Many Happy Returns

A novice monk said to master Kaimu, “I have heard that it is preferable to have only one return statement in a function. Do you agree?”

Kaimu asked, “Where is your bowl?”

The monk apologized and left to fetch his bowl.

When the monk returned, he showed his bowl to the master and said, “I have heard that it is preferable to have only one return statement in a function. Do you agree?”

Kaimu asked, “Why is there no rice in your bowl?”

The monk apologized and left to fetch some rice.

When the monk returned, he showed his bowl full of steaming white rice to the master and said, “I have heard that it is preferable to have only one return statement in a function. Do you agree?”

Kaimu took the monk’s bowl and placed it on his desk.

“You speak of a most venerable design principle, known as Single-Entry Single-Exit,” said the master. He then told the monk of the glorious days of coding long past, when memory was low, hardware was slow, and resources had to be managed with care. “For C did you no favors,” said Kaimu, “and Assembly did half as many as that. So if your function borrowed a thing, then your function had to put it back. And how was this most easily done? By putting all the cleanup code in one place, at the function’s bottom... a tradition that continues to this day.”

Kaimu then spoke of the birth of objects, of destructors and finalizers. He spoke of garbage collection too; of reference counting and mark-and-sweep, and compilers that could tell when an object went out of scope. He spoke of buffers that grew as needed and vanished when not, of files that closed themselves, of connection pools and thread pools and try-with-resources, and of how wondrous and magical was the modern bestiary of languages, where monks could devote their energies to more interesting problems instead of fussing about with malloc and free and goto fail.

“Yes,” said the weary monk at last. “But do you agree with the design principle of Single-Entry Single-Exit, or do you not?”

Kaimu looked down and said, “Why is the rice in your bowl white, and not brown?”