principle of least surprise

[Kostis Sagonas]

 > > Nor do I really see the point of two collections of
 > > nearly-identical type test primitives (is_X/1 vs X/1).
 >
 > the question is better stated as why adding is_X/1 when there already 
 > exists X/1?

One of the reasons is the following:

Eshell V5.5  (abort with ^G)
1> float(3.1).
3.10000
2> is_float(3.1).
true


Kostis