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  terminating condition for iterators

  Posted by lestat-jin on July 19, 2024 at 3:21 pm

  not sure why the below does not work as it keeps causing crash in Jupyter Notebook?

  {8>count x}{x,sum -2#x}\[0 1]

  I understand the condition to terminate iteration can be placed inside function input, e.g. f[{condition};input] or {condition}f[input], for example this works as given in the notebook : {1000 > max x}{(+)prior x,0}\ 1

  in general what is recommended ways to write conditions for terminating the “loop”/iteration ?

  Thanks,

  
  

  

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  lestat-jin replied 4 months ago 2 Members · 2 Replies
• 2 Replies

• 

  megan_mcp

  Administrator

  July 22, 2024 at 3:06 pm

  Hi @lestat-jin

  The correct way to execute your answer would be to remove the square brackets:

  {8>count x}{x,sum -2#x}\0 1
  

  This is because we are looking for the dyadic form of the scan adverb ‘x f\y’. Which if I use a parse tree to explain, would look like this:

  q)-5!"{8>count x}{x,sum -2#x}\\0 1" / the correct version
  (\;{x,sum -2#x})       
  {8>count x}            
  0 1                    
  

  However if you use square brackets after scan, it forces it into monadic scan form, ‘x[f\y]’:

  q)-5!"{8>count x}{x,sum -2#x}\\[0 1]"
  {8>count x}
  ((\;{x,sum -2#x});0 1)
  

  If you have any questions on this, please let me know!

  Thanks,

  Megan

  • 

    lestat-jin

    Member

    July 23, 2024 at 3:50 pm

    Thanks a lot. could you explain why dyadic function is expected here? what is the f in “x f\ y” here? the {8>count x}{x,sum -2#x}\0 1 only takes one argument which is x…

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