added qasm3 adder example

/*

 * quantum ripple-carry adder

 * Cuccaro et al, quant-ph/0410184

 */

OPENQASM 3;

gate ccx a,b,c

{

  h c;

  cx b,c; tdg c;

  cx a,c; t c;

  cx b,c; tdg c;

  cx a,c; t b; t c; h c;

  cx a,b; t a; tdg b;

  cx a,b;

}

gate majority a, b, c {

  cx c, b;

  cx c, a;

  ccx a, b, c;

}

gate unmaj a, b, c {

  ccx a, b, c;

  cx c, a;

  cx a, b;

}

qubit cin;

qubit a[4];

qubit b[4];

qubit cout;

bit ans[5];

// FIXME: left shift casting to handle different type:

// e.g. i4 vs. i64 (shift value)

uint[64] a_in = 1;  

uint[64] b_in = 14; 

for i in [0:4] {

  // FIXME: not able to do this inline....

  bool b1 = bool(a_in[i]);

  bool b2 = bool(b_in[i]);

  if (b1) {

    x a[i];

  }

  if (b2) {

    x b[i];

  }

}

// add a to b, storing result in b

majority cin, b[0], a[0];

for i in [0: 3] { 

  majority a[i], b[i + 1], a[i + 1]; 

}

cx a[3], cout;

for i in [2: -1: -1] { 

  unmaj a[i], b[i+1], a[i+1]; 

}

unmaj cin, b[0], a[0];

measure b[0:3] -> ans[0:3];

measure cout[0] -> ans[4];

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