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Consider the following two cases. |
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Case 1: All stages terminate. In this case, let f = j p(0). Clearly, the range of f contains indexes only for f. Hence, . However, M on f makes infinitely many mind changes; hence, . |
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Case 2: Some stage s starts but fails to terminate. In this case let fl = j p(2s+1) and f2 = j p(2s+2). Clearly, both fl and f2 are in and, for infinitely many x, . However, M(f1) = M(f2) = M( j p(0)[xs]). Thus M fails to Ex*-identify at least one of f1 and f2. |
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From the above cases it follows that . |
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6.11 Corollary . |
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§6.1.3 Behaviorally Correct Function Identification with Anomalies |
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The previous two subsections investigated two ways of liberalizing the Ex criterion of successful learning. These two means are combined in the following definition. |
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6.12 Definition (Case and Smith [35]) Let . |
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(a) M Bca-identifies f (written: ) just in case for all but finitely many n, j M(f[n]) = a f. |
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(b) . |
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Thus, a scientist Bca-identifies function f just in case, being fed the graph of f, she produces an infinite sequence of hypotheses, p0, p1, p2, . . . such that for all but finitely many n, pn is an index for an a-variant of f. It is easy to see that . The next proposition shows that these containments are strict. |
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6.13 Proposition (Case and Smith [35]) |
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(a) For each , ![0133-011.gif](0133-011.GIF) |
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(b) ![0133-012.gif](0133-012.GIF) |
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