math::constants(n)						 Tcl Math Library						math::constants(n)

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NAME

       math::constants - Mathematical and numerical constants

SYNOPSIS

       package require Tcl  ?8.3?

       package require math::constants	?1.0.1?

       ::math::constants::constants args

       ::math::constants::print-constants args

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DESCRIPTION

       This  package defines some common mathematical and numerical constants.	By using the package you get consistent values for numbers like pi
       and ln(10).

       It defines two commands:

       o      One for importing the constants

       o      One for reporting which constants are defined and what values they actually have.

       The motivation for this package is that quite often, with (mathematical) computations, you need a good approximation to, say, the ratio	of
       degrees to radians. You can, of course, define this like:

	   variable radtodeg [expr {180.0/(4.0*atan(1.0))}]

       and use the variable radtodeg whenever you need the conversion.

       This has two drawbacks:

       o      You need to remember the proper formula or value and that is error-prone.

       o      Especially with the use of mathematical functions like atan you assume that they have been accurately implemented. This is seldom or
	      never the case and for each platform you can get subtle differences.

       Here is the way you can do it with the math::constants package:

	   package require math::constants
	   ::math::constants::constants radtodeg degtorad

       which creates two variables, radtodeg and (its reciprocal) degtorad in the calling namespace.

       Constants that have been defined (their values are mostly taken from mathematical tables with more precision than usually can  be  handled)
       include:

       o      basic constants like pi, e, gamma (Euler's constant)

       o      derived values like ln(10) and sqrt(2)

       o      purely  numerical  values such as 1/3 that are included for convenience and for the fact that certain seemingly trivial computations
	      like:

		  set value [expr {3.0*$onethird}]

	      give exactly the value you expect (if IEEE arithmetic is available).

PROCEDURES

       The package defines the following public procedures:

       ::math::constants::constants args
	      Import the constants whose names are given as arguments

       ::math::constants::print-constants args
	      Print the constants whose names are given as arguments on the screen (name, value and description) or, if no  arguments  are  given,
	      print all defined constants. This is mainly a convenience procedure.

BUGS, IDEAS, FEEDBACK
       This  document, and the package it describes, will undoubtedly contain bugs and other problems.	Please report such in the category math ::
       constants of the Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883].  Please also report any ideas  for  enhancements  you
       may have for either package and/or documentation.

KEYWORDS

       constants, degrees, e, math, pi, radians

COPYRIGHT

       Copyright (c) 2004 Arjen Markus <arjenmarkus@users.sourceforge.net>

math								       1.0.1							math::constants(n)