Is there a do while loop in Ruby

Question

I m using this code to let the user enter in names while the program stores them in an array until they enter an empty string  they must press enter after each name    people      info    a    must fill variable with something  otherwise loop won t execute  while not info empty      info   gets chomp     people     Person new info   if not info empty  end   This code would look much nicer in a do     while loop   people       do     info   gets chomp     people     Person new info   if not info empty  while not info empty    In this code I don t have to assign info to some random string   Unfortunately this type of loop doesn t seem to exist in Ruby  Can anybody suggest a better way of doing this

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Like this   people       begin   info   gets chomp   people     Person new info   if not info empty  end while not info empty    Reference  Ruby s Hidden do    while    Loop

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From what I gather  Matz does not like the construct  begin      lt multiple lines of code gt  end while  lt cond gt    because  it s semantics is different than   lt single line of code gt  while  lt cond gt    in that the first construct executes the code first before checking the condition  and the second construct tests the condition first before it executes the code  if ever   I take it Matz prefers to keep the second construct because it matches one line construct of if statements   I never liked the second construct even for if statements  In all other cases  the computer executes code left-to-right  eg     and  amp  amp   top-to-bottom  Humans read code left-to-right top-to-bottom   I suggest the following constructs instead   if  lt cond gt  then  lt one line code gt         matches case-when-then statement  while  lt cond gt  then  lt one line code gt    lt one line code gt  while  lt cond gt   begin  lt multiple line code gt  end while  lt cond gt    or something similar but left-to-right   I don t know if those suggestions will parse with the rest of the language  But in any case I prefere keeping left-to-right execution as well as language consistency

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CAUTION   The begin  lt code gt  end while  lt condition gt  is rejected by Ruby s author Matz  Instead he suggests using Kernel loop  e g   loop do      some code here   break if  lt condition gt  end    Here s an email exchange in 23 Nov 2005 where Matz states     gt  Don t use it please   I m regretting this feature  and I d like to   gt  remove it in the future if it s possible     I m surprised   What do you regret about it   Because it s hard for users to tell    begin  lt code gt  end while  lt cond gt   works differently from     lt code gt  while  lt cond gt    RosettaCode wiki has a similar story      During November 2005  Yukihiro Matsumoto  the creator of Ruby  regretted this loop feature and suggested using Kernel loop

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ppl      while  input gets chomp   if  input empty    ppl  lt  lt  input  else  p ppl  puts  Goodbye   break  end end

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I found the following snippet while reading the source for Tempfile initialize in the Ruby core library  begin   tmpname   File join tmpdir  make tmpname basename  n     lock   tmpname     lock    n    1 end while   cleanlist include  tmpname  or   File exist  lock  or File exist  tmpname   At first glance  I assumed the while modifier would be evaluated before the contents of begin   end  but that is not the case  Observe   gt  gt  begin   gt    puts  quot do    while    quot    gt  gt  end while false do    while      gt  nil  As you would expect  the loop will continue to execute while the modifier is true   gt  gt  n   3   gt  3  gt  gt  begin   gt    puts n  gt  gt    n -  1  gt  gt  end while n  gt  0 3 2 1   gt  nil  While I would be happy to never see this idiom again  begin   end is quite powerful  The following is a common idiom to memoize a one-liner method with no params  def expensive    expensive     2   2 end  Here is an ugly  but quick way to memoize something more complex  def expensive    expensive         begin       n   99       buf    quot  quot         begin         buf  lt  lt   quot   n  bottles of beer on the wall n quot                         n -  1       end while n  gt  0       buf  lt  lt   quot no more bottles of beer quot       end end   Originally written by Jeremy Voorhis   The content has been copied here because it seems to have been taken down from the originating site   Copies can also be found in the Web Archive and at Ruby Buzz Forum   -Bill the Lizard

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How about this   people       until  info   gets chomp  empty    people     Person new info   end

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This works correctly now   begin       statment end until  lt condition gt    But  it may be remove in the future  because the begin statement is counterintuitive  See  http   blade nagaokaut ac jp cgi-bin scat rb ruby ruby-core 6745  Matz  Ruby   s Creator  recommended doing it this way   loop do               break if  lt condition gt  end

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Here s the full text article from hubbardr s dead link to my blog   I found the following snippet while reading the source for Tempfile initialize in the Ruby core library   begin   tmpname   File join tmpdir  make tmpname basename  n     lock   tmpname     lock    n    1 end while   cleanlist include  tmpname  or   File exist  lock  or File exist  tmpname    At first glance  I assumed the while modifier would be evaluated before the contents of begin   end  but that is not the case  Observe    gt  gt  begin   gt    puts  do    while       gt  gt  end while false do    while      gt  nil   As you would expect  the loop will continue to execute while the modifier is true    gt  gt  n   3   gt  3  gt  gt  begin   gt    puts n  gt  gt    n -  1  gt  gt  end while n  gt  0 3 2 1   gt  nil   While I would be happy to never see this idiom again  begin   end is quite powerful  The following is a common idiom to memoize a one-liner method with no params   def expensive    expensive     2   2 end   Here is an ugly  but quick way to memoize something more complex   def expensive    expensive         begin       n   99       buf             begin         buf  lt  lt     n  bottles of beer on the wall n                         n -  1       end while n  gt  0       buf  lt  lt   no more bottles of beer       end end

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Here s another one   people      1 times do   info   gets chomp   unless info empty       people     Person new info       redo   end end

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a   1 while true   puts a   a    1   break if a  gt  10 end

[ruby] Is there a "do ... while" loop in Ruby?

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