### F.1 Keywords ¶

The identifiers below are keywords, and may not be used as variable or function names:

#### Categories: ¶

Utility Functions | Variable Declaration | Function Definition | Control Statements | Iterating Structures | Classdef Structures | Execution Environment

#### Alphabetical keyword listing: ¶

__FILE__ | __LINE__ | break | case | catch | classdef | continue | do | else | elseif | end | end_try_catch | end_unwind_protect | endclassdef | endenumeration | endevents | endfor | endfunction | endif | endmethods | endparfor | endproperties | endswitch | endwhile | endenumeration | events | for | function | global | if | methods | otherwise | parfor | persistent | properties | return | switch | try | until | unwind_protect | unwind_protect_cleanup | while

#### Utility Functions: ¶

The function `iskeyword` can be used to quickly check whether an identifier is reserved by Octave.

iskeyword `()` ¶
iskeyword `(name)` ¶

  Return true if name is an Octave keyword.

  If name is omitted, return a list of keywords.

  See also: isvarname, exist.

#### Variable Declaration: ¶

global `var` ¶

  Declare variables to have global scope.

      global x;
      if (isempty (x))
        x = 1;
      endif

  See also: persistent.

persistent `var` ¶

  Declare variables as persistent.

  A variable that has been declared persistent within a function will retain its contents in memory between subsequent calls to the same function. The difference between persistent variables and global variables is that persistent variables are local in scope to a particular function and are not visible elsewhere.

  See also: global.

#### Function Definition: ¶

function `outputs = function_name (input, …)` ¶
function `function_name (input, …)` ¶
function `outputs = function_name` ¶

  Begin a function body with name `function_name`, with outputs as results, and with inputs as parameters.

  The function can later be invoked in Octave using the syntax

      [output1, output2, ...] = function_name (input1, input2, ...)

  See also: return.

endfunction ¶

  Mark the end of a function.

  See also: function.

end ¶

  Last element of an array or the end of any `for`, `parfor`, `if`, `do`, `while`, `function`, `switch`, `try`, or `unwind_protect` block.

  As an index of an array, the magic index `"end"` refers to the last valid entry in an indexing operation.

  Example:

      x = [ 1 2 3; 4 5 6 ];
      x(1,end)
       ⇒ 3
      x(end,1)
       ⇒ 4
      x(end,end)
       ⇒ 6

  Programming notes:

  1. The `end` keyword cannot be used within `subsref`, `subsasgn`, or `substruct` for manual indexing operations.
  2. For custom classes, to enable use of `end` in indexing expressions it must be overloaded with a function definition such as:

         function last_index = end (obj, end_dim, ndim_obj)
           if (end_dim == ndim_obj)
             last_index = prod (size (obj)(end_dim:ndim_obj));
           else
             last_index = size (obj, end_dim);
           endif
         endfunction

     For more information see Object Oriented Programming.

  See also: for, parfor, if, do, while, function, switch, try, unwind_protect.

return ¶

  Return execution control immediately from a function or script to the calling code.

  `return` is used to stop executing code and exit an m-file immediately rather than continuing until the end of the function or script is reached.

  If the function or script was invoked directly, rather than from calling code in an m-file, then Octave returns to the command line.

  See also: function.

#### Control Statements: ¶

if `(cond) … endif` ¶
if `(cond) … else … endif` ¶
if `(cond) … elseif (cond) … endif` ¶
if `(cond) … elseif (cond) … else … endif` ¶

  Begin an if block.

  The conditional cond is true if it is not empty and if all values are nonzero.

      x = 1;
      if (x == 1)
        disp ("one");
      elseif (x == 2)
        disp ("two");
      else
        disp ("not one or two");
      endif

  See also: switch.

else ¶

  Alternate action for an if block.

  See `if` for an example.

  See also: if.

elseif `(cond)` ¶

  Alternate conditional test for an if block.

  The conditional cond is true if it is not empty and if all values are nonzero.

  See `if` for an example.

  See also: if.

endif ¶

  Mark the end of an if block.

  See `if` for an example.

  See also: if.

switch `statement` ¶

  Begin a switch block.

      yesno = "yes";

      switch (yesno)
        case {"Yes" "yes" "YES" "y" "Y"}
          value = 1;
        case {"No" "no" "NO" "n" "N"}
          value = 0;
        otherwise
          error ("invalid value");
      endswitch

  See also: if, case, otherwise.

case `value` ¶
case `{value, …}` ¶

  A case statement in a switch block.

  Octave cases are exclusive and do not fall-through as do C-language cases. A switch statement must have at least one case. See `switch` for an example.

  See also: switch.

otherwise ¶

  The default statement in a switch block which is executed when no other case statements match the input.

  See also: switch, case.

endswitch ¶

  Mark the end of a switch block.

  See `switch` for an example.

  See also: switch.

try ¶

  Begin a try-catch block.

  If an error occurs within a try block, then the catch code will be run and execution will proceed after the catch block (though it is often recommended to use the `lasterr` function to re-throw the error after cleanup is completed).

  See also: catch, unwind_protect.

catch ¶
catch `value` ¶

  Begin the cleanup part of a try-catch block.

  See also: try.

end_try_catch ¶

  Mark the end of a `try-catch` block.

  See also: try, catch.

unwind_protect ¶

  Begin an unwind_protect block.

  If an error occurs within the first part of an unwind_protect block the commands within the unwind_protect_cleanup block are executed before the error is thrown. If an error is not thrown, then the unwind_protect_cleanup block is still executed. In other words, the unwind_protect_cleanup code is guaranteed to execute regardless of success or failure in the unwind_protect block.

  See also: unwind_protect_cleanup, try.

unwind_protect_cleanup ¶

  Begin the cleanup section of an unwind_protect block.

  See also: unwind_protect.

end_unwind_protect ¶

  Mark the end of an unwind_protect block.

  See also: unwind_protect.

#### Iterating Structures: ¶

for `i = range` ¶

  Begin a for loop.

      for i = 1:10
        i
      endfor

  See also: parfor, do, while.

endfor ¶

  Mark the end of a for loop.

  See `for` for an example.

  See also: for.

while `(cond)` ¶

  Begin a while loop.

  The conditional cond is true if it is not empty and if all values are nonzero.

      i = 0;
      while (i < 10)
        i++
      endwhile

  See also: do, endwhile, for, until.

endwhile ¶

  Mark the end of a while loop.

  See `while` for an example.

  See also: do, while.

do ¶

  Begin a do-until loop.

  This differs from a while loop in that the body of the loop is executed at least once.

      i = 0;
      do
        i++
      until (i == 10)

  See also: for, until, while.

until `(cond)` ¶

  End a do-until loop.

  The conditional cond is true if it is not empty and if all values are nonzero.

  See `do` for an example.

  See also: do.

parfor `i = range` ¶
parfor `(i = range, maxproc)` ¶

  Begin a for loop that may execute in parallel.

  A `parfor` loop has the same syntax as a `for` loop. If your Octave session has a parallel processing pool enabled, the iterations of the `parfor` loop will be executed in parallel across the pool’s workers. Otherwise, `parfor` will behave exactly as `for`.

  When operating in parallel mode, a `parfor` loop’s iterations are not guaranteed to occur sequentially, and there are additional restrictions about the data access operations you can do inside the loop body.

  Warning: parallel processing pools are currently unimplemented in Octave; `parfor` currently behaves exactly as a normal `for` loop.

      parfor i = 1:10
        i
      endparfor

  See also: for, do, while.

endparfor ¶

  Mark the end of a parfor loop.

  See `parfor` for an example.

  See also: parfor.

break ¶

  Exit the innermost enclosing do, while, or for loop.

  See also: do, while, for, parfor, continue.

continue ¶

  Jump to the end of the innermost enclosing do, while, or for loop.

  See also: break, do, while, for, parfor.

#### Classdef Structures: ¶

classdef ¶

  Begin a classdef block.

  See also: properties, methods, events, enumeration.

endclassdef ¶

  Mark the end of a classdef definition.

  See also: classdef.

properties ¶

  Mark the beginning of a block of properties in a classdef definition. Note that the function `"properties"` is a function that lists the properties of a classdef class or object.

  See also: endproperties.

endproperties ¶

  Mark the end of a properties block in a classdef definition.

  See also: properties.

methods ¶

  Mark the beginning of a block of methods in a classdef definition. Note that the function `"methods"` is a function that lists the methods of a class or object.

  See also: endmethods.

endmethods ¶

  Mark the end of a methods block in a classdef definition.

  See also: methods.

events ¶

  Begin an events block in a classdef definition.

endevents ¶

  Mark the end of an events block in a classdef definition.

  See also: events.

enumeration ¶

  Begin an enumeration block in a classdef definition.

endenumeration ¶

  Mark the end of an enumeration block in a classdef definition.

  See also: enumeration.

#### Execution Environment: ¶

__FILE__ ¶

  When the lexer recognizes the `"__FILE__"` keyword it returns a character array containing the full name and path of the file that is being executed. `"__FILE__"` will return `"stdin"` if called from the command line.

  See also: __LINE__.

__LINE__ ¶

  When the lexer recognizes the `"__LINE__"` keyword it returns a numeric value containing the current input line number of the function or file being executed. `"__LINE__"` will return `1` if called from the command line.

  See also: __FILE__.