In comp.lang.pascal.ansi-iso message <f7OdnZKR3sNIXPfaRVnyuQA@[EMAIL PROTECTED]
>,
Thu, 20 Dec 2007 19:29:28, Richard Heathfield <rjh@[EMAIL PROTECTED]
>
posted:
>john said:
>
>> Hi, regarding Turbo Pascal 7.x (or the standard), is there any power
>> function provided?
>>
>> Something like
>>
>> power(10,4) meaning 10 ^4, or something similar.
>
>
>Pascal offers EXP and LN. N^P = EXP(P * LN(N)).
>
>Thus, 10^4 = EXP(4 * LN(10)).
The original example was an integer example, and you have given a float
method. I'm almost sure that your code will almost always give a float
of exact integer value (if in the exact range 0..2^53 for Double and
more for Extended). That may not be good enough.
For integer powers, one can use a multiplying loop, though that would
get slow for 1.000001^1000000 (which gives about e); in which case one
can be cunning as in (written in Borland, but perhaps generic) -
function ExpNum(const A : Xtype ; const B : longint) : Xtype ;
begin if B=0 then ExpNum := 1.0 else
if Odd(B) then ExpNum := ExpNum(A, B-1) * A
else ExpNum := Sqr(ExpNum(A, B div 2)) ;
end {ExpNum} ;
which would for that do about log2(1000000) = 20 recursions. It could
be rewritten iterative.
My <URL:http://www.merlyn.demon.co.uk/pas-math.htm>
refers.
With an integer number to be raised to a power, a multiplying loop can
never take unreasonably long, unless the number is -1 0 +1 or runtime
checks are off.
But the actual answer to the OP is "NO" or "NOT IN TP".
--
(c) John Stockton, Surrey, UK. ?@[EMAIL PROTECTED]
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