define a Program Variable. In contrast to set(),
def() remembers the definition (ie, the mathematical formula) of
numerical Program Variables. This is especially useful for complex math
expressions used in non-linear least squares fits.
Input Program Variables
The keyword is taken as the name of the variable to
be assigned, and the Value is taken as the mathematical expression to use
for the definition.
Output Program Variables
def() is the default command and so is optional. That
is, simply typing a = b is equivalent to def a = b.
Iff> def (b = a + 1, c = 100 * sqrt(b) )
Iff> def my.chik = my.chi * my.k^kweight
Note that both b and c will change if a changes, and
that my.chik will automatically update when kweight changes.