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

fromBinaryLSBF([]) => 0;
fromBinaryLSBF([A | L]) => A + 2*fromBinaryLSBF(L);

// Rationale: The empty list is converted to 0 for completeness
// (there is no point having the function be undefined for []).

// If A is the LSB of the number being created, that number is just
// A + two times the number resulting from the rest of the bits.


// For reference, below is an alternate version using an accumulator:
/*
fromBinaryLSBF(L) = fromBinaryLSBFaux(L, 1, 0);

fromBinaryLSBFaux([], Power, Acc) => Acc;
fromBinaryLSBFaux([A | L], Power, Acc) => 
    fromBinaryLSBFaux(L, 2*Power, A*Power + Acc);
*/

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

test() = map(fromBinaryLSBF, map(toBinaryLSBF, range(0, 16)));