Sarnold Acronym for Multiple Precision Arithmetics. Library in pure Tcl available at : http://sarnold.free.fr/
Released with a BSDish License. The fact is that the floating-point numbers are still experimental, even if it 'works'. (that means, the precision of fp. numbers is a subject i personnaly do not master) I guess it is not obvious to do such computations without losing precision at each step.
What's new : in tcllib there is a bignum implementation that is much faster than mine. For your information it uses lists as an internal representation of bignums.
Examples
with a 333MHz PII 100MHz PCI Bus PC with Windows Me.
(mpa-v0.11) 50 % package require mpa
0.11
(mpa-v0.11) 51 % mpa::int::add 111111111111111111111 98237827463784678346478
98348938574895789457589
(mpa-v0.11) 52 % mpa::int::add 1000000000000000000000 99999999999999999
1000099999999999999999
(mpa-v0.11) 53 % mpa::int::mul 1001 9009
9018009
(mpa-v0.11) 54 % mpa::int::mul 10010001 9009009
90180189099009
(mpa-v0.11) 55 % mpa::float::pi 20
# Pi constant with 20 decimals, the result is cached in a namespace variable
3.14159265358979323846
(mpa-v0.11) 56 % time {mpa::float::pi 20};# result is cached in memory
363 microseconds per iteration
(mpa-v0.11) 57 % time {mpa::float::pi 21};# result is now recomputed
90643 microseconds per iteration
(mpa-v0.11) 58 % time {puts [mpa::float::pi 21]};# result is cached
3.141592653589793238462
4962 microseconds per iteration
(mpa-v0.11) 59 % mpa::float::add 1.0 2.0
3.0~2 # the precision with 1.0 ans 2.0 is assumed to be 0.1
# and the precision of the sum is the sum of the precisions
(mpa-v0.11) 60 % mpa::float::add 1.0000 2.0000
3.0000~2
(mpa-v0.11) 62 % mpa::float::format [mpa::float::mul 1.0000000 2.0000000];
# the precision of the product is approximatly A*Pb+B*Pa = 3e-7
2.000000 # now the number is formatted to be put on screen
(mpa-v0.11) 63 % mpa::float::mul 1.0000000 2.0000000
2.0000000~4 # precision is computed to be always the smallest ,
# even if such computations are complex to handle and loss of CPUSarnold This package is especially good when you want it to represent arbitrary floating-point numbers. See also : bignum in pure tcl.