Is n() the same as N() if not why not

asked 2012-01-17 18:29:55 +0100

russ_hensel
65 ●6 ●9 ●14

updated 2012-01-17 19:41:33 +0100

I am trying to use Sage as a simple numerical calculator but sometimes have to fight with more advanced features, things I think are number are not. I starting using n() to fix this up, but in some cases it did not work. Bug big N N() did. Is this the way it is supposed to be ( if so why ). Identical commands ( symbols..... ) except for capitilization seems like a bad idea. Here is the code:

# Is n() the same as N() if not why not


xll = 1. / ( pi * ( 2. ^ .5 )   ) 

xll = 22. * 2

print "xll is of type", type( xll )
print ""

print "Big N next" 
print N( ll )

print "" 
print "Little n next" 
print n( xll )

produced output:

xll is of type <type 'sage.rings.real_mpfr.RealNumber'>

Big N next 
0.0000120042175487614

Little N next 
Traceback (click to the left of this block for traceback) ...       
TypeError: 'sage.rings.real_mpfr.RealLiteral' object is not callable

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2 Answers

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answered 2012-01-17 18:50:24 +0100

DSM

5242 ●21 ●68 ●112

updated 2012-01-17 21:30:05 +0100

n() is N() -- they're different names for exactly the same function, so they'll give exactly the same answers.. at least if n and N are still what they started as.

Could you cut and paste the output that shows they're different? Usually when something like this happens, either (1) a function has been replaced, say because someone typed "n = something_or_other", or (2) there's a simple typo.

(BTW, your code confuses me a little-- you assign to xll twice but print N(ll), where ll is never defined.)

UPDATE: Thanks for posting the traceback. [Although it's not the output from the code you posted -- the capitalization in 'Little n next' is different between the two, so you must've changed something.]

The traceback makes it clear that my guess #1 was right: you've accidentally set n, little n, to a real number. Type "print n" to see what the number is. The error message is saying that a RealLiteral can't be called (which makes sense, it's not really a function.)

For example:

sage: n(pi)
3.14159265358979
sage: n = 3.45 
sage: n(pi)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/Applications/sage/local/lib/python2.6/site-packages/sage/all_cmdline.pyc in <module>()
[...]
TypeError: 'sage.rings.real_mpfr.RealLiteral' object is not callable