projects / OpenSPARC-T2-SAM / blame
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| 53 | <H2><A NAME="SECTION004240000000000000000"> | |
| 54 | 2.2.4 Object Comparison</A> | |
| 55 | </H2> | |
| 56 | ||
| 57 | <P> | |
| 58 | <div class="verbatim"><pre> | |
| 59 | cmpfunc tp_compare; | |
| 60 | </pre></div> | |
| 61 | ||
| 62 | <P> | |
| 63 | The <tt class="member">tp_compare</tt> handler is called when comparisons are needed | |
| 64 | and the object does not implement the specific rich comparison method | |
| 65 | which matches the requested comparison. (It is always used if defined | |
| 66 | and the <tt class="cfunction">PyObject_Compare()</tt> or <tt class="cfunction">PyObject_Cmp()</tt> | |
| 67 | functions are used, or if <tt class="function">cmp()</tt> is used from Python.) | |
| 68 | It is analogous to the <tt class="method">__cmp__()</tt> method. This function | |
| 69 | should return <code>-1</code> if <var>obj1</var> is less than | |
| 70 | <var>obj2</var>, <code>0</code> if they are equal, and <code>1</code> if | |
| 71 | <var>obj1</var> is greater than | |
| 72 | <var>obj2</var>. | |
| 73 | (It was previously allowed to return arbitrary negative or positive | |
| 74 | integers for less than and greater than, respectively; as of Python | |
| 75 | 2.2, this is no longer allowed. In the future, other return values | |
| 76 | may be assigned a different meaning.) | |
| 77 | ||
| 78 | <P> | |
| 79 | A <tt class="member">tp_compare</tt> handler may raise an exception. In this case it | |
| 80 | should return a negative value. The caller has to test for the | |
| 81 | exception using <tt class="cfunction">PyErr_Occurred()</tt>. | |
| 82 | ||
| 83 | <P> | |
| 84 | Here is a sample implementation: | |
| 85 | ||
| 86 | <P> | |
| 87 | <div class="verbatim"><pre> | |
| 88 | static int | |
| 89 | newdatatype_compare(newdatatypeobject * obj1, newdatatypeobject * obj2) | |
| 90 | { | |
| 91 | long result; | |
| 92 | ||
| 93 | if (obj1->obj_UnderlyingDatatypePtr->size < | |
| 94 | obj2->obj_UnderlyingDatatypePtr->size) { | |
| 95 | result = -1; | |
| 96 | } | |
| 97 | else if (obj1->obj_UnderlyingDatatypePtr->size > | |
| 98 | obj2->obj_UnderlyingDatatypePtr->size) { | |
| 99 | result = 1; | |
| 100 | } | |
| 101 | else { | |
| 102 | result = 0; | |
| 103 | } | |
| 104 | return result; | |
| 105 | } | |
| 106 | </pre></div> | |
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| 143 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
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