Editing Control flow (section)

=== Case and switch statements ===
{{Main article|Switch statement}}
[[Switch statement]]s (or ''case statements'', or ''multiway branches'') compare a given value with specified constants and take action according to the first constant to match. There is usually a provision for a default action ("else", "otherwise") to be taken if no match succeeds. Switch statements can allow compiler optimizations, such as [[lookup table]]s. In [[dynamic language]]s, the cases may not be limited to constant expressions, and might extend to [[pattern matching]], as in the [[shell script]] example on the right, where the <code>*)</code> implements the default case as a [[glob (programming)|glob]] matching any string. Case logic can also be implemented in functional form, as in [[SQL]]'s <code>decode</code> statement.<!--Perl's implementation of case as a lookup table-->

{| class="wikitable"
|-
! [[Pascal (programming language)|Pascal]]:
! [[Ada (programming language)|Ada]]:
|-
|<syntaxhighlight lang="pascal">
case someChar of
  'a': actionOnA;
  'x': actionOnX;
  'y','z':actionOnYandZ;
  else actionOnNoMatch;
end;
</syntaxhighlight>
|<syntaxhighlight lang="ada">
case someChar is
  when 'a' => actionOnA;
  when 'x' => actionOnX;
  when 'y' | 'z' => actionOnYandZ;
  when others => actionOnNoMatch;
end;
</syntaxhighlight>
|-
! [[C (programming language)|C]]:
! [[Shell script]]:
|-
|<syntaxhighlight lang="c">
switch (someChar) {
  case 'a': actionOnA; break;
  case 'x': actionOnX; break;
  case 'y':
  case 'z': actionOnYandZ; break;
  default: actionOnNoMatch;
}
</syntaxhighlight>
|<syntaxhighlight lang="bash">
case $someChar in 
   a)    actionOnA ;;
   x)    actionOnX ;;
   [yz]) actionOnYandZ ;;
   *)    actionOnNoMatch  ;;
esac
</syntaxhighlight>
|-
! [[Lisp (programming language)|Lisp]]:
! [[Fortran]]:
|-
| <syntaxhighlight lang="lisp">
(case some-char
  ((#\a)     action-on-a)
  ((#\x)     action-on-x)
  ((#\y #\z) action-on-y-and-z)
  (else      action-on-no-match))
</syntaxhighlight>
| <syntaxhighlight lang="fortran">
select case (someChar)
  case ('a')
    actionOnA
  case ('x')
    actionOnX
  case ('y','z')
    actionOnYandZ
  case default
    actionOnNoMatch
end select
</syntaxhighlight>
|}