[Axiom-developer] [#23 using exp as a symbol in ** ] (new)

[anonymous]

trigcat.spad

WS> ElementaryFunctionCategory(): Category == with
WS>     log : $ -> $       ++ log(x) returns the natural logarithm of x.
WS>     exp : $ -> $       ++ exp(x) returns %e to the power x.
WS>     "**": ($, $) -> $  ++ x**y returns x to the power y.
WS>  add
WS>    if $ has Monoid then
WS>      x ** y == exp(y * log x)

etc

The more such stuff I see, the better is my live experience,
the more efficient is bug identification progress.

Much thanks!

Vladimir


Sunday, January 16, 2005, 7:08:49 PM, you write:

WS> The error apparently comes from EXPR where the implementation is
WS>   x**y == exp(y * log(x))

WS> so exp^log(x) is computed as
 
WS>   exp(log(x) * log(exp))

WS> which should be ok, but then the system handles log exp and tries to 
simplify it
WS> to the identity map, and not finding the argument.

WS> William
WS> ---

>> 
>> Simpler:
>> 
>> (1) -> exp^3
>> 
>>            3
>>    (1)  exp
>>                                    Type: Polynomial Integer
>> (2) -> a^log(x)
>> 
>>          log(x)
>>    (2)  a
>>                                    Type: Expression Integer
>> (3) -> exp^log(x)
>> 
>>    >> System error:
>>    Cannot take first of an empty list
>> 
>> protected-symbol-warn called with (NIL)
>>





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