Difference between and and in Ruby

Question

What is the difference between the  amp  amp  and and operators in Ruby

User · Answer

and has lower precedence  mostly we use it as a control-flow modifier such as if   next if widget   widgets pop   becomes  widget   widgets pop and next   For or   raise  Not ready   unless ready to rock    becomes  ready to rock  or raise  Not ready     I prefer to use if but not and  because if is more intelligible  so I just ignore and and or   Refer to  Using    and    and    or    in Ruby  for more information

User · Answer

I don t know if this is Ruby intention or if this is a bug but try this code below  This code was run on Ruby version 2 5 1 and was on a Linux system   puts 1  gt  -1 and 257  lt  256     gt  false  puts 1  gt  -1  amp  amp  257  lt  256     gt  true

User · Answer

and has lower precedence than  amp  amp    But for an unassuming user  problems might occur if it is used along with other operators  whose precedence are in between  for example  the assignment operator   def happy    true  end def know it    true  end  todo   happy   amp  amp  know it     Clap your hands     Do Nothing   todo     gt   Clap your hands   todo   happy  and know it     Clap your hands     Do Nothing   todo     gt  true

User · Answer

and is the same as  amp  amp  but with lower precedence  They both use short-circuit evaluation   WARNING  and even has lower precedence than   so you ll usually want to avoid and  An example when and should be used can be found in the Rails Guide under  Avoiding Double Render Errors

User · Answer

and  amp  amp  bind with the precedence that you expect from boolean operators in programming languages   amp  amp  is very strong     is slightly less strong    and and or have lower precedence   For example  unlike      or has lower precedence than      gt  a   false    true    gt  true   gt  a    gt  true   gt  a   false or true    gt  true   gt  a    gt  false   Likewise  unlike  amp  amp   and also has lower precedence than      gt  a   true  amp  amp  false    gt  false   gt  a    gt  false   gt  a   true and false    gt  false   gt  a    gt  true    What s more  unlike  amp  amp  and     and and or bind with equal precedence    gt   puts 1      puts 2   amp  amp   puts 3  1    gt  true  gt   puts 1  or  puts 2  and  puts 3  1 3    gt  true   gt   puts 1  or   puts 2  and  puts 3   1    gt  true   The weakly-binding and and or may be useful for control-flow purposes  see http   devblog avdi org 2010 08 02 using-and-and-or-in-ruby

User · Answer

The Ruby Style Guide says it better than I could      Use  amp  amp     for boolean expressions  and or for control flow   Rule of   thumb  If you have to use outer parentheses  you are using the wrong   operators       boolean expression if some condition  amp  amp  some other condition   do something end    control flow document saved  or document save

User · Answer

The practical difference is binding strength  which can lead to peculiar behavior if you re not prepared for it   foo    foo bar   nil  a   foo and bar     gt  nil a     gt   foo  a   foo  amp  amp  bar     gt  nil a     gt  nil  a    foo and bar      gt  nil a     gt  nil   a   foo   amp  amp  bar     gt  nil a     gt   foo   The same thing works for    and or

[ruby] Difference between "and" and && in Ruby?

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