safeDivide: Some simple arithmetic and logic functions for use in GP expressions
Description
safeDivide a division operator that returns 0 if the divisor is 0.
safeLn a natural logarithm operator that return 0 if its argument is less
then 0.
ln is the natural logarithm.
positive returns true if its argument is greater then 0.
ifPositive returns its second argument if its first argument is positive,
otherwise its third argument.
ifThenElse returns its second argument if its first argument is TRUE,
otherwise its third argument.
Usage
safeDivide(a, b)
safeSqroot(a)
safeLn(a)
ln(a)
positive(x)
ifPositive(x, thenbranch, elsebranch)
ifThenElse(x, thenbranch, elsebranch)
Arguments
thenbranch
The element to return when x is TRUE.
elsebranch
The element to return when x is FALSE.