perl - How does the grep operator work? -


I have an array and a hash. I want to match the keys of the head with the key of hash.

I got an expression to fix all the keys matching the array. It works, but I'm not sure I understood how it works. Can you explain what happens after grep

array @text and hash % sys already Is defined only. 

  My @new_array = grep {$ sys {$ _} is present? $ sys {$ _}: 0} @text;    
 
 
 The code you got is more complex This could be / *:  
  My @new_array = grep {$ sys {$ _}} @text; The   
  grep  function processes a list - the contents of the  @text  array - in a new list containing only the element Where the expression in the middle evaluates a true value, the default value is set to every list item in exchange for the expression list content so that the default value is  $ _ .  
 In your example expression, a threesome operator ?  which evaluates the item before :  If the first part is true or the value after it is incorrect, in your case, it checks whether each key is % sys  is in hash, and hash evaluates a lookup of entry if it exists, or 0 (a wrong value) if it is not functionally within a  grep  Should be due to  $ sys {$ _}  because  undef  is that you have a non-denominator Key is also wrong. However, there is a caveat - if % sys  was tied to a pearl class and some hash functions were overridden, Different hash methods are called for  existing  and hash lookups. Therefore there can be a difference in performance or behavior in that scenario.

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