Poetry and functional languages
The word metaphor means, literally, to transfer.
A poem is a series of metaphors, of mappings, of transferrences, where the hovering finger points at the picture for bird, and then glides to the picture for love. It shows you how to transfer ideas, it gives you a route to take, it shows you how to see something new.
Just as a function is a pristine mapping between two languages, so too is the metaphor. And just as a chain of functions operates as a way of entering a room with a bird and leaving with love, so to does a series of metaphors.