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octave: Calling Functions

 
 8.2 Calling Functions
 =====================
 
 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.  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, and is allowed to be a list of variable names or index
DONTPRINTYET  expressions.  See also Index Expressions, and *noteAssignment
DONTPRINTYET  expressions.  See also Index Expressions, and Assignment

 Ops.
 

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