#include <stdio.h>
#include <math.h>

void main() {
	double r, area, lon; // long paraula reservada

	printf("Area i longitud circumferencia\n");
	printf("Radi: ");
	scanf("%lf", &r);

	lon = 2 * M_PI * r;
	area = M_PI * pow(r, 2);

	printf("L'area del cercle es %.15lf\n", area);
	printf("El perimetre de la circumferencia es %.15lf\n", lon);
}

/*
https://www.geeksforgeeks.org/difference-float-double-c-cpp/

float is a 32 bit IEEE 754 single precision Floating Point Number1 bit for the
sign, (8 bits for the exponent, and 23* for the value), i.e. float has 7
decimal digits of precision.

double is a 64 bit IEEE 754 double precision Floating Point Number (1 bit for
the sign, 11 bits for the exponent, and 52* bits for the value), i.e. double
has 15 decimal digits of precision.
*/

/*
 * from /usr/include/math.h (or /usr/local/include/math.h):
 *

// Some useful constants.  //
#if defined __USE_MISC || defined __USE_XOPEN
# define M_E		2.7182818284590452354	// e
# define M_LOG2E	1.4426950408889634074	// log_2 e
# define M_LOG10E	0.43429448190325182765	// log_10 e
# define M_LN2		0.69314718055994530942	// log_e 2
# define M_LN10		2.30258509299404568402	// log_e 10
# define M_PI		3.14159265358979323846	// pi
# define M_PI_2		1.57079632679489661923	// pi/2
# define M_PI_4		0.78539816339744830962	// pi/4
# define M_1_PI		0.31830988618379067154	// 1/pi
# define M_2_PI		0.63661977236758134308	// 2/pi
# define M_2_SQRTPI	1.12837916709551257390	// 2/sqrt(pi)
# define M_SQRT2	1.41421356237309504880	// sqrt(2)
# define M_SQRT1_2	0.70710678118654752440	// 1/sqrt(2)
#endif

// The above constants are not adequate for computation using `long double's.
// Therefore we provide as an extension constants with similar names as a
// GNU extension.  Provide enough digits for the 128-bit IEEE quad.
#ifdef __USE_GNU
# define M_El		2.718281828459045235360287471352662498L // e
# define M_LOG2El	1.442695040888963407359924681001892137L // log_2 e
# define M_LOG10El	0.434294481903251827651128918916605082L // log_10 e
# define M_LN2l		0.693147180559945309417232121458176568L // log_e 2
# define M_LN10l	2.302585092994045684017991454684364208L // log_e 10
# define M_PIl		3.141592653589793238462643383279502884L // pi
# define M_PI_2l	1.570796326794896619231321691639751442L // pi/2
# define M_PI_4l	0.785398163397448309615660845819875721L // pi/4
# define M_1_PIl	0.318309886183790671537767526745028724L // 1/pi
# define M_2_PIl	0.636619772367581343075535053490057448L // 2/pi
# define M_2_SQRTPIl	1.128379167095512573896158903121545172L // 2/sqrt(pi)
# define M_SQRT2l	1.414213562373095048801688724209698079L // sqrt(2)
# define M_SQRT1_2l	0.707106781186547524400844362104849039L // 1/sqrt(2)
#endif

*/