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1995-07-17
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Needed enhancements
Send calc comments, suggestions, bug fixes, enhancements and
interesting calc scripts that you would like you see included in
future distributions to:
dbell@canb.auug.org.au
chongo@toad.com
The following items are in the calc wish list. Programs like this
can be extended and improved forever.
* Implement an autoload feature. Associate a calc library filename
with a function or global variable. On the first reference of
such item, perform an automatic load of that file.
* Use faster multiply and divide algorithms for large numbers.
* Add error handling statements, so that QUITs, errors from the
'eval' function, division by zeroes, and so on can be caught.
This should be done using syntax similar to:
ONERROR statement DO statement;
Something like signal isn't versatile enough.
* Add a debugging capability so that functions can be single stepped,
breakpoints inserted, variables displayed, and so on.
* Figure out how to write all variables out to a file, including
deeply nested arrays, lists, and objects.
* Implement pointers.
* Eliminate the need for the define keyword by doing smarter parsing.
* Allow results of a command (or all commands) to be re-directed to a
file or piped into a command.
* Add some kind of #include and #define facility. Perhaps use
the C pre-processor itself?
* Allow one to undefine anything. Allow one to test if anything
is defined.
* Support a more general input and output base mode other than
just dec, hex or octal.
* Allow support of POSIX bc via a translator reads bc commands,
converts it to calc and pipes it into calc.
* Implement a form of symbolic algebra. Work on this has already
begun. This will use backquotes to define expressions, and new
functions will be able to act on expressions. For example:
x = `hello * strlen(mom)`;
x = sub(x, `hello`, `hello + 1`);
x = sub(x, `hello`, 10, `mom`, "curds");
eval(x);
prints 55.
* Place the results of previous commands into a parallel history list.
Add a binding that returns the saved result of the command so
that one does not need to re-execute a previous command simply
to obtain its value.
If you have a command that takes a very long time to execute,
it would be nice if you could get at its result without having
to spend the time to reexecute it.
* Add a binding to delete a value from the history list.
One may need to remove a large value from the history list if
it is very large. Deleting the value would replace the history
entry with a null value.
* Add a binding to delete a command from the history list.
Since you can delete values, you might as well be able to
delete commands.
* All one to alter the size of the history list thru config().
In some cases, 256 values is too small, in others it is too large.
* Add a builtin that returns a value from the history list.
As an example:
histval(-10)
returns the 10th value on the history value list, if such
a value is in the history list (null otherwise). And:
histval(23)
return the value of the 23rd command given to calc, if
such a value is in the history list (null otherwise).
It would be very helpful to use the history values in
subsequent equations.
* Add a builtin that returns command as a string from the
history list. As an example:
history(-10)
returns a string containing the 10th command on the
history list, if a such a value is in the history list
(empty string otherwise). And:
history(23)
return the string containing the 23rd command given to calc, if
such a value is in the history list (empty string otherwise).
One could use the eval() function to re-evaluate the command.
* Restore the command number to calc prompts. When going back
in the history list, indicate the command number that is
being examined.
The command number was a useful item. When one is scanning the
history list, knowing where you are is hard without it. It can
get confusing when the history list wraps or when you use
search bindings. Command numbers would be useful in
conjunction with positive args for the history() and histval()
functions as suggested above.
* Add a builtin that returns the current command number.
For example:
cmdnum()
returns the current command number.
This would allow one to tag a value in the history list. One
could save the result of cmdnum() in a variable and later use
it as an arg to the histval() or history() functions.
* Add a builtin to determine if an object as been defined.
For example:
isobjdef("surd")
would return true if one had previously defined the
surd object. I.e., if "obj surd {...};" had been
executed.
One cannot redefine an object. If a script defines an object,
one cannot reload it without getting lots of already defined
errors. If two scripts needed the same object, both could
define it and use isobjdef() to avoid redefinition problems.
* Add a builtin to determine if a function as been defined.
For example:
isfunct("foo")
would return true if foo has been defined as a function.
* Permit one to destroy an object.
What if one does want to redefine an object? Consider the case
where one it debugging a script and wants to reload it. If
that script defines an object you are doomed. Perhaps
destroying a object would undefine all of its related functions
and values?
* Port calc to a 64 bit machine, or a machine where long was larger
than an int.
There are at least two issues here. The first is fix places
where calc assumes that an int and a long are the same size.
The second and more important would be to change calc so that
it could be configured to work with a base of 2^32. (Right now
calc is somewhat wired to use base 2^16).
In other words first make calc 64 bit safe, then increase
performance on 64 bit machines by allowing one to configure
(via the Makefile) calc to use an larger internal base.
* One some machines (such as the 486), floating point can be faster
than integer arithmetic. Often such floating point would allow
for a larger base than 2^16, allowing calc to run even faster.
Allow calc to take advantage of such hardware.
* Add NAN's (Not A Number's) to calc. Where is it reasonable, change
calc to process these values in way similar to that of the IEEE
floating point.
* Add a factoring builtin functions. Provide functions that perform
multiple polynomial quadratic sieves, elliptic curve, difference
of two squares, N-1 factoring as so on. Provide a easy general
factoring builtin (say factor(foo)) that would attempt to apply
whatever process was needed based on the value.
Factoring builtins would return a matrix of factors.
It would be handy to configure, via config(), the maximum time
that one should try to factor a number. By default the time
should be infinite. If one set the time limit to a finite
value and the time limit was exceeded, the factoring builtin
would return whatever if had found thus far, even if no new
factors had been found.
Another factoring configuration interface, via config(), that
is needed would be to direct the factoring builtins to return
as soon as a factor was found.
* Allow one to disable, via config, the printing of the leading ~
on truncated numeric values.
Sometimes the leading ~'s are more annoying than helpful.
* Allow one to disable, via config, the printing of the leading tab
when printing the value of a command that one just typed.
Most of the time, the leading tab is reasonable. Sometimes
it is not. It would be helpful if one could turn off the
tab in such cases.
* Allow one to config calc break up long output lines.
The command: calc '2^100000' will produce one very long
line. Many times this is reasonable. Long output lines
are a problem for some utilities. It would be nice if one
could configure, via config(), calc to fold long lines.
By default, calc should continue to produce long lines.
One option to config should be to specify the length to
fold output. Another option should be to append a trailing
\ on folded lines (as some symbolic packages use).
* Add scanf() and fscanf() functions.
The scanf function should be able to handle both long lines
and split lines with trailing \'s. It should also be able
to ignore the leading ~.