add

ccxt/static_dependencies/lark/parsers/earley_common.py

@@ -0,0 +1,42 @@
+"""This module implements useful building blocks for the Earley parser
+"""
+
+
+class Item:
+    "An Earley Item, the atom of the algorithm."
+
+    __slots__ = ('s', 'rule', 'ptr', 'start', 'is_complete', 'expect', 'previous', 'node', '_hash')
+    def __init__(self, rule, ptr, start):
+        self.is_complete = len(rule.expansion) == ptr
+        self.rule = rule    # rule
+        self.ptr = ptr      # ptr
+        self.start = start  # j
+        self.node = None    # w
+        if self.is_complete:
+            self.s = rule.origin
+            self.expect = None
+            self.previous = rule.expansion[ptr - 1] if ptr > 0 and len(rule.expansion) else None
+        else:
+            self.s = (rule, ptr)
+            self.expect = rule.expansion[ptr]
+            self.previous = rule.expansion[ptr - 1] if ptr > 0 and len(rule.expansion) else None
+        self._hash = hash((self.s, self.start, self.rule))
+
+    def advance(self):
+        return Item(self.rule, self.ptr + 1, self.start)
+
+    def __eq__(self, other):
+        return self is other or (self.s == other.s and self.start == other.start and self.rule == other.rule)
+
+    def __hash__(self):
+        return self._hash
+
+    def __repr__(self):
+        before = ( expansion.name for expansion in self.rule.expansion[:self.ptr] )
+        after = ( expansion.name for expansion in self.rule.expansion[self.ptr:] )
+        symbol = "{} ::= {}* {}".format(self.rule.origin.name, ' '.join(before), ' '.join(after))
+        return '%s (%d)' % (symbol, self.start)
+
+
+# class TransitiveItem(Item):
+#   ...   # removed at commit 4c1cfb2faf24e8f8bff7112627a00b94d261b420