PDA for Addition

Push-down automaton for unary addition

push E
push TX -> TX
push FY -> FYX  Reject

function delta(c, p) { // Unary addition
    if (p=='E') return "TX";
    if (c=='+' && p=='X') return "+TX";
    if (c=='-' && p=='X') return "-TX";
	if ( p=='X') return "";
    if (p=='T') return "FY";
	
	if (c=='*' && p=='Y') return "*FY";
	if (c=='/' && p=='Y') return "/FY";
	if ( p=='Y') return "";
	if (c=='(' && p=='F') return "(E)";
	if (c=='n' && p=='F') return "n";
	if (c=='i' && p=='F') return "i(E)";
    return null;  //default -- no transition
	
}
function accept(w, init='E') {
    //w: input String
    //init: start symbol
    //S: stack as Array
    let txt = "push "+init
    let i = 0, m = w.length, S = [init]
    while (i < m && S.length > 0) {
        let c = w[i], p = S.pop()
        if (c == p) { //input matches stack  
            i++; txt += "\nmatch "+c
        } else { //find a valid transition
            let d = delta(c, p)
            if (d == null) break;
            let A = d.split('').reverse()
            for (let x of A) S.push(x)
            txt += "\npush "+d
        }
        txt += " -> "
        for (let j=S.length-1; j>=0; j--) 
            txt += S[j]
    }
    input.selectionStart = i
    input.selectionEnd = i+1
    let a = (i == m && S.length == 0)
    return txt+'  '+(a? "Accept" : "Reject")
}