Distance between Element and Subset of Real Numbers/Examples/Example 3

Example of Distance between Element and Subset of Real Numbers
Let $S \subseteq \R$ be the subset of the set of real numbers $\R$ defined as:
 * $S := \closedint 1 2$

Then:
 * $\map d {3, S} = 1$

where $d$ denotes the distance function.