This allows you to writeįunctions that behave differently depending on the number of values that Octave also automatically initializes nargout to the number of In addition to setting nargin each time a function is called, The values to be returned may not have compatibleĭimensions, and it is often desirable to give the individual return In this particular case, the two values could have been returned asĮlements of a single array, but that is not always possible orĬonvenient. Here is an example of a function that returns two values, the maximumĮlement of a vector and the index of its first occurrence in the vector. Only one element, this form of the function statement isĮquivalent to the form described in the previous section.
Return values must have at least one element. Names that will hold the values returned from the function. Where name, arg-list, and body have the same meaningĪs before, and ret-list is a comma-separated list of variable Unlike many other computer languages, Octave allows you to defineįunctions that return more than one value. A return statement is assumed at the end of every This statement returns control to the rest of the Octave The body of a user-defined function can contain a return So we check for that possibility too, and issue the error message ifĮither too few or too many arguments have been provided. With more arguments than were expected, doing so is probably an error, For example, we might rewrite theĪlthough Octave does not consider it an error if you call a function Each time a function is called, nargin isĪutomatically initialized to the number of arguments that have actuallyīeen passed to the function. Octave provides each function with an automatic variable called Will probably print an error message that won't really help you trackĭown the source of the error. What if it isĬalled without an argument? Without additional error checking, Octave There is still one additional problem with this function. For example, avg could have beenĮrror ("avg: expecting vector argument") It is a good idea to always make sure that the return variables willĪlways have values, and to produce meaningful error messages when This variable must be definedīefore the end of the function body in order for the function to returnįor example, here is a function that computes the average of theĪnd then called the function with a matrix instead of a vector as theĪrgument, Octave would have printed an error message like this:Įrror: `retval' undefined near line 1 column 10Įrror: evaluating index expression near line 7, column 1īecause the body of the if statement was never executed, and The symbol ret-var is the name of the variable that will hold the Here is the syntax for writing a function that In most cases, you will also want to get some information back from theįunctions you define. In the first argument to the printf statement). `Rise and shine!', followed by a newline character (the `\n' Will cause Octave to ring your terminal's bell and print the message To print a message along with ringing the bell, you might modify theĬalling this function using a statement like this The list of arguments mayīe empty, in which case this form is equivalent to the one shown above. Hold the argument values given in the call. When the function is called, the argument names are used to Where arg-list is a comma-separated list of the function'sĪrguments. The syntax for passing parameters to a function in Octave is Normally, you will want to pass some information to the functions youĭefine. Once this function is defined, you can ask Octave to evaluate it by Stands for the alert character (ASCII 7). The printf statement (see section Input and Output) simply tells
On your terminal (assuming that it is possible to do so): Most important part of the definition, because it says what the functionįor example, here is a function that, when executed, will ring the bell
The function body consists of Octave statements. Share the same pool of names as variables. Letters, digits and underscores, not starting with a digit. In its simplest form, the definition of a function named nameĪ valid function name is like a valid variable name: a sequence of
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