Line 2,375: |
Line 2,375: |
| The connection in question is a boolean function on the variables <math>x, y\!</math> that returns a value of <math>\underline{1}</math> just when just one of the pair <math>x, y\!</math> is not equal to <math>\underline{1},</math> or what amounts to the same thing, just when just one of the pair <math>x, y\!</math> is equal to <math>\underline{1}.</math> There is clearly an isomorphism between this connection, viewed as an operation on the boolean domain <math>\underline\mathbb{B} = \{ \underline{0}, \underline{1} \},</math> and the dyadic operation on binary values <math>x, y \in \mathbb{B} = \operatorname{GF}(2)</math> that is otherwise known as <math>x + y\!.</math> | | The connection in question is a boolean function on the variables <math>x, y\!</math> that returns a value of <math>\underline{1}</math> just when just one of the pair <math>x, y\!</math> is not equal to <math>\underline{1},</math> or what amounts to the same thing, just when just one of the pair <math>x, y\!</math> is equal to <math>\underline{1}.</math> There is clearly an isomorphism between this connection, viewed as an operation on the boolean domain <math>\underline\mathbb{B} = \{ \underline{0}, \underline{1} \},</math> and the dyadic operation on binary values <math>x, y \in \mathbb{B} = \operatorname{GF}(2)</math> that is otherwise known as <math>x + y\!.</math> |
| | | |
− | The same connection <math>F : \underline\mathbb{B}^2 \to \underline\mathbb{B}</math> can also be read as a proposition about things in the universe <math>X = \underline\mathbb{B}^2.</math> If <math>s\!</math> is a sentence that denotes the proposition <math>F,\!</math> then the corresponding assertion says exactly what one states in uttering the sentence <math>^{\backprime\backprime} ~x~ \operatorname{is~not~equal~to} ~y~ ^{\prime\prime}.</math> In such a case, one has <math>\downharpoonleft s \downharpoonright ~=~ F,</math> and all of the following expressions are ordinarily taken as equivalent descriptions of the same set: | + | The same connection <math>F : \underline\mathbb{B}^2 \to \underline\mathbb{B}</math> can also be read as a proposition about things in the universe <math>X = \underline\mathbb{B}^2.</math> If <math>s\!</math> is a sentence that denotes the proposition <math>F,\!</math> then the corresponding assertion says exactly what one states in uttering the sentence <math>^{\backprime\backprime} \, x ~\operatorname{is~not~equal~to}~ y \, ^{\prime\prime}.</math> In such a case, one has <math>\downharpoonleft s \downharpoonright \, = F,</math> and all of the following expressions are ordinarily taken as equivalent descriptions of the same set: |
| + | |
| + | {| align="center" cellpadding="8" width="90%" |
| + | | |
| + | <math>\begin{array}{lll} |
| + | [| \downharpoonright s \downharpoonleft |] |
| + | & = & [| F |] |
| + | \\ |
| + | \\ |
| + | & = & F^{-1} (\underline{1}) |
| + | \\ |
| + | \\ |
| + | & = & \{~ (x, y) \in \underline\mathbb{B}^2 ~:~ s ~\} |
| + | \\ |
| + | \\ |
| + | & = & \{~ (x, y) \in \underline\mathbb{B}^2 ~:~ F(x, y) = \underline{1} ~\} |
| + | \\ |
| + | \\ |
| + | & = & \{~ (x, y) \in \underline\mathbb{B}^2 ~:~ F(x, y) ~\} |
| + | \\ |
| + | \\ |
| + | & = & \{~ (x, y) \in \underline\mathbb{B}^2 ~:~ \underline{(}~x~,~y~\underline{)} = \underline{1} ~\} |
| + | \\ |
| + | \\ |
| + | & = & \{~ (x, y) \in \underline\mathbb{B}^2 ~:~ \underline{(}~x~,~y~\underline{)} ~\} |
| + | \\ |
| + | \\ |
| + | & = & \{~ (x, y) \in \underline\mathbb{B}^2 ~:~ x ~\operatorname{exclusive~or}~ y ~\} |
| + | \\ |
| + | \\ |
| + | & = & \{~ (x, y) \in \underline\mathbb{B}^2 ~:~ \operatorname{just~one~true~of}~ x, y ~\} |
| + | \\ |
| + | \\ |
| + | & = & \{~ (x, y) \in \underline\mathbb{B}^2 ~:~ x ~\operatorname{not~equal~to}~ y ~\} |
| + | \\ |
| + | \\ |
| + | & = & \{~ (x, y) \in \underline\mathbb{B}^2 ~:~ x \nLeftrightarrow y ~\} |
| + | \\ |
| + | \\ |
| + | & = & \{~ (x, y) \in \underline\mathbb{B}^2 ~:~ x \neq y ~\} |
| + | \\ |
| + | \\ |
| + | & = & \{~ (x, y) \in \underline\mathbb{B}^2 ~:~ x + y ~\}. |
| + | \end{array}</math> |
| + | |} |
| | | |
| <pre> | | <pre> |
− | [| -[S]- |] = [| F |]
| |
− |
| |
− | = F^(-1)(%1%)
| |
− |
| |
− | = {<x, y> in %B%^2 : S}
| |
− |
| |
− | = {<x, y> in %B%^2 : F(x, y) = %1%}
| |
− |
| |
− | = {<x, y> in %B%^2 : F(x, y)}
| |
− |
| |
− | = {<x, y> in %B%^2 : -(x, y)- = %1%}
| |
− |
| |
− | = {<x, y> in %B%^2 : -(x, y)- }
| |
− |
| |
− | = {<x, y> in %B%^2 : x exclusive-or y}
| |
− |
| |
− | = {<x, y> in %B%^2 : just one true of x, y}
| |
− |
| |
− | = {<x, y> in %B%^2 : x not equal to y}
| |
− |
| |
− | = {<x, y> in %B%^2 : x <=/=> y}
| |
− |
| |
− | = {<x, y> in %B%^2 : x =/= y}
| |
− |
| |
− | = {<x, y> in %B%^2 : x + y}.
| |
− |
| |
| Notice the slight distinction, that I continue to maintain at this point, | | Notice the slight distinction, that I continue to maintain at this point, |
| between the logical values {false, true} and the algebraic values {0, 1}. | | between the logical values {false, true} and the algebraic values {0, 1}. |