// file:    fromBinaryMSBF.rex
// author:  Robert Keller
// purpose: to create a number from a list of bits, most-significant bit first

fromBinaryMSBF(L) = fromBinaryMSBFaux(L, 0);


fromBinaryMSBFaux([], Acc) => Acc;

fromBinaryMSBFaux([A | L], Acc) => 
  fromBinaryMSBFaux(L, 2*Acc + A);

// The accumulator Acc holds the result of the more significant bits already
// converted.  As each new bit is encountered, Acc is doubled, which
// effectively shifts the bits of the result to the left.  The current
// digit A is added in.  This process repeats until all bits are taken
// into account.  The most-significant bit will have been multiplied by 2
// a number of times one less than the length of the list.  The least
// significant bit will be the last to be added.  When the list is decimated,
// the accumulated value is returned.


sys(in, "toBinaryMSBF.rex");	// for test purposes

test() = map(fromBinaryMSBF, map(toBinaryMSBF, range(0, 16)));