Changes

update
Line 247: Line 247:  
|+ style="height:30px" | <math>\text{Table 1.} ~~ \text{Syntax and Semantics of a Calculus for Propositional Logic}\!</math>
 
|+ style="height:30px" | <math>\text{Table 1.} ~~ \text{Syntax and Semantics of a Calculus for Propositional Logic}\!</math>
 
|- style="height:40px; background:ghostwhite"
 
|- style="height:40px; background:ghostwhite"
 +
| <math>\text{Graph}\!</math>
 
| <math>\text{Expression}~\!</math>
 
| <math>\text{Expression}~\!</math>
 
| <math>\text{Interpretation}\!</math>
 
| <math>\text{Interpretation}\!</math>
 
| <math>\text{Other Notations}\!</math>
 
| <math>\text{Other Notations}\!</math>
 
|-
 
|-
| &nbsp;
+
| height="100px" | [[Image:Cactus Node Big Fat.jpg|20px]]
| <math>\text{True}\!</math>
+
| <math>~</math>
 +
| <math>\operatorname{true}</math>
 
| <math>1\!</math>
 
| <math>1\!</math>
 
|-
 
|-
| <math>\texttt{(~)}\!</math>
+
| height="100px" | [[Image:Cactus Spike Big Fat.jpg|20px]]
| <math>\text{False}\!</math>
+
| <math>\texttt{(~)}</math>
 +
| <math>\operatorname{false}</math>
 
| <math>0\!</math>
 
| <math>0\!</math>
 
|-
 
|-
| <math>x\!</math>
+
| height="100px" | [[Image:Cactus A Big.jpg|20px]]
| <math>x\!</math>
+
| <math>a\!</math>
| <math>x\!</math>
+
| <math>a\!</math>
 +
| <math>a\!</math>
 
|-
 
|-
| <math>\texttt{(} x \texttt{)}\!</math>
+
| height="120px" | [[Image:Cactus (A) Big.jpg|20px]]
| <math>\text{Not}~ x\!</math>
+
| <math>\texttt{(} a \texttt{)}~</math>
|
+
| <math>\operatorname{not}~ a</math>
<math>\begin{matrix}
+
| <math>\lnot a \quad \bar{a} \quad \tilde{a} \quad a^\prime</math>
x'
  −
\\
  −
\tilde{x}
  −
\\
  −
\lnot x
  −
\end{matrix}\!</math>
   
|-
 
|-
| <math>x~y~z\!</math>
+
| height="100px" | [[Image:Cactus ABC Big.jpg|50px]]
| <math>x ~\text{and}~ y ~\text{and}~ z\!</math>
+
| <math>a ~ b ~ c</math>
| <math>x \land y \land z\!</math>
+
| <math>a ~\operatorname{and}~ b ~\operatorname{and}~ c</math>
 +
| <math>a \land b \land c</math>
 
|-
 
|-
| <math>\texttt{((} x \texttt{)(} y \texttt{)(} z \texttt{))}\!</math>
+
| height="160px" | [[Image:Cactus ((A)(B)(C)) Big.jpg|65px]]
| <math>x ~\text{or}~ y ~\text{or}~ z\!</math>
+
| <math>\texttt{((} a \texttt{)(} b \texttt{)(} c \texttt{))}</math>
| <math>x \lor y \lor z\!</math>
+
| <math>a ~\operatorname{or}~ b ~\operatorname{or}~ c</math>
 +
| <math>a \lor b \lor c</math>
 
|-
 
|-
| <math>\texttt{(} x ~ \texttt{(} y \texttt{))}\!</math>
+
| height="120px" | [[Image:Cactus (A(B)) Big.jpg|60px]]
 +
| <math>\texttt{(} a \texttt{(} b \texttt{))}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
x ~\text{implies}~ y
+
a ~\operatorname{implies}~ b
\\
+
\\[6pt]
\mathrm{If}~ x ~\text{then}~ y
+
\operatorname{if}~ a ~\operatorname{then}~ b
 
\end{matrix}</math>
 
\end{matrix}</math>
| <math>x \Rightarrow y\!</math>
+
| <math>a \Rightarrow b</math>
 
|-
 
|-
| <math>\texttt{(} x \texttt{,} y \texttt{)}\!</math>
+
| height="120px" | [[Image:Cactus (A,B) Big ISW.jpg|65px]]
 +
| <math>\texttt{(} a \texttt{,} b \texttt{)}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
x ~\text{not equal to}~ y
+
a ~\operatorname{not~equal~to}~ b
\\
+
\\[6pt]
x ~\text{exclusive or}~ y
+
a ~\operatorname{exclusive~or}~ b
 
\end{matrix}</math>
 
\end{matrix}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
x \ne y
+
a \neq b
\\
+
\\[6pt]
x + y
+
a + b
 
\end{matrix}</math>
 
\end{matrix}</math>
 
|-
 
|-
| <math>\texttt{((} x \texttt{,} y \texttt{))}\!</math>
+
| height="160px" | [[Image:Cactus ((A,B)) Big.jpg|65px]]
 +
| <math>\texttt{((} a \texttt{,} b \texttt{))}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
x ~\text{is equal to}~ y
+
a ~\operatorname{is~equal~to}~ b
\\
+
\\[6pt]
x ~\text{if and only if}~ y
+
a ~\operatorname{if~and~only~if}~ b
 
\end{matrix}</math>
 
\end{matrix}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
x = y
+
a = b
\\
+
\\[6pt]
x \Leftrightarrow y
+
a \Leftrightarrow b
 
\end{matrix}</math>
 
\end{matrix}</math>
 
|-
 
|-
| <math>\texttt{(} x \texttt{,} y \texttt{,} z \texttt{)}\!</math>
+
| height="120px" | [[Image:Cactus (A,B,C) Big.jpg|65px]]
 +
| <math>\texttt{(} a \texttt{,} b \texttt{,} c \texttt{)}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
\text{Just one of}
+
\operatorname{just~one~of}
 
\\
 
\\
x, y, z
+
a, b, c
 
\\
 
\\
\text{is false}.
+
\operatorname{is~false}.
 
\end{matrix}</math>
 
\end{matrix}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
x'y~z~ & \lor
+
& \bar{a} ~ b ~ c
 
\\
 
\\
x~y'z~ & \lor
+
\lor & a ~ \bar{b} ~ c
 
\\
 
\\
x~y~z' &
+
\lor & a ~ b ~ \bar{c}
 
\end{matrix}</math>
 
\end{matrix}</math>
 
|-
 
|-
| <math>\texttt{((} x \texttt{),(} y \texttt{),(} z \texttt{))}\!</math>
+
| height="160px" | [[Image:Cactus ((A),(B),(C)) Big.jpg|65px]]
 +
| <math>\texttt{((} a \texttt{),(} b \texttt{),(} c \texttt{))}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
\text{Just one of}
+
\operatorname{just~one~of}
\\
  −
x, y, z
  −
\\
  −
\text{is true}.
   
\\
 
\\
&
+
a, b, c
 
\\
 
\\
\text{Partition all}
+
\operatorname{is~true}.
 +
\\[6pt]
 +
\operatorname{partition~all}
 
\\
 
\\
\text{into}~ x, y, z.
+
\operatorname{into}~ a, b, c.
 
\end{matrix}</math>
 
\end{matrix}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
x~y'z' & \lor
+
& a ~ \bar{b} ~ \bar{c}
 
\\
 
\\
x'y~z' & \lor
+
\lor & \bar{a} ~ b ~ \bar{c}
 
\\
 
\\
x'y'z~ &
+
\lor & \bar{a} ~ \bar{b} ~ c
 
\end{matrix}</math>
 
\end{matrix}</math>
 
|-
 
|-
 +
| height="160px" | [[Image:Cactus (A,(B,C)) Big.jpg|90px]]
 +
| <math>\texttt{(} a \texttt{,(} b \texttt{,} c \texttt{))}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
\texttt{((} x \texttt{,} y \texttt{),} z \texttt{)}
+
\operatorname{oddly~many~of}
 
\\
 
\\
&
+
a, b, c
 
\\
 
\\
\texttt{(} x \texttt{,(} y \texttt{,} z \texttt{))}
+
\operatorname{are~true}.
\end{matrix}\!</math>
+
\end{matrix}</math>
|
  −
<math>\begin{matrix}
  −
\text{Oddly many of}
  −
\\
  −
x, y, z
  −
\\
  −
\text{are true}.
  −
\end{matrix}\!</math>
   
|
 
|
<p><math>x + y + z\!</math></p>
+
<p><math>a + b + c\!</math></p>
 
<br>
 
<br>
 
<p><math>\begin{matrix}
 
<p><math>\begin{matrix}
x~y~z~ & \lor
+
& a ~ b ~ c
 
\\
 
\\
x~y'z' & \lor
+
\lor & a ~ \bar{b} ~ \bar{c}
 
\\
 
\\
x'y~z' & \lor
+
\lor & \bar{a} ~ b ~ \bar{c}
 
\\
 
\\
x'y'z~ &
+
\lor & \bar{a} ~ \bar{b} ~ c
\end{matrix}\!</math></p>
+
\end{matrix}</math></p>
 
|-
 
|-
| <math>\texttt{(} w \texttt{,(} x \texttt{),(} y \texttt{),(} z \texttt{))}\!</math>
+
| height="160px" | [[Image:Cactus (X,(A),(B),(C)) Big.jpg|90px]]
 +
| <math>\texttt{(} x \texttt{,(} a \texttt{),(} b \texttt{),(} c \texttt{))}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
\text{Partition}~ w
+
\operatorname{partition}~ x
 
\\
 
\\
\text{into}~ x, y, z.
+
\operatorname{into}~ a, b, c.
 +
\\[6pt]
 +
\operatorname{genus}~ x ~\operatorname{comprises}
 
\\
 
\\
&
+
\operatorname{species}~ a, b, c.
\\
  −
\text{Genus}~ w ~\text{comprises}
  −
\\
  −
\text{species}~ x, y, z.
   
\end{matrix}</math>
 
\end{matrix}</math>
 
|
 
|
 
<math>\begin{matrix}
 
<math>\begin{matrix}
w'x'y'z' & \lor
+
& \bar{x} ~ \bar{a} ~ \bar{b} ~ \bar{c}
 
\\
 
\\
w~x~y'z' & \lor
+
\lor & x ~ a ~ \bar{b} ~ \bar{c}
 
\\
 
\\
w~x'y~z' & \lor
+
\lor & x ~ \bar{a} ~ b ~ \bar{c}
 
\\
 
\\
w~x'y'z~ &
+
\lor & x ~ \bar{a} ~ \bar{b} ~ c
 
\end{matrix}</math>
 
\end{matrix}</math>
 
|}
 
|}
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A sketch of this work is presented in the following series of Figures, where each logical proposition is expanded over the basic cells <math>uv, u \texttt{(} v \texttt{)}, \texttt{(} u \texttt{)} v, \texttt{(} u \texttt{)(} v \texttt{)}\!</math> of the 2-dimensional universe of discourse <math>U^\bullet = [u, v].\!</math>
 
A sketch of this work is presented in the following series of Figures, where each logical proposition is expanded over the basic cells <math>uv, u \texttt{(} v \texttt{)}, \texttt{(} u \texttt{)} v, \texttt{(} u \texttt{)(} v \texttt{)}\!</math> of the 2-dimensional universe of discourse <math>U^\bullet = [u, v].\!</math>
   −
===Computation Summary : <math>f(u, v) = \texttt{((u)(v))}</math>===
+
===Computation Summary for Logical Disjunction===
   −
The venn diagram in Figure&nbsp;1.1 shows how the proposition <math>f = \texttt{((u)(v))}</math> can be expanded over the universe of discourse <math>[u, v]\!</math> to produce a logically equivalent exclusive disjunction, namely, <math>\texttt{uv~+~u(v)~+~(u)v}.</math>
+
The venn diagram in Figure&nbsp;1.1 shows how the proposition <math>f = \texttt{((} u \texttt{)(} v \texttt{))}\!</math> can be expanded over the universe of discourse <math>[u, v]\!</math> to produce a logically equivalent exclusive disjunction, namely, <math>uv + u \texttt{(} v \texttt{)} + \texttt{(} u \texttt{)} v.\!</math>
    
{| align="center" border="0" cellpadding="10"
 
{| align="center" border="0" cellpadding="10"
Line 811: Line 807:  
|}
 
|}
   −
Figure&nbsp;1.2 expands <math>\mathrm{E}f = \texttt{((u + du)(v + dv))}</math> over <math>[u, v]\!</math> to give:
+
Figure&nbsp;1.2 expands <math>\mathrm{E}f = \texttt{((} u + \mathrm{d}u \texttt{)(} v + \mathrm{d}v \texttt{))}\!</math> over <math>[u, v]\!</math> to give:
   −
{| align="center" cellpadding="8" width="90%"
+
{| align="center" cellpadding="8"
| <math>\texttt{uv~(du~dv) ~+~ u(v)~(du (dv)) ~+~ (u)v~((du) dv) ~+~ (u)(v)~((du)(dv))}</math>
+
|
 +
<math>\begin{matrix}
 +
\mathrm{E}\texttt{((} u \texttt{)(} v \texttt{))}
 +
& = & uv \cdot \texttt{(} \mathrm{d}u ~ \mathrm{d}v \texttt{)}
 +
& + & u \texttt{(} v \texttt{)} \cdot \texttt{(} \mathrm{d}u \texttt{(} \mathrm{d}v \texttt{))}
 +
& + & \texttt{(} u \texttt{)} v \cdot \texttt{((} \mathrm{d}u \texttt{)} \mathrm{d}v \texttt{)}
 +
& + & \texttt{(} u \texttt{)(} v \texttt{)} \cdot \texttt{((} \mathrm{d}u \texttt{)(} \mathrm{d}v \texttt{))}
 +
\end{matrix}</math>
 
|}
 
|}
   Line 861: Line 864:  
|}
 
|}
   −
Figure&nbsp;1.3 expands <math>\mathrm{D}f = f + \mathrm{E}f</math> over <math>[u, v]\!</math> to produce:
+
Figure&nbsp;1.3 expands <math>\mathrm{D}f = f + \mathrm{E}f\!</math> over <math>[u, v]\!</math> to produce:
   −
{| align="center" cellpadding="8" width="90%"
+
{| align="center" cellpadding="8"
| <math>\texttt{uv~du~dv ~+~ u(v)~du(dv) ~+~ (u)v~(du)dv ~+~ (u)(v)~((du)(dv))}</math>
+
|
 +
<math>\begin{matrix}
 +
\mathrm{D}\texttt{((} u \texttt{)(} v \texttt{))}
 +
& = & uv \cdot \mathrm{d}u ~ \mathrm{d}v
 +
& + & u \texttt{(} v \texttt{)} \cdot \mathrm{d}u \texttt{(} \mathrm{d}v \texttt{)}
 +
& + & \texttt{(} u \texttt{)} v \cdot \texttt{(} \mathrm{d}u \texttt{)} \mathrm{d}v
 +
& + & \texttt{(} u \texttt{)(} v \texttt{)} \cdot \texttt{((} \mathrm{d}u \texttt{)(} \mathrm{d}v \texttt{))}
 +
\end{matrix}</math>
 
|}
 
|}
   Line 913: Line 923:  
I'll break this here in case anyone wants to try and do the work for <math>g\!</math> on their own.
 
I'll break this here in case anyone wants to try and do the work for <math>g\!</math> on their own.
   −
===Computation Summary : <math>g(u, v) = \texttt{((u,~v))}</math>===
+
===Computation Summary for Logical Equality===
   −
The venn diagram in Figure&nbsp;2.1 shows how the proposition <math>g = \texttt{((u,~v))}</math> can be expanded over the universe of discourse <math>[u, v]\!</math> to produce a logically equivalent exclusive disjunction, namely, <math>\texttt{uv ~+~ (u)(v)}.</math>
+
The venn diagram in Figure&nbsp;2.1 shows how the proposition <math>g = \texttt{((} u \texttt{,~} v \texttt{))}\!</math> can be expanded over the universe of discourse <math>[u, v]\!</math> to produce a logically equivalent exclusive disjunction, namely, <math>uv + \texttt{(} u \texttt{)(} v \texttt{)}.\!</math>
    
{| align="center" border="0" cellpadding="10"
 
{| align="center" border="0" cellpadding="10"
Line 961: Line 971:  
|}
 
|}
   −
Figure&nbsp;2.2 expands <math>\mathrm{E}g = \texttt{((u + du,~v + dv))}</math> over <math>[u, v]\!</math> to give:
+
Figure&nbsp;2.2 expands <math>\mathrm{E}g = \texttt{((} u + \mathrm{d}u \texttt{,~} v + \mathrm{d}v \texttt{))}\!</math> over <math>[u, v]\!</math> to give:
   −
{| align="center" cellpadding="8" width="90%"
+
{| align="center" cellpadding="8"
| <math>\texttt{uv~((du,~dv)) ~+~ u(v)~(du,~dv) ~+~ (u)v~(du,~dv) ~+~ (u)(v)~((du,~dv))}</math>
+
|
 +
<math>\begin{matrix}
 +
\mathrm{E}\texttt{((} u \texttt{,~} v \texttt{))}
 +
& = & uv \cdot \texttt{((} \mathrm{d}u \texttt{,~} \mathrm{d}v \texttt{))}
 +
& + & u \texttt{(} v \texttt{)} \cdot \texttt{(} \mathrm{d}u \texttt{,~} \mathrm{d}v \texttt{)}
 +
& + & \texttt{(} u \texttt{)} v \cdot \texttt{(} \mathrm{d}u \texttt{,~} \mathrm{d}v \texttt{)}
 +
& + & \texttt{(} u \texttt{)(} v \texttt{)} \cdot \texttt{((} \mathrm{d}u \texttt{,~} \mathrm{d}v \texttt{))}
 +
\end{matrix}</math>
 
|}
 
|}
   Line 1,011: Line 1,028:  
|}
 
|}
   −
Figure&nbsp;2.3 expands <math>\mathrm{D}g = g + \mathrm{E}g</math> over <math>[u, v]\!</math> to yield the form:
+
Figure&nbsp;2.3 expands <math>\mathrm{D}g = g + \mathrm{E}g\!</math> over <math>[u, v]\!</math> to yield the form:
   −
{| align="center" cellpadding="8" width="90%"
+
{| align="center" cellpadding="8"
| <math>\texttt{uv~(du,~dv) ~+~ u(v)~(du,~dv) ~+~ (u)v~(du,~dv) ~+~ (u)(v)~(du,~dv)}\!</math>
+
|
 +
<math>\begin{matrix}
 +
\mathrm{D}\texttt{((} u \texttt{,~} v \texttt{))}
 +
& = & uv \cdot \texttt{(} \mathrm{d}u \texttt{,~} \mathrm{d}v \texttt{)}
 +
& + & u \texttt{(} v \texttt{)} \cdot \texttt{(} \mathrm{d}u \texttt{,~} \mathrm{d}v \texttt{)}
 +
& + & \texttt{(} u \texttt{)} v \cdot \texttt{(} \mathrm{d}u \texttt{,~} \mathrm{d}v \texttt{)}
 +
& + & \texttt{(} u \texttt{)(} v \texttt{)} \cdot \texttt{(} \mathrm{d}u \texttt{,~} \mathrm{d}v \texttt{)}
 +
\end{matrix}</math>
 
|}
 
|}
   Line 1,082: Line 1,106:  
|
 
|
 
<math>\begin{array}{lllll}
 
<math>\begin{array}{lllll}
F & = & (f, g) & = & ( ~\texttt{((u)(v))}~ , ~\texttt{((u,~v))}~ ).
+
F
 +
& = & (f, g)
 +
& = & ( ~ \texttt{((} u \texttt{)(} v \texttt{))} ~,~ \texttt{((} u \texttt{,~} v \texttt{))} ~ )
 
\end{array}</math>
 
\end{array}</math>
 
|}
 
|}
Line 1,088: Line 1,114:  
To speed things along, I will skip a mass of motivating discussion and just exhibit the simplest form of a differential <math>\mathrm{d}F\!</math> for the current example of a logical transformation <math>F,\!</math> after which the majority of the easiest questions will have been answered in visually intuitive terms.
 
To speed things along, I will skip a mass of motivating discussion and just exhibit the simplest form of a differential <math>\mathrm{d}F\!</math> for the current example of a logical transformation <math>F,\!</math> after which the majority of the easiest questions will have been answered in visually intuitive terms.
   −
For <math>F = (f, g)\!</math> we have <math>\mathrm{d}F = (\mathrm{d}f, \mathrm{d}g),</math> and so we can proceed componentwise, patching the pieces back together at the end.
+
For <math>F = (f, g)\!</math> we have <math>\mathrm{d}F = (\mathrm{d}f, \mathrm{d}g),\!</math> and so we can proceed componentwise, patching the pieces back together at the end.
    
We have prepared the ground already by computing these terms:
 
We have prepared the ground already by computing these terms:
Line 1,095: Line 1,121:  
|
 
|
 
<math>\begin{array}{lll}
 
<math>\begin{array}{lll}
\mathrm{E}f & = & \texttt{(( u + du )( v + dv ))}
+
\mathrm{E}f & = & \texttt{((} u + \mathrm{d}u \texttt{)(} v + \mathrm{d}v \texttt{))}
\\ \\
+
\\[8pt]
\mathrm{E}g & = & \texttt{(( u + du ,~ v + dv ))}
+
\mathrm{E}g & = & \texttt{((} u + \mathrm{d}u \texttt{,~} v + \mathrm{d}v \texttt{))}
\\ \\
+
\\[8pt]
\mathrm{D}f & = & \texttt{((u)(v)) ~+~ (( u + du )( v + dv ))}
+
\mathrm{D}f & = & \texttt{((} u \texttt{)(} v \texttt{))} ~+~ \texttt{((} u + \mathrm{d}u \texttt{)(} v + \mathrm{d}v \texttt{))}
\\ \\
+
\\[8pt]
\mathrm{D}g & = & \texttt{((u,~v)) ~+~ (( u + du ,~ v + dv ))}
+
\mathrm{D}g & = & \texttt{((} u \texttt{,~} v \texttt{))} ~+~ \texttt{((} u + \mathrm{d}u \texttt{,~} v + \mathrm{d}v \texttt{))}
\end{array}\!</math>
+
\end{array}</math>
 
|}
 
|}
   −
As a matter of fact, computing the symmetric differences <math>\mathrm{D}f = f + \mathrm{E}f</math> and <math>\mathrm{D}g = g + \mathrm{E}g</math> has already taken care of the ''localizing'' part of the task by subtracting out the forms of <math>f\!</math> and <math>g\!</math> from the forms of <math>\mathrm{E}f</math> and <math>\mathrm{E}g,</math> respectively.  Thus all we have left to do is to decide what linear propositions best approximate the difference maps <math>\mathrm{D}f</math> and <math>\mathrm{D}g,</math> respectively.
+
As a matter of fact, computing the symmetric differences <math>\mathrm{D}f = f + \mathrm{E}f\!</math> and <math>\mathrm{D}g = g + \mathrm{E}g\!</math> has already taken care of the ''localizing'' part of the task by subtracting out the forms of <math>f\!</math> and <math>g\!</math> from the forms of <math>\mathrm{E}f\!</math> and <math>\mathrm{E}g,\!</math> respectively.  Thus all we have left to do is to decide what linear propositions best approximate the difference maps <math>{\mathrm{D}f}\!</math> and <math>{\mathrm{D}g},\!</math> respectively.
    
This raises the question:  What is a linear proposition?
 
This raises the question:  What is a linear proposition?
   −
The answer that makes the most sense in this context is this:  A proposition is just a boolean-valued function, so a linear proposition is a linear function into the boolean space <math>\mathbb{B}.</math>
+
The answer that makes the most sense in this context is this:  A proposition is just a boolean-valued function, so a linear proposition is a linear function into the boolean space <math>\mathbb{B}.\!</math>
   −
In particular, the linear functions that we want will be linear functions in the differential variables <math>du\!</math> and <math>dv.\!</math>
+
In particular, the linear functions that we want will be linear functions in the differential variables <math>\mathrm{d}u\!</math> and <math>\mathrm{d}v.\!</math>
   −
As it turns out, there are just four linear propositions in the associated ''differential universe'' <math>\mathrm{d}U^\bullet = [du, dv],</math> and these are the propositions that are commonly denoted:  <math>\texttt{0}, \texttt{du}, \texttt{dv}, \texttt{du + dv},</math> in other words, <math>\texttt{()}, \texttt{du}, \texttt{dv}, \texttt{(du, dv)}.</math>
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As it turns out, there are just four linear propositions in the associated ''differential universe'' <math>\mathrm{d}U^\bullet = [\mathrm{d}u, \mathrm{d}v].\!</math> These are the propositions that are commonly denoted:  <math>{0, ~\mathrm{d}u, ~\mathrm{d}v, ~\mathrm{d}u + \mathrm{d}v},\!</math> in other words<math>\texttt{(~)}, ~\mathrm{d}u, ~\mathrm{d}v, ~\texttt{(} \mathrm{d}u \texttt{,~} \mathrm{d}v \texttt{)}.\!</math>
    
==Notions of Approximation==
 
==Notions of Approximation==
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