Difference between or and in Ruby

Question

What s the difference between the or and    operators in Ruby  Or is it just preference

User · Answer

or is NOT the same as     Use only    operator instead of the or operator   Here are some reasons  The    or operator has a lower precedence than     or has a lower precedence than the   assignment operator  and and or have the same precedence  while  amp  amp  has a higher precedence than

User · Answer

and or are for control flow    Ruby will not allow this as valid syntax   false    raise  Error    However this is valid   false or raise  Error    You can make the first work  with    but using or is the correct method   false     raise  Error

User · Answer

It s a matter of operator precedence      has a higher precedence than or   So  in between the two you have other operators including ternary       and assignment     so which one you choose can affect the outcome of statements   Here s a ruby operator precedence table   See this question for another example using and  amp  amp    Also  be aware of some nasty things that could happen    a   false    true     gt  true a     gt  true  a   false or true     gt  true a     gt  false   Both of the previous two statements evaluate to true  but the second sets a to false since   precedence is lower than    but higher than or

User · Answer

As the others have already explained  the only difference is the precedence  However  I would like to point out that there are actually two differences between the two    and  or and not have much lower precedence than  amp  amp      and   and and or have the same precedence  while  amp  amp  has higher precedence than      In general  it is good style to avoid the use of and  or and not and use  amp  amp      and   instead   The Rails core developers  for example  reject patches which use the keyword forms instead of the operator forms    The reason why they exist at all  is not for boolean formulae but for control flow  They made their way into Ruby via Perl s well-known do this or do that idiom  where do this returns false or nil if there is an error and only then is do that executed instead   Analogous  there is also the do this and then do that idiom    Examples   download file via fast connection or download via slow connection download latest currency rates and store them in the cache   Sometimes  this can make control flow a little bit more fluent than using if or unless   It s easy to see why in this case the operators have the  wrong   i e  identical  precedence  they never show up together in the same expression anyway  And when they do show up together  you generally want them to be evaluated simply left-to-right

User · Answer

The way I use these operators         amp  amp  are for boolean logic  or  and are for control flow  E g   do smth if may be    may be -- we evaluate the condition here  do smth or do smth else -- we define the workflow  which is equivalent to do smth else unless do smth  to give a simple example    gt  puts  a   amp  amp   b  b   gt  puts  a  and  b  a   A well-known idiom in Rails is render and return  It s a shortcut for saying return if render  while render  amp  amp  return won t work  See   Avoiding Double Render Errors  in the Rails documentation for more information

User · Answer

puts false or true --  prints  false  puts false    true --  prints  true

User · Answer

Both or and    evaluate to true if either operand is true  They evaluate their second operand only if the first is false    As with and  the only difference between or and    is their precedence   Just to make life interesting  and and or have the same precedence  while  amp  amp  has a higher precedence than

User · Answer

Just to add to mopoke s answer  it s also a matter of semantics  or is considered to be a good practice because it reads much better than

[ruby] Difference between "or" and || in Ruby?

Examples related to ruby

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