math::constants(n) Tcl Math Library math::constants(n)______________________________________________________________________________NAME
math::constants - Mathematical and numerical constantsSYNOPSIS
package require Tcl ?8.3?
package require math::constants ?1.0.1?
::math::constants::constants args
::math::constants::print-constants args
_________________________________________________________________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:
· One for importing the constants
· One for reporting which constants are defined and what values
they actually have.
The motivation for this package is that quite often, with (mathemati‐
cal) 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:
· You need to remember the proper formula or value and that is
error-prone.
· Especially with the use of mathematical functions like atan you
assume that they have been accurately implemented. This is sel‐
dom 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:
· basic constants like pi, e, gamma (Euler's constant)
· derived values like ln(10) and sqrt(2)
· purely numerical values such as 1/3 that are included for conve‐
nience and for the fact that certain seemingly trivial computa‐
tions like:
set value [expr {3.0*$onethird}]
give exactly the value you expect (if IEEE arithmetic is avail‐
able).
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://source‐
forge.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
CATEGORY
Mathematics
COPYRIGHT
Copyright (c) 2004 Arjen Markus <arjenmarkus@users.sourceforge.net>
math 1.0.1 math::constants(n)
