func minmax()

in starlark/library.go [690:755]
63 lines of code
14 McCabe index (conditional complexity)

func minmax(thread *Thread, b *Builtin, args Tuple, kwargs []Tuple) (Value, error) {
	if len(args) == 0 {
		return nil, fmt.Errorf("%s requires at least one positional argument", b.Name())
	}
	var keyFunc Callable
	if err := UnpackArgs(b.Name(), nil, kwargs, "key?", &keyFunc); err != nil {
		return nil, err
	}
	var op syntax.Token
	if b.Name() == "max" {
		op = syntax.GT
	} else {
		op = syntax.LT
	}
	var iterable Value
	if len(args) == 1 {
		iterable = args[0]
	} else {
		iterable = args
	}
	iter := Iterate(iterable)
	if iter == nil {
		return nil, fmt.Errorf("%s: %s value is not iterable", b.Name(), iterable.Type())
	}
	defer iter.Done()
	var extremum Value
	if !iter.Next(&extremum) {
		return nil, nameErr(b, "argument is an empty sequence")
	}

	var extremeKey Value
	var keyargs Tuple
	if keyFunc == nil {
		extremeKey = extremum
	} else {
		keyargs = Tuple{extremum}
		res, err := Call(thread, keyFunc, keyargs, nil)
		if err != nil {
			return nil, err // to preserve backtrace, don't modify error
		}
		extremeKey = res
	}

	var x Value
	for iter.Next(&x) {
		var key Value
		if keyFunc == nil {
			key = x
		} else {
			keyargs[0] = x
			res, err := Call(thread, keyFunc, keyargs, nil)
			if err != nil {
				return nil, err // to preserve backtrace, don't modify error
			}
			key = res
		}

		if ok, err := Compare(op, key, extremeKey); err != nil {
			return nil, nameErr(b, err)
		} else if ok {
			extremum = x
			extremeKey = key
		}
	}
	return extremum, nil
}