(octave.info)Calling Functions

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8.2 Calling Functions
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A “function” is a name for a particular calculation.  Because it has a
name, you can ask for it by name at any point in the program.  For
example, the function ‘sqrt’ computes the square root of a number.

   A fixed set of functions are “built-in”, which means they are
available in every Octave program.  The ‘sqrt’ function is one of these.
In addition, you can define your own functions.  Note: Functions and
Scripts, for information about how to do this.

   The way to use a function is with a “function call” expression, which
consists of the function name followed by a list of “arguments” in
parentheses.  The arguments are expressions which give the raw materials
for the calculation that the function will do.  When there is more than
one argument, they are separated by commas.  If there are no arguments,
you can omit the parentheses, but it is a good idea to include them
anyway, to clearly indicate that a function call was intended.  Here are
some examples:

     sqrt (x^2 + y^2)      # One argument
     ones (n, m)           # Two arguments
     rand ()               # No arguments

   Each function expects a particular number of arguments.  For example,
the ‘sqrt’ function must be called with a single argument, the number to
take the square root of:

     sqrt (ARGUMENT)

   Some of the built-in functions take a variable number of arguments,
depending on the particular usage, and their behavior is different
depending on the number of arguments supplied.

   Like every other expression, the function call has a value, which is
computed by the function based on the arguments you give it.  In this
example, the value of ‘sqrt (ARGUMENT)’ is the square root of the
argument.  A function can also have side effects, such as assigning the
values of certain variables or doing input or output operations.

   Unlike most languages, functions in Octave may return multiple
values.  For example, the following statement

     [u, s, v] = svd (a)

computes the singular value decomposition of the matrix ‘a’ and assigns
the three result matrices to ‘u’, ‘s’, and ‘v’.

   The left side of a multiple assignment expression is itself a list of
expressions, that is, a list of variable names potentially qualified by
index expressions.  See also Note: Index Expressions, and Note:
Assignment Ops.

Call by Value

Recursion

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