How to evaluate a math expression given in string form in java


  • Expression Evaluation
  • Math Parser for C# .NET
  • Homework Answers
  • Mathematical Expression Parsers in Java and C++
  • Python – Evaluate Expression given in String
  • Execute and calculate string as a mathematical equation in PHP
  • Expression Evaluation

    Value of x: 0. Now, using Java double based arithmetic in a financial application should be considered harmful, from my point of view. At least if you are not extremely careful with rounding in every step. Therefore the need for BigDecimal support. Fourth feature was the support for Boolean logic, ideally mixable with standard arithmetic.

    And last but not least, of course support for functions and variables, as seen in the examples above. So I sat down and implemented one, that had all what I wanted, plus some more features I caught on the way: Uses BigDecimal for calculation and result Single class implementation, very compact No dependencies to external libraries Precision and rounding mode can be set Supports variables Standard Boolean and mathematical operators Standard basic mathematical and Boolean functions Custom functions and operators can be added at runtime The complete source can be found on GitHub , which is in fact only a single Java file, if you remove all the JUnit test cases and administrative files like license and readme.

    The class com. Expression is all you need to have this handy expression parser and evaluator up and running. Plus a digits exact predefined variable for PI, for free.

    This set of operators, functions and variables can be extended at runtime without modifying the existing class. Adding variables is easy, we have seen that before. Custom operators can be added easily, simply create an instance of Expression. Operator and add it to the expression. Parameters are the operator name, its precedence and if it is left associative. The operators eval method will be called with the BigDecimal values of the operands. All existing operators can also be overridden.

    Create an instance of Expression. Function and add it to the expression. Parameters are the function name and the count of required parameters. The functions eval method will be called with a list of the BigDecimal parameters. All existing functions can also be overridden.

    Math Parser for C# .NET

    Checkout Math Parser for C. NET It is a challenge to evaluate expressions given at runtime with compiled languages. NET programmers are not left out, we have a math parser for you! You can think of bcParser. NET as a safe eval function to evaluate math formulas. NET Platform.

    NET parses and evaluates mathematical expressions given as strings at runtime. NET —. NET Math Parser — simplifies the task for us by implementing the parse and evaluate algorithm. NET saves you valuable time so that you can focus on other aspects of your application and not spend time re-inventing the wheel by re-using bcParser. NET bcParser. NET Math parser is implemented in C. It allows the programmer set the expression as a string, create user defined variables, set their values, create user defined functions and get expression value with one function call.

    The expression can contain arithmetic operators, logical operators, variables, functions, numeric and string literals. Will be discussed later. SetVariable "Y", 3 ; The programmer can implement his own functions in any. NET language and hook them up to the Math Parser object so that they can be used in expressions all with few lines of code.

    The Math Parser reports errors via ParserException. This exception object carries out syntax errors that indicate invalid portion of the mathematical expression. NET allows defining your own functions and variables. If a function definition declares the number of variables it requires, this will be enforced during parse time. A function can also be defined by implementing IFunction interface. GetValueAsDouble ; This design allows you to skip computing some parameters if your program logic allows, or requires it.

    This will translate into speed gains and in some cases this capability helps avoid division by zero errors and other impossible situations. Pow x. GetValueAsDouble , y. That is pretty much all there is to it for user defined functions in bcParser.

    NET Math Parser. Earlier we gave examples of setting variable values before evaluating the expression. When this is not possible, you have the option to register a delegate VariableDelegate that will return values for unknown variables that the parser has encountered. WriteLine parser. Value ; In above code snippet, imagine that K was not known at the time you wrote the program.

    How would that happen? For example some users have database column names as variables and you the programmer do not know the database columns, only the end user knows. But at runtime you are able to compute a value for it and proceed with it.

    To make it happen, you would write a GetVarValue function. NET is generated from the C source code. You can view it online: Math Parser C Documentation. Documentation is also included in the evaluation version and the paid version of the downloads. NET trial download comes as a zip file which contains a trial bcParser. The trial version will expire after a short period, please do not ship the trial version with your products. If the evaluation expires too soon, please let us know and we will send you a new one.

    You can download bcParser. NET evaluation version here. Tackling all of the challenges of implementing a parser is almost impossible within the scope of a broader project where there are pressing requirements in terms of time and functionality to be delivered. Most of us need to focus on the actual business problem at hand and view the mathematical expression parsing aspect of the problem as a side issue.

    Thus, it becomes very very hard to deliver correct, united tested, proven code on time and in budget. Trying to code a expression parser could take an experienced developer a month to write and to test. When such as road block appears, the best way is to find a good component that can easily be integrated into your development project, leaving you free time to focus on other aspects of your project or to simply go home and rest.

    There is peace of mind in using a component that many others have used for many years and flushed out the bugs for you. NET math parser is a well tested, broadly used, simple. NET Class that can save time and money for experienced or novice programmers alike.

    It comes with C source code so you are never stuck with a black box. Purchasing bcParser. The download includes C source code. Upgrades are free for registered users. Licensing is per developer. Site license option is available in the online store page. You can deploy the the component royalty free with your applications as many times as you want. Site license allows any number of developers use the component at your development site. Site licenses can be purchased here.

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    Homework Answers

    Therefore the need for BigDecimal support. Fourth feature was the support for Boolean logic, ideally mixable with standard arithmetic. And last but not least, of course support for functions and variables, as seen in the examples above.

    So I sat down and implemented one, that had all what I wanted, plus some more features I caught on the way: Uses BigDecimal for calculation and result Single class implementation, very compact No dependencies to external libraries Precision and rounding mode can be set Supports variables Standard Boolean and mathematical operators Standard basic mathematical and Boolean functions Custom functions and operators can be added at runtime The complete source can be found on GitHubwhich is in fact only a single Java file, if you remove all the JUnit test cases and administrative files like license and readme.

    The class com. Expression is all you need to have this handy expression parser and evaluator up and running. Plus a digits exact predefined variable for PI, for free. Last Updated : 06 Sep, Evaluate an expression represented by a String.

    The expression can contain parentheses, you can assume parentheses are well-matched. Arithmetic Expressions can be written in one of three forms: Infix Notation: Operators are written between the operands they operate on, e. Prefix Notation: Operators are written before the operands, e.

    Mathematical Expression Parsers in Java and C++

    Infix Expressions are harder for Computers to evaluate because of the additional work needed to decide precedence. NET Platform. NET parses and evaluates mathematical expressions given as strings at runtime.

    NET —. NET Math Parser — simplifies the task for us by implementing the parse and evaluate algorithm. NET saves you valuable time so that you can focus on other aspects of your application and not spend time re-inventing the wheel by re-using bcParser. NET bcParser.

    Python – Evaluate Expression given in String

    NET Math parser is implemented in C. It allows the programmer set the expression as a string, create user defined variables, set their values, create user defined functions and get expression value with one function call.

    The expression can contain arithmetic operators, logical operators, variables, functions, numeric and string literals. Will be discussed later. SetVariable "Y", 3 ; The programmer can implement his own functions in any. NET language and hook them up to the Math Parser object so that they can be used in expressions all with few lines of code.

    The Math Parser reports errors via ParserException. This exception object carries out syntax errors that indicate invalid portion of the mathematical expression. NET allows defining your own functions and variables.

    Execute and calculate string as a mathematical equation in PHP

    If a function definition declares the number of variables it requires, this will be enforced during parse time. A function can also be defined by implementing IFunction interface. GetValueAsDouble ; This design allows you to skip computing some parameters if your program logic allows, or requires it.

    This will translate into speed gains and in some cases this capability helps avoid division by zero errors and other impossible situations. Pow x.


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