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| 55 | <H2><A NAME="SECTION007260000000000000000"></A><A NAME="dict"></A> |
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| 57 | 5.2.6 Dictionary displays |
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| 59 | <a id='l2h-352' xml:id='l2h-352'></a> |
| 60 | <P> |
| 61 | A dictionary display is a possibly empty series of key/datum pairs |
| 62 | enclosed in curly braces: |
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| 64 | |
| 65 | <P> |
| 66 | <dl><dd class="grammar"> |
| 67 | <div class="productions"> |
| 68 | <table> |
| 69 | <tr> |
| 70 | <td><a id='tok-dict_display' xml:id='tok-dict_display'>dict_display</a></td> |
| 71 | <td>::=</td> |
| 72 | <td>"{" [<a class='grammartoken' href="dict.html#tok-key_datum_list">key_datum_list</a>] "}"</td></tr> |
| 73 | <tr> |
| 74 | <td><a id='tok-key_datum_list' xml:id='tok-key_datum_list'>key_datum_list</a></td> |
| 75 | <td>::=</td> |
| 76 | <td><a class='grammartoken' href="dict.html#tok-key_datum">key_datum</a> ("," <a class='grammartoken' href="dict.html#tok-key_datum">key_datum</a>)* [","]</td></tr> |
| 77 | <tr> |
| 78 | <td><a id='tok-key_datum' xml:id='tok-key_datum'>key_datum</a></td> |
| 79 | <td>::=</td> |
| 80 | <td><a class='grammartoken' href="Booleans.html#tok-expression">expression</a> ":" <a class='grammartoken' href="Booleans.html#tok-expression">expression</a></td></tr> |
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| 83 | <a class="grammar-footer" |
| 84 | href="grammar.txt" type="text/plain" |
| 85 | >Download entire grammar as text.</a> |
| 86 | </dd></dl> |
| 87 | |
| 88 | <P> |
| 89 | A dictionary display yields a new dictionary object. |
| 90 | <a id='l2h-353' xml:id='l2h-353'></a> |
| 91 | <P> |
| 92 | The key/datum pairs are evaluated from left to right to define the |
| 93 | entries of the dictionary: each key object is used as a key into the |
| 94 | dictionary to store the corresponding datum. |
| 95 | |
| 96 | <P> |
| 97 | Restrictions on the types of the key values are listed earlier in |
| 98 | section <A href="types.html#types">3.2</A>. (To summarize, the key type should be hashable, |
| 99 | which excludes all mutable objects.) Clashes between duplicate keys |
| 100 | are not detected; the last datum (textually rightmost in the display) |
| 101 | stored for a given key value prevails. |
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| 139 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> |
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