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| The first step is to define two sets of basic operations on strings of <math>\mathfrak{A}^*.</math> | | The first step is to define two sets of basic operations on strings of <math>\mathfrak{A}^*.</math> |
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| + | {| align="center" cellpadding="8" width="90%" |
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| + | | valign="top" | 1. |
| + | | The ''concatenation'' of one string <math>s_1\!</math> is just the string <math>s_1.\!</math> |
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| + | | The ''concatenation'' of two strings <math>s_1, s_2\!</math> is the string <math>s_1 \cdot s_2.\!</math> |
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| + | | The ''concatenation'' of the <math>k\!</math> strings <math>s_j,\!</math> for <math>j = 1 \ldots k,\!</math> is the string of the form <math>s_1 \cdot \ldots \cdot s_k.\!</math> |
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| + | | valign="top" | 2. |
| + | | The ''surcatenation'' of one string <math>s_1\!</math> is the string <math>^{\backprime\backprime} \, \operatorname{(} \, ^{\prime\prime} \, \cdot s_1 \cdot \, ^{\backprime\backprime} \, \operatorname{)} \, ^{\prime\prime}.</math> |
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| + | | The ''surcatenation'' of two strings <math>s_1, s_2\!</math> is <math>^{\backprime\backprime} \, \operatorname{(} \, ^{\prime\prime} \, \cdot s_1 \cdot \, ^{\backprime\backprime} \, \operatorname{,} \, ^{\prime\prime} \, \cdot s_2 \cdot \, ^{\backprime\backprime} \, \operatorname{)} \, ^{\prime\prime}.</math> |
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| + | | The ''surcatenation'' of <math>k\!</math> strings <math>s_j,\!</math> for <math>j\!</math> = 1 to <math>k,\!</math> is the string of the form <math>^{\backprime\backprime} \, \operatorname{(} \, ^{\prime\prime} \, \cdot s_1 \cdot \, ^{\backprime\backprime} \, \operatorname{,} \, ^{\prime\prime} \, \cdot \ldots \cdot \, ^{\backprime\backprime} \, \operatorname{,} \, ^{\prime\prime} \, s_k \cdot \, ^{\backprime\backprime} \, \operatorname{)} \, ^{\prime\prime}.</math> |
| + | |} |
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| <pre> | | <pre> |
− | 1. The "concatenation" of one string z_1 is just the string z_1.
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− | The "concatenation" of two strings z_1, z_2 is the string z_1 · z_2.
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− | The "concatenation" of the k strings z_j, for j = 1 to k,
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− | is the string of the form z_1 · ... · z_k.
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− | 2. The "surcatenation" of one string z_1 is the string "-(" · z_1 · ")-".
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− | The "surcatenation" of two strings z_1, z_2 is "-(" · z_1 · "," · z_2 · ")-".
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− | The "surcatenation" of k strings z_j, for j = 1 to k,
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− | is the string of the form "-(" · z_1 · "," · ... · "," · z_k · ")-".
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| These definitions can be made a little more succinct by | | These definitions can be made a little more succinct by |
| defining the following sorts of generic operators on strings: | | defining the following sorts of generic operators on strings: |