Exercises How about some programming exercises :)

[Томму 0]

It's simple, someone posts an exercise, the other one solves it, and so on .

Okay, let's start.

Ohm's law Make a class describing a resistor with the following members:

a private data member for the resistance, R

a public member function to set the value of R

a public member function to calculate the current I from the voltage E

a public member function to calculate the voltage E from the current I

a public member function to calculate the power dissipation P from the current I using the formula P = I?E, where E is calculated using the previous member function.

Make a program to test this class.

[nooc9 0]

#include <iostream>class Resistor{   float R;public:   Resistor& setR(float r) { R=r; return *this; }   float getI(float E) { return E/R; }   float getE(float I) { return R*I; }   float getP(float I) { return I*getE(I); }   Resistor() :R(0) {}   Resistor(float r) :R(r) {}};int main() {   Resistor r(5);   std::cout << "Resistor(5).getE(0.5) = " << r.getE(0.5f) << " V" << std::endl;   std::cout << "Resistor(100).getI(12) = " << r.setR(100).getI(12) << " A" << std::endl;   std::cout << "Resistor(1200).getP(0.01) = " << r.setR(1200).getP(0.01) << " W" << std::endl;   return 0;}

Ok, so here is a silly one from me.

Let Variables be a map of string to float:

typedef std::map<std::string,float> Variables;

Let Operation be an abstract class that has the following declaration:

struct Operation {   virtual float evaluate(const Variables& vars) = 0;};

Implement Add, Sub, Mul, Div, Const, Var that extend Operation so that the following example is possible:

// Create expression: (A+10)*(1/(B-3))Mul expression(	Add( Var("A"), Const(10) ),	Div( Const(1),		Sub(Var("B"),Const(3))		)	);// Create variable mapVariables vars;vars["A"] = 2.5;vars["B"] = 7;// Evaluate expression using variables in vars mapfloat result = expression.evaluate(vars);

You may add abstract methods to Operation.
Edited October 28, 2009 by nooc9 (see edit history)