logscale base bug

[Allin C. <cot...@wf...>]

The help for logscale doesn't state that the base must be 
integral, but at present user input is truncated to an integer
and you can have this kinda funny dialog with gnuplot:

gnuplot> set logscale y 1.5
                           ^
         log base must be >= 1.1; logscale unchanged

This happens because on line 2054 of set.c we have

newbase = abs(real_expression());

If the intent is to support non-integral bases (e.g. natural 
logs), this should be

newbase = fabs(real_expression());

since abs() returns an int.

Note: the "abs()" formulation is new as of revision 1.241 of 
set.c (Jan 2007); before that newbase was set as

newbase = magnitude(const_express(&a));

which preserved the non-integral part.

-- 
Allin Cottrell
Department of Economics
Wake Forest University, NC