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Recursive implementation of map filter reduce in Python
- 高洛峰Original
- 2016-10-18 14:32:571333browse
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,seq,x: [x] if seq==[] else [x] +scanl(f, seq[1:], f(x,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,y: ''.join( ['(',x,'+',y,')'] ), map(str,range(1,5)), '0') #Out: #['1', '2', '3', '5', '8'] #[0, 2, 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)']
Recursive implementation of map filter reduce in Python, note: be careful of memory overflow
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