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===Commentary Note 11.9===
===Commentary Note 11.9===
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<pre>
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Among the vast variety of conceivable regularities affecting 2-adic relations, we pay special attention to the ''c''-regularity conditions where ''c'' is equal to 1.
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Among the vast variety of conceivable regularities affecting 2-adic relations,
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we pay special attention to the c-regularity conditions where c is equal to 1.
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<blockquote>
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<p>Let ''P'' ⊆ ''X'' × ''Y'' be an arbitrary 2-adic relation. The following properties of P can be defined:</p>
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| Let P c X x Y be an arbitrary 2-adic relation.
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{| cellpadding="4"
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| The following properties of P can be defined:
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| ''P'' is "total" at ''X''
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|
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| iff
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| P is "total" at X iff P is (>=1)-regular at X.
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| ''P'' is (≥1)-regular at ''X''.
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|
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|-
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| P is "total" at Y iff P is (>=1)-regular at Y.
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| ''P'' is "total" at ''Y''
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|
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| iff
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| P is "tubular" at X iff P is (=<1)-regular at X.
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| ''P'' is (≥1)-regular at ''Y''.
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|
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|-
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| P is "tubular" at Y iff P is (=<1)-regular at Y.
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| ''P'' is "tubular" at ''X''
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| iff
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| ''P'' is (≤1)-regular at ''X''.
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|-
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| ''P'' is "tubular" at ''Y''
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| iff
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| ''P'' is (≤1)-regular at ''Y''.
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|}
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</blockquote>
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We have already looked at 2-adic relations that
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We have already looked at 2-adic relations that separately exemplify each of these regularities.
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separately exemplify each of these regularities.
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Also, we introduced a few bits of additional terminology and
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Also, we introduced a few bits of additional terminology and special-purpose notations for working with tubular relations:
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special-purpose notations for working with tubular relations:
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| P is a "pre-function" P : X ~> Y iff P is tubular at X.
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:{| cellpadding="4"
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|
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| ''P'' is a "pre-function" ''P'' : ''X'' ~> ''Y''
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| P is a "pre-function" P : X <~ Y iff P is tubular at Y.
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| iff
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| ''P'' is tubular at ''X''.
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|-
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| ''P'' is a "pre-function" ''P'' : ''X'' <~ ''Y''
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| iff
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| ''P'' is tubular at ''Y''.
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|}
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Thus, we arrive by way of this winding stair at the very special stamps
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Thus, we arrive by way of this winding stair at the very special stamps of 2-adic relations ''P'' ⊆ ''X'' × ''Y'' that are "total prefunctions" at ''X'' (or ''Y''), "total and tubular" at ''X'' (or ''Y''), or "1-regular" at ''X'' (or ''Y''), more often celebrated as "functions" at ''X'' (or ''Y'').
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of 2-adic relations P c X x Y that are "total prefunctions" at X (or Y),
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"total and tubular" at X (or Y), or "1-regular" at X (or Y), more often
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celebrated as "functions" at X (or Y).
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<pre>
| If P is a pre-function P : X ~> Y that happens to be total at X, then P
| If P is a pre-function P : X ~> Y that happens to be total at X, then P
| is known as a "function" from X to Y, typically indicated as P : X -> Y.
| is known as a "function" from X to Y, typically indicated as P : X -> Y.