scheme - SICP - Which functions converge to fixed points? -
in chapter 1 on fixed points, book says can find fixed points of functions using
f(x) = f(f(x)) = f(f(f(x))) ....
what functions?
it doesn't work y = 2y when rewrite y = y/2 works
does y need smaller everytime? or there general attributes function has have find fixed points method?
what conditions should satisfy work?
according banach fixed-point theorem, such point exists iff mapping (function) contraction. means that, example, y=2x
doesn't have fixed point , y = 0,999... * x
has. in general, if f
maps [a,b]
[a,b]
, |f(x) - f(y)|
should equal c * |x - y|
0 <= c < 1
(for x, y
[a, b]).
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