List of Figures

Chapter 1. Introducing functional programming

Figure 1.1. Modifying data in place can give concurrent threads an incorrect view of the data

Figure 1.2. The functional approach: creating a new, modified version of the original structure

Figure 1.3. A mathematical function is a mapping between the elements of two sets.

Figure 1.4. Where takes a predicate function as input.

Figure 1.5. A HOF that iteratively applies the function given as an argument

Figure 1.6. A HOF that conditionally applies the function given as an argument

Figure 1.7. A HOF that produces a function that’s given as input to another HOF

Figure 1.8. A HOF that wraps a given function between setup and teardown logic

Figure 1.9. HOFs call back into the calling function.

Chapter 2. Why function purity matters

Figure 2.1. A program where I/O can easily be isolated

Figure 2.2. Business scenario: validating a transfer request

Figure 2.3. Testing a pure function is easy.

Figure 2.4. An impure function from the perspective of testability

Chapter 3. Designing function signatures and types

Figure 3.1. An honest function does exactly what the signature says.

Figure 3.2. A dishonest function can have an outcome that isn’t accounted for in the signature.

Figure 3.3. An object or tuple as a Cartesian product

Figure 3.4. Option<T> is the union of the set Some(T) with the singleton set None.

Figure 3.5. Parsing a string as an int is a partial function

Figure 3.6. Converting from int to Age can also be modeled with Option.