2.3.12 Verbatim Patterns

Verbatim patterns.

Here the x_ in the rule matches any expression.

In[1]:= {f[2], f[a], f[x_], f[y_]} /. f[x_] -> x^2

Out[1]=

The Verbatim tells Mathematica that only the exact expression x_ should be matched.

In[2]:= {f[2], f[a], f[x_], f[y_]} /. f[Verbatim[x_]] -> x^2

Out[2]=