README.md

Hef.Math.Interpreter

An interpreter that takes a math formula (string) as input, breaks it into a chain of values and operations, and outputs a numeric result. It also handles variable declarations as key/value pairs.

Getting Started

Prerequisites

This software is based on the .Net 2.0 Framework and has no other dependencies.

Installing

There is different options to get it into your own projet.

Github

Clone the repository, or copy/paste the code into your solution.

git clone https://github.com/fsegaud/Hef.Math.Interpreter.git

NuGet Package

You can also install the correpsonding NuGet package at https://www.nuget.org/packages/Hef.Math.Interpreter

Or install it using the NuGet console.

Install-Package Hef.Math.Interpreter -Version 1.1.1

Examples

The interpreter accepts two notation styles. Operations can be written as functions with parenthesis and arguments, or like regular operations with a symbol. There is actually no difference between functions and symbols in the implementation. For instance, the addition can be written add(1, 2) or 1 + 2. Or even add 1 2 or +(1, 2) if you like it.

The complete list of handled operations is availablable at Annex - Handled Operations.

Here is a simple example.

Interpreter interpreter = new Interpreter();
double result = interpreter.Calculate("sqrt(4) + 2"); // -> 4

The following example highlights the use of manually registered local and global variables.

Interpreter interpreter = new Interpreter();
Interpreter.SetGlobalVar("foo", 1d);
interpreter.SetVar("bar", 2d);
double result = interpreter.Calculate("($foo + $bar) * 2"); // -> 6

The following example highlights the use of Hef.Math.IInterpreterContext, that allows the interpreter to access variables provided by other objects.

Interpreter interpreter = new Interpreter();
interpreter.SetContext("player", new Player()));
double result = interpreter.Calculate("$player.level - 1"); // -> 9

class Player : Hef.Math.IInterpreterContext
{
    private int level = 10;

    public bool TryGetVariable(string name, out double value)
    {
        value = 0d;

        if (name == "level")
        {
            value = this.level;
            return true;
        }

        return false;
    }
}

Note About Caching

Each time a formula is calculated, the interpreter has to breaks the formula into nodes and build a tree of operations. This is a time-consumming process.

In order to make it faster, each time a new formula is processed, the intrepreder will keep the generated tree in memory (up to 64). So if the same formula is used again, the tree will be reused, and only the mathematical operations will be recomputed.

If for some reason the cache has to be manually cleared, the Interpreter provides a function to do so.

Interpreter.ForceClearCache();

Contributing

How To Define Additional Operations

The interpreter handles the basic mathmatical operations. If you need more, everything you have to do is open the Interpreter.Operators.cs file, and derive from the corresponding Node class :

• ZeroNode that takes 0 argument.
• UnaryNode that takes 1 argument.
• BinaryNode that takes 2 arguments.

Then add the OperatorAttribute and fill the symbol and priority.

INFO: The OperatorAttribute is stackable.

INFO: Lowest priorities are executed first. Default priority is 2 (functions).

The following example show the implementation of an operator that halves an operand (unary operator). Its symbols will be # and half.

[Operator("#", 2)]
[Operator("half", 2)]
private class HalfNode : UnaryNode
{
    public HalfNode(Node input)
        : base(input)
    {
    }
    
    public override double GetValue(Interpreter interpreter)
    {
        return this.input.GetValue(interpreter) * .5d;
    }
}

The recompile the DLL, and it's done!

Interpreter interpreter = new Interpreter();
double a = interpreter.Calculate("#10"); // -> 5
double b = interpreter.Calculate("half(10)"); // -> 5

DO make a pull request if you want. More operators makes the interpreter better 😄

License

This project is licensed under the MIT License - see the LICENSE.md file for details

Annex - Handled Operations

Category	Function	Symbol	Operation	Comment
BASIC	sign	±	Sign Change	-1 should be written ±1 (atl+0177)
	add	+	Addition
	sub	-	Subtraction
	mult	*	Product
	div	/	Division
	mod	%	Modulo
ADVACED	pow	^	Power
	sqrt		Square Root
	abs		Absolute Value
	round		Round To Integer
	min		Minimum
	max		Maximum
	ceil		Ceil To Upper Integer
	floor		Floor To Lower Integer
	trunc		Truncate Decimal Part
	log		Logarithm
	log10		Logaritme Base 10
	exp	e	Exponential
COMPARISON	eq	==	Equal	Returns 1 if true, 0 otherwise
	ne	!=	Not Equal	Returns 1 if true, 0 otherwise
	gt	>	Greater Than	Returns 1 if true, 0 otherwise
	gte	>=	Greater Or Equal	Returns 1 if true, 0 otherwise
	lt	<	Less Than	Returns 1 if true, 0 otherwise
	lte	<=	Less Or Equal	Returns 1 if true, 0 otherwise
LOGICAL		!	Not	!true => 0, !false => 1
	and	&&	And	true && true => 1, true && false => 0
	or	||	Or	true || false => 1, false || false => 0
TRIGONOMETRY	cos		Cosine
	sin		Sine
	tan		Tangent
	acos		Arccosine
	asin		Arcsine
	atan		Arctangent
	cosh		Hyperbolic Cosine
	sinh		Hyperbolic Sine
	tanh		Hyperbolic Tangent
	deg2rad		Converts degrees to radians
	rad2deg		Converts radians to degrees
RANDOMIZATION	rand		Random	random(a, b) => [a, b]
	dice	d or D	Dice	dice(a, b) or a D b => [a, a * b]
CONSTANTS	pi		Value of PI	3.14159...
	true		True	1
	false		False	0