[refactor] move rbm.stack* + rbm.rnn_helper → stack/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/stack/rnn_helper.py

@@ -0,0 +1,40 @@
+import numpy as np
+
+VOCAB = ' .!?ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
+_CH2IDX = {ch: i for i, ch in enumerate(VOCAB)}
+
+def ch2idx(ch: str) -> int:
+	return _CH2IDX[ch]
+
+def idx2ch(idx: int) -> str:
+	return VOCAB[idx]
+
+
+def concat(v: np.ndarray, c: np.ndarray) -> np.ndarray:
+	return np.concatenate([v, c])
+
+def split(vc: np.ndarray, v_size: np.ndarray|int) -> tuple[np.ndarray, np.ndarray]:
+	n = len(v_size) if isinstance(v_size, np.ndarray) else v_size
+	return vc[:n], vc[n:]
+
+def shift_right(m: np.ndarray) -> np.ndarray:
+	return np.hstack([np.zeros((m.shape[0], 1)), m[:, :-1]])
+
+def shift_left(m: np.ndarray) -> np.ndarray:
+	return np.hstack([m[:, 1:], np.zeros((m.shape[0], 1))])
+
+def shift_up(m: np.ndarray) -> np.ndarray:
+	return np.vstack([m[1:, :], np.zeros((1, m.shape[1]))])
+
+def shift_down(m: np.ndarray) -> np.ndarray:
+	return np.vstack([np.zeros((1, m.shape[1])), m[:-1, :]])
+
+def clamp_one_hot(src_dst: np.ndarray) -> np.ndarray:
+	index = np.argmax(src_dst)
+	result = np.zeros_like(src_dst)
+	result[index] = 1
+	return result
+
+class Rnn:
+	def __init__(self):
+		pass