to string.
LS> %% Default for metafont is (in effect)
> %% randomseed:= day + time*epsilon
I was more-or-less quoting the mf book, qv.
> This in itself is a useful thing to put in the manual,
> so I'll do that.
Except that time is in minutes, whence misbehavior of randomseed.
Seems more suitable for web source.
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