We need to distinguish between two broad species of functions, as follows:
- Scalar functions: They apply to individual values and compute an individual result. Functions such as abs(), pow(), and the entire math module are examples of scalar functions.
- Collection functions: They work with iterable collections.
We can further subdivide the collection functions into three subspecies:
- Reduction: This uses a function to fold values in the collection together, resulting in a single final value. For example, if we fold (+) operations into a sequence of integers, this will compute the sum. This can be also be called an aggregate function, as it produces a single aggregate value for an input collection.
- Mapping: This applies a scalar function to each individual item of a collection; the result is a collection of the same size.
- Filter: This...
