*To*: mathgroup@smc.vnet.net*Subject*: [mg12131] RE: [mg12048] Very odd behaviour in Mod/N*From*: R Finley <trfin@umsmed.edu>*Date*: Mon, 27 Apr 1998 01:46:15 -0400

Hi Your problem is evidently occurring when you exceed the numerical precision of the system you are working with (typically 16 digits)... ut try the following: pie ationalize[N[Pi,20],0] Q 0^18 t od[Q,2 pie] N[t] N[t,20] Regards, RF -----Original Message----- From: Adrian Cable [SMTP:megalith@jimc.demon.co.uk] To: mathgroup@smc.vnet.net Sent: Friday, April 24, 1998 12:52 AM To: mathgroup@smc.vnet.net Subject: [mg12048] Very odd behaviour in Mod/N Hi there, I've observed some very odd behaviour when using Mod and N. It seems that, when handling very large numbers, Mathematica (3.0.1, Win32) does not display machine-precision results correctly. Here's an example which behaves as it should: In[12]: 0^8 Out[12]00000000 In[13]: od[Q, 2 Pi] Out[13]00000000 - 31830988 Pi In[14]:[t] Out[14].9427 In[15]:[t, 20] Out[15].9426951345040144600 Now for a very similar example which obviously behaves wrongly: In[16]: 0^18 Out[16]000000000000000000 In[17]: od[Q, 2 Pi] Out[17]000000000000000000 - 318309886183790670 Pi In[18]:[t] Out[18]28. In[19]:[t, 20] Out[19].831039164951128133 What exactly is going on here? Thanks, cheers, Adrian Cable.