.. _merge-command-label:

=================
MERGE Command
=================

Material prepared from `M Programming Book`_ (Page 148) [WALTERS1997]_ and `GT.M Programmer's Guide`_

MERGE
######

The MERGE command copies a variable and all its descendants into another variable.


Command
-------

    **M[ERGE]** variable1=variable2

Copies variable2 and all its descendants into variable1

Example
-------

Populate one variable with a couple of descendants
::

    SET A="Yankees"
    SET A(1)="Monday"
    SET A(2)="Thursday"

Populate another variable with a couple of descendants
::

    SET B="Red Sox"
    SET B(3)="Saturday"
    SET B(4)="Sunday"


Review their content
::

    ZWRITE A

Will print out
::

    A="Yankees"
    A(1)="Monday"
    A(2)="Thursday"

while
::

    ZWRITE B

Will print out
::

    B="Red Sox"
    B(3)="Saturday"
    B(4)="Sunday"

Then, invoking the MERGE command will merge the two variables.
::

    MERGE A=B

and a call to ZWRITE
::

   ZWRITE A

Will print out
::

     A="Red Sox"
     A(1)="Monday"
     A(2)="Thursday"
     A(3)="Saturday"
     A(4)="Sunday"


Related
#######

*  :ref:`set-command-label`


References
##########

`MERGE page at GT.M Programmer's Guide`_

.. _M Programming book: http://books.google.com/books?id=jo8_Mtmp30kC&printsec=frontcover&dq=M+Programming&hl=en&sa=X&ei=2mktT--GHajw0gHnkKWUCw&ved=0CDIQ6AEwAA#v=onepage&q=M%20Programming&f=false
.. _GT.M Programmer's Guide: http://tinco.pair.com/bhaskar/gtm/doc/books/pg/UNIX_manual/index.html
.. _MERGE page at GT.M Programmer's Guide: http://tinco.pair.com/bhaskar/gtm/doc/books/pg/UNIX_manual/ch06s15.html