11.11.3 Inline Functions

An inline function is created from a string containing the function body using the inline function. The following code defines the function f(x) = x^2 + 2.

f = inline ("x^2 + 2");

After this it is possible to evaluate f at any x by writing f(x).

Caution: MATLAB has begun the process of deprecating inline functions. At some point in the future support will be dropped and eventually Octave will follow MATLAB and also remove inline functions. Use anonymous functions in all new code.

: inline (str)

: inline (str, arg1, …)

: inline (str, n)

Create an inline function from the character string str.

If called with a single argument, the arguments of the generated function are extracted from the function itself. The generated function arguments will then be in alphabetical order. It should be noted that i and j are ignored as arguments due to the ambiguity between their use as a variable or their use as an built-in constant. All arguments followed by a parenthesis are considered to be functions. If no arguments are found, a function taking a single argument named x will be created.

If the second and subsequent arguments are character strings, they are the names of the arguments of the function.

If the second argument is an integer n, the arguments are "x", "P1", …, "PN".

Programming Note: The use of inline is discouraged and it may be removed from a future version of Octave. The preferred way to create functions from strings is through the use of anonymous functions (see Anonymous Functions) or str2func.

See also: argnames, formula, vectorize, str2func.

: argnames (fun)

Return a cell array of character strings containing the names of the arguments of the inline function fun.

See also: inline, formula, vectorize.

: formula (fun)

Return a character string representing the inline function fun.

Note that char (fun) is equivalent to formula (fun).

See also: char, argnames, inline, vectorize.

: vars = symvar (str)

Identify the symbolic variable names in the string str.

Common constant names such as i, j, pi, Inf and Octave functions such as sin or plot are ignored.

Any names identified are returned in a cell array of strings. The array is empty if no variables were found.

Example:

symvar ("x^2 + y^2 == 4")
⇒ {
     [1,1] = x
     [2,1] = y
   }