manual:chapter6:lists:cmd_map [newRPL User Manual]

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==== MAP ====
<callout type="primary" color="" icon="fa fa-book" title="Synopsis">
----
Do a procedure on each element of a list, recursively
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<callout color="green" icon="fa fa-indent" title="Stack Diagram">
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^  __Input Stack__  ^^  ^  __Output Stack__  ^
|  **L<sub>data</sub>**  |  **P<sub>exec</sub>**  |  **→**  |  **L<sub>data-upd</sub>**  |
|  **L<sub>data</sub>**  |  **N<sub>exec</sub>**  |  **→**  |  **L<sub>data-upd</sub>**  |
|  //Level 2//  |  //Level 1//  |  //→//  |  //Level 1//  |

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| **Keyword type**  | [[manual:chapter5:basics#commands|Command]]  ||
| **Parallel list processing capabilities**  | [[manual:chapter5:listproc#group-2commands-that-must-use-dolist-to-parallel-process|Group 2]]  | //Commands that must use //''[[manual:chapter6:lists:cmd_cmddolist|DOLIST]]''// to parallel process//  |
| **Affected by flags**  | //None//  ||














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<callout color="orangered" icon="fa fa-comment" title="Description">
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The ''MAP'' command ''[[manual:chapter6:operators:cmd_ovr_eval|EVAL]]''uates a specified program (or a variable which contains one) to a list of objects or values. If one of the objects is a list, ''MAP'' will apply the program recursively to the items in the inner list.\\
\\
''MAP'' is nominally designed for **P<sub>exec</sub>** (or **N<sub>exec</sub>**) __requiring one argument and returning one result__.
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<callout type="success" icon="true" title="Compatibility">
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''MAP'' is fully equivalent to its **userRPL** counterpart.
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<callout type="info" icon="true" title="Usage">
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**__Input__**
<code>
4:                                      
3:                                      
2:                       { 1 2 { X Y } }
1:                               « 2 * »
…………………………………………………………………………………………………………
MAP                                     
</code>
\\
**__Output__**
<code>
4:                                      
3:                                      
2:                                      
1:               { 2 4 { 'X*2' 'Y*2' } }
…………………………………………………………………………………………………………
                                        
</code>
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<callout color="darkgray" icon="fa fa-hand-o-right" title="Related Commands">
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