function calka( a, b, n, func )


Variables = {
	                  f = func,
                    h = ( b-a )/n,
                    w = 0,
                    x1 = a + 0/n  * (b-a)
             }

local _ = Variables

		for i = 1, n do
		    local xi =  ( a + i/n  * (b-a) )
		    local ti = ( ( a + (i-1)/n  * (b-a) ) +_.x1 +1 ) / 2
		    print( xi..": ".._.f(xi) )
		    print( ti..": ".._.f(ti) )
			  _.w = _.w +  _.f( a + i/n  * (b-a) );
		end
		_.w = _.w + ( _.f( a ) + _.f( b )) / 2;
		_.w = _.w * _.h;

    print( "calka: ".._.w );


end
calka( 1, 5, 4, function ( x )
      return x^2 + 2*x;
    end )