Go Idioms

Make the zero value useful by initializing internal state lazily on first use rather than requiring explicit construction. In the gmp package, the Int struct uses an init boolean flag to track if the underlying C mpz_t has been initialized, and the doinit method calls C.mpz_init only if the flag is false.

type Int struct {
	i    C.mpz_t
	init bool
}

func (z *Int) doinit() {
	if z.init {
		return
	}
	z.init = true
	C.mpz_init(&z.i[0])
}

This ensures that var x Int creates a valid zero value (representing 0) without crashing, bridging the gap between Go's zero-value convention and C libraries that require explicit initialization.

Go Idioms: Make the Zero Value Useful ensures that a variable created with default values works immediately without needing a special setup function. It is like a light bulb that turns on automatically the first time you try to use it, rather than requiring you to flip a switch before plugging it in. You use this when wrapping external libraries that don't support default initialization.