The Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.


Math Forum » Discussions » Inactive » comp.soft-sys.math.mathematica

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: Truth in inequalities
Replies: 4   Last Post: Jun 16, 2001 3:02 AM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Jack Goldberg

Posts: 53
Registered: 12/7/04
Truth in inequalities
Posted: Jun 14, 2001 2:50 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Hi group,

Can someone explain the logic of the following:

x < Infinity returns x < Infinity
while
x - Infinity < 0 returns True

I should mention that I am aware of the fact that x - Infinity simplifies
automatically to -Infinity which is then compared to 0 and found wanting.
The issue I'm raising is why should a CAS that has x-Infinity < 0 return
True not also return True for the x < Infinity? One awkwardness of
having this difference of behavior can be seen in the example,

MyFunction[x_,y_]/;(x<y) := blah

and

MyFunction[x_,y_]/;(x-y<0) := blah

do not do the same thing when, say, y=Infinity.

Just curious :-)

Jack







Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.