Formula is a parser and evaluator for mathematical and logical formula language.
To parse a formula, instantiate the Parser and call the method parser(..).
Expression expression = new Parser().parse("=2*2^2");To evaluate the expression, instantiate an Evaluator and call evaluate(..).
Evaluator evaluator = new Evaluator();
int result = evaluator.evaluate(expression);Here is a bit more complicated example with user defined variables, functions und other formulas wich are used inside target one.
// Define variables
Map<String, Object> variables = new HashMap<>();
variables.put("a", 1);
variables.put("text1", "TEXT_1");
variables.put("text2", "TEXT_2");
// Define functions
Map<String, IFunction> functions = new HashMap<>();
functions.put("sqrt", value -> Math.sqrt((Double)value[0]));
// Define formulas
Map<String, Expression> formulas = new HashMap<>();
formulas.put("f1", new Parser().parse("=a*2"));
formulas.put("f2", new Parser().parse("=a*3"));
// Use it all
Evaluator evaluator = new Evaluator(functions, variables, formulas);
Expression expression = new Parser().parse("=5 * when(text1=text2;=f1;=f2)");
evaluator.evaluate(expression);
// The result is 15.0
double result = evaluator.evaluate(expression);The formula language supports a number of built-in mathematical and comparison operators and user defined variables, functions and references to other formulas.
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A formula should be started with
=character. Although it is optional. -
Mathematical operators:
+,-,*,/,^ -
Comparison operators:
<,<=,=,>=,>and<> -
A variable is a string which consist letter and number characters and must begin with a letter.
-
A function is a string (name of the function) with subsequent
(and)characters. The function may have parametrs. They must be placed between(and). The multiple parameters must be delimited by the;character. -
A formula reference begins with
=character folowing by a string (name of the formula).
Apache License Version 2.0 (see https://raw.githubusercontent.com/eduardsdv/formula/master/LICENSE file for the full text)