vec->length = len; for (size_t ix = 0; ix < len; ix++) vec->array[ix] = 0.0; return vec; } C++语言标准尚未支持灵活数组类型。但Visual C++2015支持。 Lesser known C features
all lesser numbers ... insomuch that a compleat Peal of changes on one number seemeth to be formed by uniting of the compleat Peals on all lesser numbers