[sage-support] maa-sage wiki page?

[David Joyner]

Hi:
Does anyone know what happened to http://wiki.sagemath.org/maa-sage ?
It was non-empty at some point (I announced it on sage-edu and
have a link posted to my USNA webpage. Google even has
a cache snapshot saying it was edited in November.)
Now it does not exist.
- David Joyner

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[sage-support] A Mac OS X Sage Launcher

[ahauskne...@umassd.edu]

Hi all,

It is easy to create an AppleScript applet that will launch sage
provided it is saved in the Applications folder. Here is the
text of the script:

 tell application "Terminal"
do script "/Applications/sage/sage"
end tell

The script can be saved as a double-clickable application with
its own icon.

Let me know if you would like a copy of the version I created with its
own "sage" icon (based on the sage logo).

Adam

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[sage-support] Arbitrary precision in cython

[Paul Zimmermann]

   Hi,

Jason Grout wrote:

> sage: pari(RealField(500)(10)).eint1().python()
> 4.15696892968532427740285981027818038434629008241953313262759569712786222819608803586147163177527802101305497591041862309918139192016097135380721447598904e-6
> sage: RealField(500)(10).eint()
> 2492.22897624187775913844014399852484898964710143094234538818526713774122742888744417794599665663156560488342454657568480015672868779475213684965774390
> sage:
> sage: pari(RealField(500)(-10)).eint1().python()
> -2492.22897624187775913844014399852484898964710143094234538818526713774122742888744417794599665663156560488342454657568480015672868779475213684965774390402
> sage: RealField(500)(-10).eint()
> NaN

the RealField() results correspond to the definition of eint in mpfr:

 -- Function: int mpfr_eint (mpfr_t Y, mpfr_t X, mp_rnd_t RND)
 Set Y to the exponential integral of X, rounded in the direction
 RND.  For positive X, the exponential integral is the sum of
 Euler's constant, of the logarithm of X, and of the sum for k from
 1 to infinity of X to the power k, divided by k and factorial(k).
 For negative X, the returned value is NaN.

and Carl Witty wrote:

> Actually, Sage doesn't print the entire value for floating-point
> numbers by default; it leaves a few digits off the end, so the
> potential binary->decimal conversion error above is a lot more than
> 1/2 ulp.  To get the entire within-1/2-ulp decimal value, you can use:
>
> sage: RealField(150)(10).eint().str(truncate=False)
> '2492.2289762418777591384401439985248489896471010'

thank you Carl for pointing out that. This means that the total error is
less that 1/2 ulp on the binary value, plus 1/2 ulp on the decimal conversion
(with truncate=False), or plus 0.5005 ulp on the default printing if 3 digits
are left off (assuming rounding to nearest).

Paul Zimmermann

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