ca.nengo.math

Interface FunctionInterpreter

All Known Implementing Classes:

DefaultFunctionInterpreter

public interface FunctionInterpreter

The interface Function Interpreters must implement. Responsible for keeping track of and parsing functions.

Method Summary

Methods

Modifier and Type	Method and Description
java.util.Map<java.lang.String,Function>	getRegisteredFunctions() Returns a map of registered functions.
Function	parse(java.lang.String expression, int dimension) Parses a mathematical expression into a Function instance.
void	registerFunction(java.lang.String name, Function function) Registers a non-standard function for use in future interpretation of function expressions.
void	removeRegisteredFunction(java.lang.String name) Removes a registered function.

Method Detail

registerFunction

void registerFunction(java.lang.String name,
                    Function function)

Registers a non-standard function for use in future interpretation of function expressions. Standard function names (eg sin, cos, ln) are not allowed. The Function must be 1-dimensional. Example: suppose you have a sophisticated Function implementation class called FooImpl. You could register is here as registerFunction("foo", new FooImpl()) and thereafter use it in expressions like parse("x1 + x2 * foo(x3)")

Parameters:

name - Short name of function as it is to appear in parsed expressions

function - Function instance

removeRegisteredFunction

void removeRegisteredFunction(java.lang.String name)

Removes a registered function.

Parameters:

name - Name of function to be removed

getRegisteredFunctions

java.util.Map<java.lang.String,Function> getRegisteredFunctions()

Returns a map of registered functions.

Returns:

The registered functions

parse

Function parse(java.lang.String expression,
             int dimension)

Parses a mathematical expression into a Function instance. The function can include the unary operators - and !, the binary operators +-/^*&|, the standard functions sin() cos() tan() asin(), acos(), atan(), exp(), and ln(), and user-defined unary functions functions that have been registered with the registerFunction(...) method. The constant "pi" and literal constants are also allowed. The logical operators produce 1f or 0f, on the basis of whether their operands are > 1/2. Functions must be given in infix notation and can include brackets.

Function operands have the form x0, x1, etc., which serve as placeholders for values that are given at each dimension of the map() method of the resulting function.

An example of a valid expression would be "x0 * (x1 + x2)^x3 * ln(x4/3)"

Parameters:

expression - Mathematical expression

dimension - Input dimension of the desired Function (must be at least as great as any referenced inputs, eg if x3 appears in the expression, the dimension must be at least 4)

Returns:

Instance of a Function implementing the given expression