Skill 如何Flatten一个list

https://www.cnblogs.com/yeungchie/

• code

unless(fboundp('ycFlattenList)
	procedure(ycFlattenList(listin @optional keep(nil))
		prog((output havep)
			foreach(arg listin
				cond(
					(listp(arg)
						case(keep
							(nil
								output = append(output ycFlattenList(arg keep))
							)
							(t
								havep = nil
								foreach(x arg
									if(listp(x) havep = t)
								)
								if(havep
									output = append(output ycFlattenList(arg keep))
									output = append1(output arg)
								)
							)
						)
					)
					(t
						output = append1(output arg)
					)
				);cond
			);foreach
			return(output)
		);prog
	);ycFlattenList
)

• describe

1. 输入一个list，返回一个被Flatten的list。
2. 可以指定第二参数keep为t，用来保留最后一级list；keep默认为nil。（这是我在某个特殊场景下的需求）

• example

ycFlattenList('((1 2) 3 (4 (5 6))))
=>(1 2 3 4 5 6)
ycFlattenList('((1 2) 3 (4 (5 6))) t)
=>((1 2) 3 4 (5 6))