This is documentation for Mathematica 3, which was
based on an earlier version of the Wolfram Language.
 Apply Apply[ f , expr ] or f @@ expr replaces the head of expr by f. Apply[ f , expr , levelspec ] replaces heads in parts of expr specified by levelspec. Examples: Apply[f, a, b, c ]; Apply[Plus, g[a, b]]. Level specifications are described in Section A.3.6. The default value for levelspec in Apply is {0}. Examples: Apply[f, a,b , c,d ]. Apply[f, a,b , c,d , 1 ]. Apply[f, a , -2]. See the Mathematica book: Section 1.8.11, Section 2.2.3. See also: Map, Scan, Level, Operate, MapThread. Further Examples This substitutes New for Old at the head of the expression using the shorthand notation for Apply. (Neither New nor Old has a built-in meaning in Mathematica.) In[1]:= Out[1]= The head of a product is Times; the head of a list is List. (You can see heads explicitly using FullForm[].) In[2]:= Out[2]= This changes a line into a polygon. In[3]:= Out[3]= This constructs a list of circles from a list of pairs of centers and radii. In[4]:= Out[4]=