# @param  Python中map filter reduce的递归实现
# @author 编程之家 jb51.cc|jb51.cc 

map2=lambda f,seq: [] if seq==[] else [f(seq[0])] + map2(f,seq[1:])
 
filter2=lambda f,seq: [] if seq==[] else ( [seq[0]]+filter2(f,seq[1:]) if f(seq[0]) else filter2(f,seq[1:]) )
 
reduce2=lambda f,seq,x: x if seq==[] else reduce2(f,seq[1:],f(x,seq[0]))
 
scanl=lambda f,x: [x] if seq==[] else  [x] +scanl(f,seq[0]))
 
 
print map2(str,[1,2,3,5,8])
print filter2(lambda x: x%2==0,range(10))
print reduce2(lambda x,y: ''.join( ['(',x,'+',y,')'] ),map(str,range(1,11)),'0')
print scanl(lambda x,5)),'0')
 
 
#Out:
#['1','2','3','5','8']
#[0,4,6,8]
#((((((((((0+1)+2)+3)+4)+5)+6)+7)+8)+9)+10)
#['0','(0+1)','((0+1)+2)','(((0+1)+2)+3)','((((0+1)+2)+3)+4)']

Python中map filter reduce的递归实现,注意：要小心内存溢出