The code below does not work. Can anyone tell me why? Thanks!
For[t = -1, t <= 1, t = t + 0.01,
For[z = -1, z <= 1, z = z + 0.01, If[t*z == 0, Print[t, ", ", z]]]]
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1 Answer
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It's the result of error accumulation of float number:
Nest[# + 0.01 &, -1, 100]
% == 0
(* 7.5287*10^-16 *)
(* False *)
There're many ways to fix this, for example, using arbitrary-precision number. In your case a Precision of 1. is enough:
0.01`1 // Precision
Nest[# + 0.01`1 &, -1, 100]
% == 0
(* 1. *)
(* 0.*10^-1 *)
(* True *)
Or simply use exact number:
Nest[# + 1/100 &, -1, 100]
% == 0
(* 0 *)
(* True *)
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$\begingroup$ What if I have a function gives numerical values, for example, if I have something like f(0.01,0.02)=0.2312, and I want to check if f(a,b)==0, how should I do this? $\endgroup$– lolJul 4, 2016 at 18:19
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$\begingroup$ @lol This depends on the structure of the function $\endgroup$– xzczdJul 5, 2016 at 2:25