[Maxima-discuss] Need for apply_nouns

[Stern, M. (NIH/NIA/I. [E] <st...@ma...>]

Macsyma has a function apply_nouns which maxima lacks.  Syntax is appy_nouns(expr) or optionally appy_nouns(expr, nouns).  According to the Macsyma manual this has the same effect as ev(expr,'nouns) but is faster and uses less memory.  In fact, I find that they are NOT equivalent.

F(x):=x^2
apply_nouns(factor('f(x)-1),'f) gives x^2-1

whereas

ev(factor('f(x)-1),'f) gives (x+1)*(x-1)

In other words, ev is not a normal function, it is sneaky and looks inside expressions to evaluate from the inside out.  This means ev(expr,'nouns) is NOT a replacement for apply_nouns in old Macsyma code.  We need a real version.