| 1 | #include <fstream.hfa>
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| 2 | #include <stdlib.hfa>
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| 3 | #include <enum.hfa>
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| 4 |
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| 5 | struct MR { double mass, radius; };
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| 6 |
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| 7 | enum( MR ) Planet { // typed enumeration
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| 8 | // mass (kg) radius (km)
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| 9 | MERCURY = { 0.330_E24, 2.4397_E6 },
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| 10 | VENUS = { 4.869_E24, 6.0518_E6 },
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| 11 | EARTH = { 5.976_E24, 6.3781_E6 },
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| 12 | MOON = { 7.346_E22, 1.7380_E6 }, // not a planet
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| 13 | MARS = { 0.642_E24, 3.3972_E6 },
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| 14 | JUPITER = { 1898._E24, 71.492_E6 },
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| 15 | SATURN = { 568.8_E24, 60.268_E6 },
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| 16 | URANUS = { 86.86_E24, 25.559_E6 },
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| 17 | NEPTUNE = { 102.4_E24, 24.746_E6 },
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| 18 | PLUTO = { 1.303_E22, 1.1880_E6 }, // not a planet
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| 19 | };
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| 20 |
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| 21 | enum( double ) { G = 6.6743_E-11 }; // universal gravitational constant (m3 kg-1 s-2)
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| 22 |
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| 23 | static double surfaceGravity( Planet p ) with( p ) {
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| 24 | return G * mass / ( radius \ 2 ); // no qualification, exponentiation
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| 25 | }
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| 26 | static double surfaceWeight( Planet p, double otherMass ) {
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| 27 | return otherMass * surfaceGravity( p );
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| 28 | }
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| 29 |
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| 30 | int main( int argc, char * argv[] ) {
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| 31 | if ( argc != 2 ) exit | "Usage: " | argv[0] | "earth-weight"; // terminate program
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| 32 |
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| 33 | double earthWeight = convert( argv[1] );
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| 34 | double earthMass = earthWeight / surfaceGravity( EARTH );
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| 35 |
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| 36 | Planet rp = fromInt( prng( countof( Planet ) ) ); // select random orbiting body
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| 37 | choose( rp ) { // implicit breaks
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| 38 | case MERCURY, VENUS, EARTH, MARS:
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| 39 | sout | rp | "is a rocky planet";
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| 40 | case JUPITER, SATURN, URANUS, NEPTUNE:
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| 41 | sout | rp | "is a gas-giant planet";
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| 42 | default:
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| 43 | sout | rp | "is not a planet";
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| 44 | }
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| 45 |
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| 46 | for ( p; Planet ) { // enumerate
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| 47 | sout | "Your weight on" | ( p == MOON ? "the" : " " ) | p
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| 48 | | "is" | wd( 1,1, surfaceWeight( p, earthMass ) ) | "kg";
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| 49 | }
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| 50 | }
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