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__.