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Home Forums KX Academy What is the purpose of the underscore in this line of u.q

  • What is the purpose of the underscore in this line of u.q

    Posted by mannix on March 13, 2022 at 12:00 am

    In the u.q file of the following set up, what is the purpose of the underscore here, (It doesnt appear to me to be cut or drop)

    del:{w[x]_:w[x;;0]?y};.z.pc:{del[;x]each t};

    mannix replied 9 months, 3 weeks ago 2 Members · 1 Reply
  • 1 Reply
  • pmallon

    Member
    March 13, 2022 at 12:00 am

    Hi,

    it is drop in place to modify the dictionary w of table subscriptions. It is checking the list of subs for table x, for handle y, if there is an item its dropped from the list and w[x] is updated.

    section at the bottom here on drop in place:

    Drop in place

    Assign through Drop to delete in place.

    q)show d:`a`b`c`x!(1;2 3;4;5) 
    
    a| 1 
    b| 2 3 
    c| 4 
    x| 5 
    
    q)d _:`x 
    q)d 
    a| 1 
    b| 2 3 
    c| 4

    Hope that helps, if not let me know.

     

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