// quantum computing emulation library
//
// R. Perry, Jan. 2018
//

// macros:
//
//   DRAND	0.0 <= d < 1.0
//   IRAND	0 <= i < n
//
#define DRAND    (rand()/(RAND_MAX+1.0))
#define IRAND(n) ((unsigned long)(DRAND*(n)))
//
// print options:
//
#define PRINT_TANGLE -1 // entanglement measure
#define PRINT_LABELS  1 // decimal state labels
#define PRINT_BITS    2 // binary state indices and probabilities

// typedefs:
//
//   State	qubit register
//   Func	function type for operate()
//
typedef struct State
{
  unsigned int n;     // number of bits
  unsigned long N;    // number of states, N = 2**n
  double _Complex *a; // N amplitudes
}
State;
//
typedef unsigned long (*Func) (unsigned long, unsigned long, unsigned long); 

// functions:
//
//   SRAND	set srand() using time(0) or SRAND environment variable
//
//   Q		allocate a new state vector, uninitialized
//   zero	set state vector to all zeros
//   init	initialize state vector
//   swap	swap two states
//   product	tensor product
//   tangle	trace distance as a measure of entanglement
//   H		Hadamard transformation on one qubit
//   Hra	Hadamard with non-resonant pulse error
//   Hrp	Hadamard with phase shift error
//   X		NOT transformation on one qubit
//   Z		phase-flip on one qubit
//   CX		controlled NOT on one qubit
//   M		measurement, uses DRAND
//   reduce	reduce state based on a measurement
//   collapse   collapse state based on a measurement of one qubit
//   operate	q = (a,b) -> (a,f(a,b,z))
//   qfft	quantum FFT
//   fft	classical FFT
//
//   printb	print in binary
//   print	display message and qubit state or entanglement measure
//   error	print error message and exit
//
//   abs2	complex magnitude squared
//   emalloc	malloc with exit on error
//
unsigned int SRAND( void);
State Q( int n);
void zero( State q);
void init( State q, unsigned long k, int rphase);
void swap( State q, unsigned long i, unsigned long j);
State product( State r, State s);
double tangle( State q, unsigned int k);
void H( State q, unsigned int k);
void Hra( State q, unsigned int k, double ra);
void Hrp( State q, unsigned int k, double rp);
void X( State q, unsigned int k);
void Z( State q, unsigned int k);
void CX( State q, unsigned int c, unsigned int k);
unsigned long M( State q);
State reduce( State q, unsigned int n, unsigned long m);
void collapse( State q, unsigned int k, unsigned int m);
void operate( State q, unsigned int n, Func f, unsigned long z);
void qfft( State q, int inv);
void fft( double _Complex *X, unsigned long N, int inv);
//
void printb( unsigned long x, unsigned int n);
void print( const char *msg, State q, int option);
void error( const char *msg);
//
double abs2( double _Complex x);
void *emalloc( unsigned long size);