A good example that many people are familiar with is parsing data. Compare these two approaches. You could write functions that manipulate the input and build up an output or you could create a structure that represents a grammar for the data you are parsing (perhaps by using a parser combinator library).
In the first approach, the only feasible way of reasoning about the program is operationally; when it gets to here, this function is called, causing ... . In the second approach, you can reason about the program by considering the grammar that you created. You don't need to know exactly how the parsing happens in order to understand a grammar. I argue that this is because the grammar has been given a meaning.
Parsing makes a good toy example, but this same technique of finding ways of giving meaning to components is applicable to software in the real world.
A good example that many people are familiar with is parsing data. Compare these two approaches. You could write functions that manipulate the input and build up an output or you could create a structure that represents a grammar for the data you are parsing (perhaps by using a parser combinator library).
In the first approach, the only feasible way of reasoning about the program is operationally; when it gets to here, this function is called, causing ... . In the second approach, you can reason about the program by considering the grammar that you created. You don't need to know exactly how the parsing happens in order to understand a grammar. I argue that this is because the grammar has been given a meaning.
Parsing makes a good toy example, but this same technique of finding ways of giving meaning to components is applicable to software in the real world.