`ALIAS` uses a special mechanism to convert an expression into an
equivalent C++ sentence that can be interval evaluated. This
conversion is based on the conversion of the expression into
a string in which all mathematical functions are substituted
by their interval equivalent. This causes a problem if rational
numbers are present in the expression as rational such as
1/6 will lead to 0 in C++. This procedure returns a string that
describes the interval equivalent of the expression in which
rational such as 1/6 as 1./6. and constant such as Pi have been
converted into their C++ equivalent.
For example

Convert_Frac_Cons(1/6*Sin(v_IS(1))+Pi+2/3*Cos(v_IS(2))); 1./6.Sin(v_IS(1))+BiasPi+2./3.*Cos(v_IS(2))

Jean-Pierre Merlet 2012-12-20