Simple-Expression-Evaluator
Simple Expression Evaluator
- Quiet · last change 2-15-2022
- ★ 7 on GitHub
README
Simple Expression Evaluator
Simple Expression Evaluator is a simple Math parser supporting the most basic oprerators: +, -, *, /, \ [^1] and Parentheses
Simply pase an expression to the parser, and it will return the result to you, and if anything goes wrong. You'll get an error type (None, Parentheses, Wrong Char, Divide By Zero) and a pointer (PChar) to where in the expression the error where detected.
It's easy to use:
// This project uses Delphi Console https://github.com/JensBorrisholt/DelphiConsole
uses
System.SysUtils,
System.Console in 'System.Console.pas',
SimpleExpressionEvaluator in '..\SimpleExpressionEvaluator.pas';
begin
while True do
begin
Console.ForegroundColor := TConsoleColor.White;
Console.Write('Enter an expression (or an empty string to exit): ');
var Input := Console.ReadLine.Replace(sLineBreak, '');
if Input = '' then
Break;
var eval: TExprEval;
var result := eval.Evaluate(Input);
Console.CursorLeft := 5;
if eval.EvaluationError <> TEvaluationError.None then
begin
Console.ForegroundColor := TConsoleColor.Red;
Console.Write('Error parsing "%s". Error %s at "%s"', [Input, eval.ErrorType, eval.ErrPos]);
end
else
begin
Console.ForegroundColor := TConsoleColor.Green;
Console.Write('"%s" = %s', [Input, FormatFloat('#.##', result)]);
end;
Console.WriteLine;
Console.WriteLine;
end;
end.In this Repo you'll also find a DUintX test project, with 40 tests, testing the parser.
In the test project you'll also see an example of ho to write your own CustomTestCaseAttribute:
type
ExpesionTestAttribute = class(CustomTestCaseAttribute)
protected
FCaseInfo: TestCaseInfo;
function GetCaseInfo: TestCaseInfo; override;
function GetName: string;
function GetValues: TValueArray;
public
constructor Create(const aExpresstion: string; const aExpectedResult: Double; aEvaluationError: TEvaluationError = None; aErrorPos: string = ''); overload;
end;And how to use it:
[TestFixture]
Tests = class
...
public
[Test]
[ExpesionTest('1234', 1234)]
[ExpesionTest('1+2*3', 7)]
procedure SimpleExpressions(const aExpressions: string; const aResult: Double; const aEvaluationError: string; aErrorPos: string);
...[^1]: \ is the oprerator for div. Div is division in which the fractional part (remainder) is discarded.