73 lines
1.9 KiB
JavaScript
73 lines
1.9 KiB
JavaScript
// basic building blocks allowed by the rules are ~, &, and |, we'll fake these
|
|
// in a way that makes what they do (at least when you use them) more obvious
|
|
// than the other available options do.
|
|
|
|
function not(a) {
|
|
if (arePseudoBin(a))
|
|
return a == 1 ? 0 : 1;
|
|
}
|
|
|
|
function and(a, b) {
|
|
if (arePseudoBin(a, b))
|
|
return a + b < 2 ? 0 : 1;
|
|
}
|
|
|
|
function nand(a, b) {
|
|
if (arePseudoBin(a, b))
|
|
return not(and(a, b));
|
|
}
|
|
|
|
function or(a, b) {
|
|
if (arePseudoBin(a, b))
|
|
return nand(nand(a,a), nand(b,b));
|
|
}
|
|
|
|
function xor(a, b) {
|
|
if (arePseudoBin(a, b))
|
|
return nand(nand(nand(a,b), a), nand(nand(a,b), b));
|
|
}
|
|
|
|
function halfAdder(a, b) {
|
|
if (arePseudoBin(a, b))
|
|
return { carry: and(a, b), sum: xor(a, b) };
|
|
}
|
|
|
|
function fullAdder(a, b, c) {
|
|
if (arePseudoBin(a, b, c)) {
|
|
var h0 = halfAdder(a, b),
|
|
h1 = halfAdder(h0.sum, c);
|
|
return {carry: or(h0.carry, h1.carry), sum: h1.sum };
|
|
}
|
|
}
|
|
|
|
function fourBitAdder(a, b) {
|
|
if (typeof a.length == 'undefined' || typeof b.length == 'undefined')
|
|
throw new Error('bad values');
|
|
// not sure if the rules allow this, but we need to pad the values
|
|
// if they're too short and trim them if they're too long
|
|
var inA = Array(4),
|
|
inB = Array(4),
|
|
out = Array(4),
|
|
i = 4,
|
|
pass;
|
|
|
|
while (i--) {
|
|
inA[i] = a[i] != 1 ? 0 : 1;
|
|
inB[i] = b[i] != 1 ? 0 : 1;
|
|
}
|
|
|
|
// now we can start adding... I'd prefer to do this in a loop,
|
|
// but that wouldn't be "connecting the other 'constructive blocks',
|
|
// in turn made of 'simpler' and 'smaller' ones"
|
|
|
|
pass = halfAdder(inA[3], inB[3]);
|
|
out[3] = pass.sum;
|
|
pass = fullAdder(inA[2], inB[2], pass.carry);
|
|
out[2] = pass.sum;
|
|
pass = fullAdder(inA[1], inB[1], pass.carry);
|
|
out[1] = pass.sum;
|
|
pass = fullAdder(inA[0], inB[0], pass.carry);
|
|
out[0] = pass.sum;
|
|
return out.join('');
|
|
}
|