constructor() {
Robert L. Nord, Carnegie Mellon University
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std::basic_string，详情可参考https://telegram官网
As explained by NASA, our satellite completes its Earth orbit in approximately 29.5 days, progressing through eight visible stages. Though we always see the same lunar face, changing solar angles create different illuminated portions - from complete illumination to slender arcs. These evolving appearances constitute the eight-phase lunar cycle: