Uses for MapAll ( //@ )

Question

The function MapAll was seen as important enough to warrant the short form //@, yet I rarely use it, especially compared to others like /@

Answer 1

I would use it as a lazy way to apply algebraic expressions on objects algebraic functions do not work with:

In[13]:= ser = 1/(1 + x)^a + O[x]^4

Out[13]= SeriesData[x, 0, {
 1, -a, Rational[1, 2] (a + a^2), 
  Rational[1, 6] ((-2) a - 3 a^2 - a^3)}, 0, 4, 1]

In[14]:= Factor[ser]

Out[14]= SeriesData[x, 0, {
 1, -a, Rational[1, 2] (a + a^2), 
  Rational[1, 6] ((-2) a - 3 a^2 - a^3)}, 0, 4, 1]

In[15]:= MapAll[Factor, ser]

Out[15]= SeriesData[x, 0, {
 1, -a, Rational[1, 2] a (1 + a), 
  Rational[-1, 6] a (1 + a) (2 + a)}, 0, 4, 1]