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<pre>
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(NB. I will need to figure out what I meant by the following definitions.)
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These definitions can be made a little more succinct by
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defining the following sorts of generic operators on strings:
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These definitions can be made a little more succinct by defining the following sorts of generic operators on strings:
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<ol style="list-style-type:decimal">
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<li>The ''concatenation'' <math>\operatorname{Conc}^k</math> of the <math>k\!</math> strings <math>s_j, j = 1 \ldots k,\!</math> is defined recursively as follows:</li>
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<ol style="list-style-type:lower-alpha">
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<li><math>\operatorname{Conc}^1_j s_j \ = \ s_1.</math></li>
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<li><p>For <math>k > 1,\!</math></p>
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1. The "concatenation" Conc^k of the k strings z_j,
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<p><math>\operatorname{Conc}^k_j s_j \ = \ (\operatorname{Conc}^{k-1}_j s_j) \cdot s_k.</math></p></li>
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for j = 1 to k, is defined recursively as follows:
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a. Conc^1_j z_j = z_1.
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</ol>
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b. For k > 1,
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<li>The ''surcatenation'' <math>\operatorname{Surc}^k</math> of the <math>k\!</math> strings <math>s_j, j = 1 \ldots k,\!</math> is defined recursively as follows:</li>
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Conc^k_j z_j = (Conc^(k-1)_j z_j) · z_k.
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<ol style="list-style-type:lower-alpha">
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2. The "surcatenation" Surc^k of the k strings z_j,
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<li><math>\operatorname{Surc}^1_j s_j \ = \ ^{\backprime\backprime} \, \operatorname{(} \, ^{\prime\prime} \, \cdot s_1 \cdot \, ^{\backprime\backprime} \, \operatorname{)} \, ^{\prime\prime}.</math></li>
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for j = 1 to k, is defined recursively as follows:
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a. Surc^1_j z_j = "-(" · z_1 · ")-".
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<li><p>For <math>k > 1,\!</math></p>
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b. For k > 1,
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<p><math>\operatorname{Surc}^k_j s_j \ = \ (\operatorname{Surc}^{k-1}_j s_j) \cdot \, (^{\backprime\backprime} \, \operatorname{)} \, ^{\prime\prime})^{-1} \cdot \, ^{\backprime\backprime} \, \operatorname{,} \, ^{\prime\prime} \, \cdot s_k \cdot \, ^{\backprime\backprime} \, \operatorname{)} \, ^{\prime\prime}.</math></p></li>
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Surc^k_j z_j = (Surc^(k-1)_j z_j) · ")-"^(-1) · "," · z_k · ")-".
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</ol></ol>
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<pre>
The definitions of these syntactic operations can now be organized in a slightly
The definitions of these syntactic operations can now be organized in a slightly
better fashion, for both conceptual and computational purposes, by making a few
better fashion, for both conceptual and computational purposes, by making a few