Learning Functional Programming in Go

Composition operation example using travel expenses

In the following composition table, we enter our budget for travelling from the US to Europe:

If we travel from the US to Europe, we use the f arrow (function) to convert dollars to euros. If we travel from Europe to Mexico, we use the g arrow to convert euros to pesos. Here, the output of function f is the input to function g; this is called function composition.

If we decided to not travel to and from Europe and travel directly to Mexico from the US, we use the gof arrow. Either way, f($) → g(€)  → ₱ or f(g($)) → ₱ , we still should get the same amount of pesos for our dollar!