What does the question mark operator mean in Ruby

Question

What is the purpose of the question mark operator in Ruby   Sometimes it appears like this   assert  product valid    sometimes it s in an if construct

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It s a convention in Ruby that methods that return boolean values end in a question mark  There s no more significance to it than that

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It is a code style convention  it indicates that a method returns a boolean value   The question mark is a valid character at the end of a method name

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I believe it s just a convention for things that are boolean   A bit like saying  IsValid

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In your example  product valid    Is actually a function call and calls a function named valid   Certain types of  test for condition  boolean functions have a question mark as part of the function name by convention

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It s also a common convention to use with the first argument of the test method from Kernel test  irb main  001 0 gt  test  d    dev    directory exists    gt  true irb main  002 0 gt  test  -    etc hosts     etc hosts    are the files identical   gt  true   as seen in this question here

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It may be worth pointing out that  s are only allowed in method names  not variables  In the process of learning Ruby  I assumed that   designated a boolean return type so I tried adding them to flag variables  leading to errors  This led to me erroneously believing for a while that there was some special syntax involving  s   Relevant  Why can  39 t a variable name end with     while a method name can

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In your example it s just part of the method name  In Ruby you can also use exclamation points in method names    Another example of question marks in Ruby would be the ternary operator   customerName     Fred     Hello Fred     Who are you

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Also note   along with a character  will return the ASCII character code for A  For example    F     gt  will return 70   Alternately in ruby 1 8 you can do    F  0    or in ruby 1 9    F  ord   Also notice that  F will return the string  F   so in order to make the code shorter  you can also use  F ord in Ruby 1 9 to get the same result as  F  ord

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It s also used in regular expressions  meaning  at most one repetition of the preceding character   for example the regular expression  hey    matches with the strings  he  and  hey

[ruby] What does the question mark operator mean in Ruby?

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