Algorithm Groups

The STL divides the algorithm library into four groups:

• Nonmodifying sequence operations

• Mutating sequence operations

• Sorting and related operations

• Generalized numeric operations

The first three groups are described in the algorithm (formerly algo.h) header file, and the fourth group, being specifically oriented toward numeric data, gets its own header file, called numeric. (Formerly, they, too, were in algo.h.)

Nonmodifying sequence operations operate on each element in a range. These operations leave a container unchanged. For example, find() and for_each() belong to this category.

Mutating sequence operations also operate on each element in a range. As the name suggests, however, they can mutate, or change, the contents of a container. The change could be in values or in the order in which the values are stored. The transform(), random_shuffle(), and copy() functions fall into this category.

Sorting and related operations include several sorting functions (including sort()) and a variety of other functions, including the set operations.

The numeric operations include functions to sum the contents of a range, calculate the inner product of two containers, calculate partial sums, and calculate adjacent differences. Typically, these are operations that are characteristic of arrays, so vector is the container most likely to be used with them.

Appendix G provides a complete summary of these functions.