Re: [Haskell-cafe] custom SQL-to-Haskell type conversion in HDBC

On Friday, August 19, 2011, Brandon Allbery wrote:

On Fri, Aug 19, 2011 at 11:45, Erik Hesselink wrote:

...

Note that PostgreSQL also doesn't work with decimals as precision:

postgres=# select 1::decimal(4,2) * 1::decimal(4,2); ?column? ---------- 1.0000 (1 row)

That should be 1.00 instead if you want the precision correctly

represented.

Er? Last I checked, that was exactly how precision worked over multiplication; otherwise you are incorrectly discarding precision present in the original values. Unless you're assuming the OP actually wants an incorrect flat precision model....

This is the way I was taught to do it in physics. See also http://en.m.wikipedia.org/wiki/Significance_arithmetic Erik

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