Hi Community,
I seem to experience some problems when I try to use @@ to TraditionalForm input. I was expecting that Times@@a+b+c would return abc. As you can see from my notebook below, it doesn’t. Times@@Plus[a,b,c] yields the expected result. Anyone who can shine some light on this?
Many thanks in advance!
Try:
Times @@ (a + b + c)
Thank you Hans,
That worked. But why? What magic is hidden in the addition of the brackets?
Head[(a+b+c)] yields Plus. Exactly like Head[a+b+c].
Times @@ a + b + c
is the same as
(Times @@ a) + b + c
and
Times @@ a
is just a.
Side note, you’re not actually using TraditionalForm anywhere, and it’s not relevant to the issue. The issue is purely one of precedence.
Apply and Plus have different precedences:
In[1]:= Precedence[Apply]
Out[1]= 620.
In[2]:= Precedence[Plus]
Out[2]= 310.
The higher the precedence, the tighter it will bind a function/argument pair. This matters only when using infix notation. Bracketing overrides the precedence pairings.
Prefix notation is not affected by precedences, since the syntax itself decides order of evaluation:
Apply[Times, Plus[a, b, c]]
Postfix notation also generally works Ok:
a + b + c // Times @@ # &
Gentlemen,
Thank you for your excelent bits of wisdom that you so generously have shared with me. I know feel that my existence on this planet has reached a higher dimension. Made my day!