Functions that create values are easier to combine in new ways than functions that directly perform side effects.

You should imagine variables as tentacles, rather than boxes. They do not contain values; they grasp them – two variables can refer to the same value.

How difficult it is to find a good name for a function is a good indication of how clear a concept it is that.

The best way to learn the value of good interface design is to use lots of interfaces – some good, some bad. Experience will teach you what works and what doesn’t. Never assume that a painful interface is “just the way it is.” Fix it, or wrap it in.

Below the surface of the machine, the program moves. Without effort, it expands and contracts. In great harmony, electrons scatter and regroup. The forms on the monitor are but ripples on the water. The essence stays invisibly below. – Master Yuan-Ma, The Book of Programming.

Learning is hard work, but everything you learn is yours and will make subsequent learning easier.

You’re building your own maze, in a way, and you might just get lost in it.

In the happy land of elegant code and pretty rainbows, there lives a spoil-sport monster called inefficiency.

Higher-order functions allow us to abstract over actions, not just values.

Programming, it turns out, is hard. The fundamental rules are typically simple and clear. But programs built on top of these rules tend to become complex enough to introduce their own rules and complexity. You’re building your own maze, in a way, and you might just get lost in it.