This is documentation for Mathematica 5, which was
based on an earlier version of the Wolfram Language.

 1.8.6 Adding, Removing and Modifying List Elements Functions for manipulating elements in explicit lists. This gives a list with x prepended. In[1]:= Prepend[{a, b, c}, x] Out[1]= This inserts x so that it becomes element number 2. In[2]:= Insert[{a, b, c}, x, 2] Out[2]= This replaces the third element in the list with x. In[3]:= ReplacePart[{a, b, c, d}, x, 3] Out[3]= This replaces the element in a matrix. In[4]:= ReplacePart[{{a, b}, {c, d}}, x, {1, 2}] Out[4]= Functions like ReplacePart take explicit lists and give you new lists. Sometimes, however, you may want to modify a list "in place", without explicitly generating a new list. Resetting list elements. This defines v to be a list. In[5]:= v = {a, b, c, d} Out[5]= This sets the third element to be x. In[6]:= v[[3]] = x Out[6]= Now v has been changed. In[7]:= v Out[7]= Resetting pieces of matrices. This defines m to be a matrix. In[8]:= m = {{a, b}, {c, d}} Out[8]= This sets the first column of the matrix. In[9]:= m[[All, 1]] = {x, y}; m Out[9]= This sets every element in the first column to be 0. In[10]:= m[[All, 1]] = 0; m Out[10]=