Re: [HACKERS] bug in numeric_power() function
I also have a question here: isn't dpow enough for calculation? Why added numeric_power? Tom Lane [EMAIL PROTECTED] дÈëÏûÏ¢ÐÂÎÅ:[EMAIL PROTECTED] Richard Wang [EMAIL PROTECTED] writes: I expected 0 ^ 123.3 to be 0, but it reported error as follows postgres=# select 0 ^ 123.3; ERROR: cannot take logarithm of zero Hmm, seems like the numeric and float8 power operators don't agree about 0^0 either... regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
[HACKERS] bug in numeric_power() function
I expected 0 ^ 123.3 to be 0, but it reported error as follows postgres=# select 0 ^ 123.3; ERROR: cannot take logarithm of zero I find that there is a bug in numeric_power() function the function caculates a ^ b based on the algorithm e ^ (lna * b) as you see, ln0 is not valid -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] bug in numeric_power() function
-Original Message- From: [EMAIL PROTECTED] [mailto:pgsql-hackers- [EMAIL PROTECTED] On Behalf Of Richard Wang Sent: Tuesday, March 11, 2008 7:38 PM To: pgsql-hackers@postgresql.org Subject: [HACKERS] bug in numeric_power() function I expected 0 ^ 123.3 to be 0, but it reported error as follows postgres=# select 0 ^ 123.3; ERROR: cannot take logarithm of zero I find that there is a bug in numeric_power() function the function caculates a ^ b based on the algorithm e ^ (lna * b) as you see, ln0 is not valid It seems an obvious work-around that: if (b == 0) return 1; if (a == 0) return 0; could be inserted at the top. Aside: Having the ^ operator overloaded for exponentiation surprises me. Does it really have the right precedence for performing exponentiation? (E.g. you cannot do this in C++ because ^ will have the precedence of xor, which is wrong). -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] bug in numeric_power() function
Richard Wang [EMAIL PROTECTED] writes: I expected 0 ^ 123.3 to be 0, but it reported error as follows postgres=# select 0 ^ 123.3; ERROR: cannot take logarithm of zero Hmm, seems like the numeric and float8 power operators don't agree about 0^0 either... regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
