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| 5 | <title>cmset_op.pro (SAXO Documentation Assistant)</title> |
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| 47 | <td width="10%"> |
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| 48 | <a href="cmapply.html"><img src="./../prev.gif" border="0" alt="Previous"></a></td> |
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| 49 | <td width="80%" align="center" valign="center"> |
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| 50 | <font size=-1><i>SAXO Documentation Assistant</i>: <a href="./../home.html">Overview</a></font></td> |
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| 51 | <td width="10%" align="right"> |
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| 53 | </tr> |
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| 54 | </table> |
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| 55 | |
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| 56 | |
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| 57 | <h1><font size="-2">Matrix/</font></h1> |
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| 58 | <h2>cmset_op.pro</h2> |
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| 59 | |
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| 60 | <dl> |
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| 61 | </dl> |
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| 62 | |
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| 63 | |
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| 64 | Simplified version of CMSET_OP_UNIQ which sorts, and takes the |
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| 65 | "first" value, whatever that may mean. |
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| 66 | |
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| 67 | |
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| 68 | Performs an AND, OR, or XOR operation between two sets |
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| 69 | |
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| 70 | Description: SET_OP performs three common operations between two sets. The |
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| 71 | three supported functions of OP are: |
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| 72 | |
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| 73 | OP Meaning |
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| 74 | 'AND' - to find the intersection of A and B; |
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| 75 | 'OR' - to find the union of A and B; |
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| 76 | 'XOR' - to find the those elements who are members of A or B |
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| 77 | but not both; |
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| 78 | |
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[321] | 79 | Sets as defined here is one dimensional array composed of |
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[163] | 80 | numeric or string types. Comparisons of equality between elements |
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| 81 | are done using the IDL EQ operator. |
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| 82 | |
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| 83 | The complements of either set can be taken as well, by using the |
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| 84 | NOT1 and NOT2 keywords. For example, it may be desirable to find |
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| 85 | the elements in A but not B, or B but not A (they are different!). |
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| 86 | The following IDL expressions achieve each of those effects: |
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| 87 | |
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| 88 | SET = CMSET_OP(A, 'AND', /NOT2, B) ; A but not B |
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| 89 | SET = CMSET_OP(/NOT1, A, 'AND', B) ; B but not A |
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| 90 | |
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| 91 | Note the distinction between NOT1 and NOT2. NOT1 refers to the |
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| 92 | first set (A) and NOT2 refers to the second (B). Their ordered |
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| 93 | placement in the calling sequence is entirely optional, but the |
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| 94 | above ordering makes the logical meaning explicit. |
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| 95 | |
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| 96 | NOT1 and NOT2 can only be set for the 'AND' operator, and never |
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| 97 | simultaneously. This is because the results of an operation with |
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| 98 | 'OR' or 'XOR' and any combination of NOTs -- or with 'AND' and |
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| 99 | both NOTs -- formally cannot produce a defined result. |
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| 100 | |
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| 101 | The implementation depends on the type of operands. For integer |
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| 102 | types, a fast technique using HISTOGRAM is used. However, this |
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| 103 | algorithm becomes inefficient when the dynamic range in the data |
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| 104 | is large. For those cases, and for other data types, a technique |
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| 105 | based on SORT() is used. Thus the compute time should scale |
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| 106 | roughly as (A+B)*ALOG(A+B) or better, rather than (A*B) for the |
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| 107 | brute force approach. For large arrays this is a significant |
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| 108 | benefit. |
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| 109 | |
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| 110 | |
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| 111 | |
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| 112 | |
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| 113 | |
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| 114 | <a name="#_cmset_op"></a> |
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| 115 | |
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[242] | 116 | <h2>cmset_op <font size="-1" color="#006633"> |
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[163] | 117 | Array |
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| 118 | </font></h2> |
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| 119 | |
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[290] | 120 | <p><font face="Courier"><i>result = </i>cmset_op(<i><a href="#_cmset_op_keyword_a">a</a>, <a href="#_cmset_op_keyword_op0">op0</a>, <a href="#_cmset_op_keyword_b">b</a></i>, <a href="#_cmset_op_keyword_NOT1">NOT1</a>=<i>NOT1</i>, <a href="#_cmset_op_keyword_NOT2">NOT2</a>=<i>NOT2</i>, <a href="#_cmset_op_keyword_COUNT">COUNT</a>=<i>COUNT</i>, <a href="#_cmset_op_keyword_EMPTY1">EMPTY1</a>=<i>EMPTY1</i>, <a href="#_cmset_op_keyword_EMPTY2">EMPTY2</a>=<i>EMPTY2</i>, <a href="#_cmset_op_keyword_MAXARRAY">MAXARRAY</a>=<i>MAXARRAY</i>, <a href="#_cmset_op_keyword_INDEX">INDEX</a>=<i>INDEX</i>)</font></p> |
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[163] | 121 | |
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| 122 | |
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| 123 | |
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| 124 | |
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| 125 | <h3>Return value</h3> |
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| 126 | The resulting set as a one-dimensional array. The set may be |
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| 127 | represented by either an array of data values (default), or an |
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| 128 | array of indexes (if INDEX is set). Duplicate elements, if any, |
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| 129 | are removed, and element order may not be preserved. |
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| 130 | |
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| 131 | The empty set is represented as a return value of -1L, and COUNT |
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| 132 | is set to zero. Note that the only way to recognize the empty set |
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| 133 | is to examine COUNT. |
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| 134 | |
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| 135 | SEE ALSO: |
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| 136 | |
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| 137 | SET_UTILS.PRO by RSI |
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| 138 | |
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| 139 | |
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| 140 | |
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| 141 | <h3>Parameters</h3> |
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| 142 | |
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| 143 | |
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| 144 | <a name="#_cmset_op_keyword_a"></a> |
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| 145 | <h4>a |
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| 146 | <font size="-1" color="#006633">in</font> |
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| 147 | |
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| 148 | |
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| 149 | <font size="-1" color="#006633">required</font> |
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| 150 | |
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| 151 | |
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| 152 | |
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| 153 | |
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| 154 | </h4> |
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| 155 | |
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| 156 | |
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| 157 | The two sets to be operated on. A one dimensional array of |
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| 158 | either numeric or string type. A and B must be of the same |
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| 159 | type. Empty sets are permitted, and are either represented |
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| 160 | as an undefined variable, or by setting EMPTY1 or EMPTY2. |
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| 161 | |
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| 162 | |
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| 163 | |
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| 164 | <a name="#_cmset_op_keyword_op0"></a> |
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| 165 | <h4>op0 |
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| 166 | <font size="-1" color="#006633">in</font> |
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| 167 | |
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| 168 | |
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| 169 | <font size="-1" color="#006633">required</font> |
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| 170 | |
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| 171 | <font size="-1" color="#006633">type:</font> <font size="-1" color="#006633"><i>string</i></font> |
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| 172 | |
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| 173 | |
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| 174 | </h4> |
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| 175 | |
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| 176 | |
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| 177 | a string, the operation to be performed. Must be one of |
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| 178 | 'AND', 'OR' or 'XOR' (lower or mixed case is permitted). |
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| 179 | Other operations will cause an error message to be produced. |
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| 180 | |
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| 181 | |
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| 182 | |
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| 183 | <a name="#_cmset_op_keyword_b"></a> |
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| 184 | <h4>b |
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| 185 | <font size="-1" color="#006633">in</font> |
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| 186 | |
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| 187 | |
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| 188 | <font size="-1" color="#006633">required</font> |
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| 189 | |
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| 190 | |
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| 191 | |
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| 192 | |
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| 193 | </h4> |
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| 194 | |
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| 195 | |
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| 196 | See A |
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| 197 | |
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| 198 | |
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| 199 | |
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| 200 | |
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| 201 | |
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| 202 | <h3>Keywords</h3> |
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| 203 | |
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| 204 | |
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[290] | 205 | <a name="#_cmset_op_keyword_NOT1"></a> |
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| 206 | <h4>NOT1 |
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[163] | 207 | |
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| 208 | |
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| 209 | |
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| 210 | |
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| 211 | |
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| 212 | |
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| 213 | |
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| 214 | |
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| 215 | </h4> |
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| 216 | |
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| 217 | |
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| 218 | If set and OP is 'AND', then the complement of A (for |
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| 219 | NOT1) or B (for NOT2) will be used in the operation. |
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| 220 | NOT1 and NOT2 cannot be set simultaneously. |
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| 221 | |
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| 222 | |
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[290] | 223 | <a name="#_cmset_op_keyword_NOT2"></a> |
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| 224 | <h4>NOT2 |
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[163] | 225 | |
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| 226 | |
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| 227 | |
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| 228 | |
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| 229 | |
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| 230 | |
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| 231 | |
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| 232 | |
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| 233 | </h4> |
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| 234 | |
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| 235 | |
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| 236 | See NOT1 |
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| 237 | |
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| 238 | |
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[290] | 239 | <a name="#_cmset_op_keyword_COUNT"></a> |
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| 240 | <h4>COUNT |
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[163] | 241 | |
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| 242 | |
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| 243 | |
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| 244 | |
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| 245 | |
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| 246 | |
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| 247 | |
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| 248 | |
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| 249 | </h4> |
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| 250 | |
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| 251 | |
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| 252 | upon return, the number of elements in the result set. |
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| 253 | This is only important when the result set is the empty |
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| 254 | set, in which case COUNT is set to zero. |
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| 255 | |
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| 256 | |
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[290] | 257 | <a name="#_cmset_op_keyword_EMPTY1"></a> |
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| 258 | <h4>EMPTY1 |
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[163] | 259 | |
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| 260 | |
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| 261 | |
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| 262 | |
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| 263 | |
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| 264 | |
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| 265 | |
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| 266 | |
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| 267 | </h4> |
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| 268 | |
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| 269 | |
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| 270 | If set, then A (for EMPTY1) or B (for EMPTY2) are |
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| 271 | assumed to be the empty set. The actual values |
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| 272 | passed as A or B are then ignored. |
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| 273 | |
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| 274 | |
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[290] | 275 | <a name="#_cmset_op_keyword_EMPTY2"></a> |
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| 276 | <h4>EMPTY2 |
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[163] | 277 | |
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| 278 | |
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| 279 | |
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| 280 | |
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| 281 | |
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| 282 | |
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| 283 | |
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| 284 | |
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| 285 | </h4> |
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| 286 | |
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| 287 | |
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| 288 | See EMPTY1 |
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| 289 | |
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| 290 | |
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[290] | 291 | <a name="#_cmset_op_keyword_MAXARRAY"></a> |
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| 292 | <h4>MAXARRAY |
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[163] | 293 | |
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| 294 | |
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| 295 | |
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| 296 | |
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| 297 | |
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| 298 | |
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| 299 | |
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| 300 | |
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| 301 | </h4> |
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| 302 | |
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| 303 | |
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| 304 | |
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[290] | 305 | <a name="#_cmset_op_keyword_INDEX"></a> |
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| 306 | <h4>INDEX |
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[163] | 307 | |
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| 308 | |
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| 309 | |
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| 310 | |
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| 311 | |
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| 312 | |
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| 313 | |
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| 314 | |
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| 315 | </h4> |
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| 316 | |
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| 317 | |
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| 318 | if set, then return a list of indexes instead of the array |
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| 319 | values themselves. The "slower" set operations are always |
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| 320 | performed in this case. |
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| 321 | |
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| 322 | The indexes refer to the *combined* array [A,B]. To |
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| 323 | clarify, in the following call: I = CMSET_OP(..., /INDEX); |
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| 324 | returned values from 0 to NA-1 refer to A[I], and values |
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| 325 | from NA to NA+NB-1 refer to B[I-NA]. |
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| 326 | |
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| 327 | |
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| 328 | |
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| 329 | |
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[234] | 330 | <h3>Examples</h3><pre> |
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[163] | 331 | Utility function, similar to UNIQ, but allowing choice of taking |
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| 332 | first or last unique element, or non-unique elements. |
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| 333 | Unfortunately this doesn't work because of implementation dependent |
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| 334 | versions of the SORT() function. |
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| 335 | |
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| 336 | function cmset_op_uniq, a, first=first, non=non, count=ct, sort=sortit |
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| 337 | if n_elements(a) LE 1 then return, 0L |
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| 338 | sh = (2L*keyword_set(first)-1L)*(-2L*keyword_set(non)+1) |
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| 339 | |
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| 340 | if keyword_set(sortit) then begin |
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| 341 | ;; Sort it manually |
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| 342 | ii = sort(a) & b = a[ii] |
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| 343 | if keyword_set(non) then wh = where(b EQ shift(b, sh), ct) $ |
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| 344 | else wh = where(b NE shift(b, sh), ct) |
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| 345 | if ct GT 0 then return, ii[wh] |
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| 346 | endif else begin |
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| 347 | ;; Use the user's values directly |
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| 348 | if keyword_set(non) then wh = where(a EQ shift(a, sh), ct) $ |
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| 349 | else wh = where(a NE shift(a, sh), ct) |
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| 350 | if ct GT 0 then return, wh |
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| 351 | endelse |
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| 352 | |
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| 353 | if keyword_set(first) then return, 0L else return, n_elements(a)-1 |
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| 354 | end |
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| 355 | |
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| 356 | Simplified version of CMSET_OP_UNIQ which sorts, and takes the |
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| 357 | "first" value, whatever that may mean. |
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| 358 | |
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[234] | 359 | </pre><h3>Version history</h3> |
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[163] | 360 | |
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[242] | 361 | <h4>Version</h4> |
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[402] | 362 | $Id: cmset_op.pro 372 2008-08-08 12:31:53Z pinsard $ |
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[163] | 363 | |
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[242] | 364 | <h4>History</h4> |
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| 365 | Written, CM, 23 Feb 2000 |
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[163] | 366 | Added empty set capability, CM, 25 Feb 2000 |
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| 367 | Documentation clarification, CM 02 Mar 2000 |
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| 368 | Incompatible but more consistent reworking of EMPTY keywords, CM, |
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| 369 | 04 Mar 2000 |
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| 370 | Minor documentation clarifications, CM, 26 Mar 2000 |
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| 371 | Corrected bug in empty_arg special case, CM 06 Apr 2000 |
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| 372 | Add INDEX keyword, CM 31 Jul 2000 |
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| 373 | Clarify INDEX keyword documentation, CM 06 Sep 2000 |
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| 374 | Made INDEX keyword always force SLOW_SET_OP, CM 06 Sep 2000 |
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| 375 | Added CMSET_OP_UNIQ, and ability to select FIRST_UNIQUE or |
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| 376 | LAST_UNIQUE values, CM, 18 Sep 2000 |
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| 377 | Removed FIRST_UNIQUE and LAST_UNIQUE, and streamlined |
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| 378 | CMSET_OP_UNIQ until problems with SORT can be understood, CM, 20 |
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| 379 | Sep 2000 (thanks to Ben Tupper) |
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| 380 | Still trying to get documentation of INDEX and NOT right, CM, 28 |
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| 381 | Sep 2000 (no code changes) |
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| 382 | Correct bug for AND case, when input sets A and B each only have |
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| 383 | one unique value, and the values are equal. CM, 04 Mar 2004 |
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| 384 | (thanks to James B. jbattat at cfa dot harvard dot edu) |
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| 385 | Add support for the cases where the input data types are mixed, |
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| 386 | but still compatible; also, attempt to return the same data |
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| 387 | type that was passed in; CM, 05 Feb 2005 |
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| 388 | Fix bug in type checking (thanks to "marit"), CM, 10 Dec 2005 |
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| 389 | Work around a stupidity in the built-in IDL HISTOGRAM routine, |
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| 390 | which tries to "help" you by restricting the MIN/MAX to the |
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| 391 | range of the input variable (thanks to Will Maddox), CM, 16 Jan 2006 |
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| 392 | |
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| 393 | Author: Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770 |
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| 394 | craigm@lheamail.gsfc.nasa.gov |
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| 412 | <font size="-3"><p> </p></font> |
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| 413 | <hr size="1" color="#CCCCCC"/> |
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[187] | 418 | <p><font color="gray" size="-3"> Produced by IDLdoc 2.0.</font></p> |
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[163] | 419 | |
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| 420 | </body> |
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[249] | 421 | </html> |
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