==== STREAM ====
<callout type="primary" color="" icon="fa fa-book" title="Synopsis">
----
Assemble a list from results of sequential procedure
</callout>

<callout color="green" icon="fa fa-indent" title="Stack Diagram">
----
^  __Input Stack__  ^^  ^  __Output Stack__  ^
|  **L<sub>data</sub>**  |  **P<sub>exec</sub>**  |  **→**  |  **O<sub>result</sub>**  |
|  **L<sub>data</sub>**  |  **N<sub>exec</sub>**  |  **→**  |  **O<sub>result</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//  ||














</callout>

<callout color="orangered" icon="fa fa-comment" title="Description">
----
The ''STREAM'' command moves the first two elements from **L<sub>data</sub>** onto the stack, ''[[manual:chapter6:operators:cmd_ovr_eval|EVAL]]''uating a program or an identifier. Then moves the next element (if any) onto the stack, and ''[[manual:chapter6:operators:cmd_ovr_eval|EVAL]]''uates **P<sub>exec</sub>** (or **N<sub>exec</sub>**) again using the previous result and the new element. Repeats this until **L<sub>data</sub>** is exhausted, and returns the final result.
\\
\\
''STREAM'' is nominally designed for **P<sub>exec</sub>** (or **N<sub>exec</sub>**) __requiring two arguments and returning one result__.
</callout>

<callout type="warning" icon="true" title="Compatibility">
----
''STREAM'' is not fully equivalent to its **userRPL** counterpart.

In particular:

  * the program launched by ''STREAM'' operates in a protected stack environment: no elements present on the stack before ''STREAM'' is launched can be reached or altered.
</callout>

<callout type="info" icon="true" title="Usage">
----
**__Input__**
<code>
4:                                      
3:                                      
2:                   { "A" "B" "C" "D" }
1:                            « SWAP + »
…………………………………………………………………………………………………………
STREAM                                  
</code>
\\
**__Output__**
<code>
4:                                      
3:                                      
2:                                      
1:                                "DCBA"
…………………………………………………………………………………………………………
                                        
</code>
</callout>

<callout color="darkgray" icon="fa fa-hand-o-right" title="Related Commands">
----
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</callout>