Expressions & Operators

Close                              # a price field
RSI(14)                            # an indicator call
Close - Open                       # arithmetic
Abs(Close - EMA(21))               # a function over arithmetic
(High - Low) / Close * 100         # a compound expression
ATR(14) / ATR(14)[20]              # arithmetic across two bars

# these are the same expression
Close - Open * 2
Close - (Open * 2)

# and these are NOT the same
A AND B OR C            # → (A AND B) OR C
A AND (B OR C)          # → what people usually mean

# the second reading is almost always the intent:
# "trigger fired AND (confirmation A OR confirmation B)"

1// a value comparison reads one bar2const gt = (i: number) => left[i] > right[i];34// a transition reads two, and needs the previous one to exist5const crossesAbove = (i: number) =>6  i > 0 &&7  left[i - 1] <= right[i - 1] &&   // was at or below8  left[i]     >  right[i];          // is now above910// which is why two transitions ANDed almost never fire:11// both must make their crossing on the very same bar12const both = (i: number) => crossesAboveA(i) && crossesAboveB(i);

1function evaluate(group: Group, i: number): boolean {2  if (group.operator === 'AND') {3    for (const child of group.children) {4      // the first false settles it — remaining children are never evaluated5      if (!resolve(child, i)) return false;6    }7    return true;8  }9  for (const child of group.children) {10    if (resolve(child, i)) return true;   // the first true settles it11  }12  return false;13}

# fragile — a doji bar makes the denominator zero
Abs(Close - Open) / (High - Low)  >  0.7

# guarded — the epsilon costs nothing and cannot divide by zero
Abs(Close - Open) / (High - Low + 0.0001)  >  0.7

# also fine, and clearer about intent
AND {
  High - Low  >  0
  Abs(Close - Open) / (High - Low)  >  0.7
}