Tutorials

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A simple parser demo

If you want to evaluate a simple math expression like sin(pi/6)+3, first you need to create the Expression that encapsules the string value and then you can use Analyzer to get the result:

#include <iostream>
#include <analitza/analyzer.h>
#include <analitza/value.h>

using namespace std;
using namespace Analitza;

int main(int argc, char *argv[]) {
    QString input("sin(pi/6)+3");
    Expression exp(input); // create a math expression
    Analyzer a; // setup the Analyzer instance with its own Variables module

    a.setExpression(exp); // Analyzer needs to know about expression
    double result = a.calculate().toReal().value(); // get the numeric result

    cout << result << endl;

    return 0;
}

You can also use Expression to make some queries, for example, in regards to the data type of the expression, the next code prints 0 (false):

bool eq = exp.isEquation(); // or a.expression().isEquation()
cout << eq << endl;

Some advanced parsing features

Lets create a variable k = 2.1 and a function f(x) = sin(x) + k. We will calculate values for a lambda expression (our f(x) function) and get the derivative of f(x) (wich is a lambda expression too: d(f(x))=f'(x)):

#include <iostream>
#include <analitza/analyzer.h>
#include <analitza/variables.h>
#include <analitza/value.h>

using namespace std;
using namespace Analitza;

int main(int argc, char *argv[]) {
    Variables *vars = new Variables(); // create a variables container 
    vars->modify("k", 2.1); // add a new variable called k with initial value 2.1

    Expression func("x->sin(x) + k"); // create our lambda f(x)=sin(x) + k

    Cn *x = new Cn(); // create a bound variable to manipulate x in f(x)
    x->setValue(3.14); // set a initial value for x

    Analyzer a(vars); // when calculating, Analyzer will access to variables in vars
    QStack<Object*> runStack; // Analyzer use this stack to calculate f(x)
    runStack.push(x); // add our bound variable to the stack

    Expression result; // an expression instance to save computations and result 

    // play with f(x)
    a.setExpression(func);
    a.setStack(runStack); // this is important to calculate lambda expressions
    result = a.calculateLambda();

    cout << func.toString().toStdString() << endl;
    cout << result.isReal() << endl; // simple query
    cout << result.toReal().value() << endl; // get f(3.14)

    // get the derivative of f(x) and play with it
    Expression dfunc = a.derivative("x");
    a.setExpression(dfunc); // update the expression
    a.setStack(runStack); // this is important, update the stack too
    result = a.calculateLambda();

    cout << dfunc.toString().toStdString() << endl; // get the derivative string
    cout << result.toReal().value() << endl; // derivative of f(x) at x = 3.14

    delete vars; // free the memory

    return 0;
}