Create new parser (works for lists so far)

grammar

@@ -0,0 +1,42 @@
+integer := ...
+string := ...
+note := ...
+identifier := ...
+
+expr := integer
+expr := string
+expr := note
+expr := identifier
+expr := access
+expr := assignment
+expr := functionCall
+
+# left associative
+access := expr '.' expr
+
+# right associative
+asterisk := expr '*' stmt
+
+stmt := asterisk
+stmt := block
+stmt := return
+stmt := functionDefinition
+
+# right associative
+assignment := identifier '=' expr
+
+list := '(' ')'
+list := '(' expr listTail
+
+listTail := expr ', ' listTail
+listTail := ')'
+
+percent := integer '%'
+
+return := 'return' expr
+
+block := '{' stmt* '}'
+
+functionCall := identifier list
+
+functionDefinition := 'function' identifier list block

reduced-grammar

@@ -0,0 +1,42 @@
+# Tokenizer
+DIGIT = [0-9]
+ID = [a-zA-Z_]
+CHAR = ... \ '"'
+PITCH = 'c' | 'd' | 'e' | 'f' | 'g' | 'a' | 'h'
+PITCH_MODIFIER = 'b' | '#'
+
+integer := '-' DIGIT+ | DIGIT+
+string := '"' CHAR* '"'
+note := '@' PITCH PITCH_MODIFIER? DIGIT? ['.' DIGIT+ 'd'?]?
+identifier := ID [ID|DIGIT]*
+percent := DIGIT+ '%'
+
+# Parser
+expr := integer accessTail | integer
+expr := percent accessTail | percent
+expr := string accessTail | string
+expr := note accessTail | note
+expr := identifier accessTail | identifier '=' expr | functionCall | identifier
+expr := list accessTail | list
+expr := functionCall accessTail | functionCall
+
+functionCall := identifier list
+
+accessTail := '.' expr accessTail | e
+
+list := '[' ']' | '[' expr listTail
+listTail := expr ', ' listTail | ']'
+
+argList := '(' ')' | '(' expr argListTail
+argListTail := expr ', ' argListTail | ')'
+
+block := '{' stmt* '}'
+
+stmt := expr asteriskTail | expr #nie wiem czy zamiast 'expr asteriskTail' nie powinno być wprost co może wyprodukować iterator dla asterisk
+asteriskTail := '*' stmt | e
+stmt := block
+stmt := 'return' expr
+stmt := 'function' identifier list block
+
+program := stmt*
+

smnp/ast/parsers/access.py

@@ -8,7 +8,7 @@ from smnp.token.type import TokenType
 # i potem sprawdzać przy wszystkich parent.pop(-1) czy pobrany z parenta element
 # jest rzeczywiście wyrażeniem, bo teraz możliwe jest np. {}.fun()
 def parseAccess(input, parent):
-    if input.current().type == TokenType.DOT:
+    if input.isCurrent(TokenType.DOT):
         token = input.current()
         input.ahead()
 

smnp/ast/parsers/assignment.py

@@ -1,2 +0,0 @@
-
-

smnp/ast/parsers/asterisk.py

@@ -5,7 +5,7 @@ from smnp.token.type import TokenType
 
 # asterisk -> expr '*' stmt
 def parseAsterisk(expr, input, parent):
-    if input.hasMore() and input.current().type == TokenType.ASTERISK:
+    if input.hasMore() and input.isCurrent(TokenType.ASTERISK):
         token = input.current()
         input.ahead()
 

smnp/ast/parsers/block.py

@@ -12,7 +12,7 @@ def parseBlock(input, parent):
         node = BlockNode(parent, token.pos)
 
         # '}'
-        if input.hasCurrent() and input.current().type == TokenType.CLOSE_BRACKET:
+        if input.isCurrent(TokenType.CLOSE_BRACKET):
             input.ahead()
             return node
 
@@ -28,7 +28,7 @@ def parseBlock(input, parent):
 # blockItem -> stmt | '}'
 def parseBlockItem(input, parent):
     # '}'
-    if input.hasCurrent() and input.current().type == TokenType.CLOSE_BRACKET:
+    if input.isCurrent(TokenType.CLOSE_BRACKET):
         close = CloseBlockNode(parent, input.current().pos)
         input.ahead()
         return close

smnp/ast/parsers/colon.py

@@ -6,7 +6,7 @@ from smnp.token.type import TokenType
 
 # colon -> expr ':' expr
 def parseColon(expr1, input, parent):
-    if input.hasCurrent() and input.current().type == TokenType.COLON:
+    if input.isCurrent(TokenType.COLON):
         token = input.current()
         input.ahead()
         expr2 = parseExpression(input, parent)

smnp/ast/parsers/function.py

@@ -7,7 +7,7 @@ from smnp.token.type import TokenType
 
 
 def parseFunctionDefinition(input, parent):
-    if input.current().type == TokenType.FUNCTION:
+    if input.isCurrent(TokenType.FUNCTION):
         token = input.current()
         input.ahead()
 

smnp/ast/parsers/identifier.py

@@ -3,12 +3,13 @@ from smnp.ast.node.function import FunctionCallNode
 from smnp.ast.node.identifier import IdentifierNode
 from smnp.ast.parsers.expression import parseExpression
 from smnp.ast.parsers.list import parseList
+from smnp.ast.tools import greedy
 from smnp.token.type import TokenType
 
 
 # id -> IDENTIFIER
 def parseIdentifier(input, parent):
-    if input.current().type == TokenType.IDENTIFIER:
+    if input.isCurrent(TokenType.IDENTIFIER):
         identifier = IdentifierNode(input.current().value, parent, input.current().pos)
         input.ahead()
 
@@ -28,7 +29,7 @@ def parseIdentifierOrFunctionCallOrAssignment(input, parent):
             token = input.current()
             input.ahead()
 
-            expr = parseExpression(input, parent)
+            expr = greedy(parseExpression)(input, parent)
 
             assignment = AssignmentNode(identifier, expr, parent, token.pos)
             identifier.parent = assignment

smnp/ast/parsers/integer.py

@@ -5,7 +5,7 @@ from smnp.token.type import TokenType
 
 # int -> INTEGER
 def parseInteger(input, parent):
-    if input.current().type == TokenType.INTEGER:
+    if input.isCurrent(TokenType.INTEGER):
         integer = IntegerLiteralNode(int(input.current().value), parent, input.current().pos)
         input.ahead()
 
@@ -17,7 +17,7 @@ def parseInteger(input, parent):
 # int -> int
 def parseIntegerAndPercent(input, parent):
     integer = parseInteger(input, parent)
-    if integer is not None and input.hasCurrent() and input.current().type == TokenType.PERCENT:
+    if integer is not None and input.isCurrent(TokenType.PERCENT):
         percent = PercentNode(integer, parent, input.current().pos)
         integer.parent = percent
         input.ahead()

smnp/ast/parsers/list.py

@@ -1,17 +1,17 @@
 from smnp.ast.node.list import ListNode, ListItemNode, CloseListNode
 from smnp.ast.parsers.expression import parseExpression
-from smnp.ast.tools import rollup, assertToken
+from smnp.ast.tools import greedy, assertToken
 from smnp.token.type import TokenType
 
 
 # list -> CLOSE_PAREN | expr listTail
 def parseList(input, parent):
-    if input.current().type == TokenType.OPEN_PAREN:
+    if input.isCurrent(TokenType.OPEN_PAREN):
         node = ListNode(parent, input.current().pos)
         input.ahead()
 
         # list -> CLOSE_PAREN (end of list)
-        if input.hasCurrent() and input.current().type == TokenType.CLOSE_PAREN:
+        if input.isCurrent(TokenType.CLOSE_PAREN):
             close = CloseListNode(node, input.current().pos)
             node.append(close)
             input.ahead()
@@ -20,7 +20,7 @@ def parseList(input, parent):
             # list -> expr listTail
         if input.hasCurrent():
             token = input.current()
-            expr = parseExpression(input, node)
+            expr = greedy(parseExpression)(input, parent)
             item = ListItemNode(expr, node, token.pos)
             expr.parent = item
             node.append(item)
@@ -33,7 +33,7 @@ def parseList(input, parent):
 # listTail -> COMMA expr listTail | CLOSE_PAREN
 def parseListTail(input, parent):
     # listTail -> CLOSE_PAREN
-    if input.hasCurrent() and input.current().type == TokenType.CLOSE_PAREN:
+    if input.isCurrent(TokenType.CLOSE_PAREN):
         close = CloseListNode(parent, input.current().pos)
         input.ahead()
         return close
@@ -42,7 +42,7 @@ def parseListTail(input, parent):
     if input.hasCurrent() and input.hasMore():
         assertToken(TokenType.COMMA, input)
         input.ahead()
-        expr = rollup(parseExpression)(input, parent)
+        expr = greedy(parseExpression)(input, parent)
         if expr is not None:
             item = ListItemNode(expr, parent, expr.pos)
             expr.parent = item

smnp/ast/parsers/minus.py

@@ -5,10 +5,13 @@ from smnp.token.type import TokenType
 
 # minus -> '-' int
 def parseMinus(input, parent):
-    if input.current().type == TokenType.MINUS:
+    if input.isCurrent(TokenType.MINUS):
         token = input.current()
         input.ahead()
 
-        expr = parseInteger(input, parent)
+        if input.hasCurrent():
+            expr = parseInteger(input, parent)
 
-        return IntegerLiteralNode(-expr.value, parent, token.pos)
+            return IntegerLiteralNode(-expr.value, parent, token.pos)
+
+    return None

smnp/ast/parsers/note.py

@@ -7,7 +7,7 @@ from smnp.token.type import TokenType
 
 # note -> NOTE
 def parseNote(input, parent):
-    if input.current().type == TokenType.NOTE:
+    if input.isCurrent(TokenType.NOTE):
         token = input.current()
         value = token.value
         consumedChars = 1

smnp/ast/parsers/ret.py

@@ -4,7 +4,7 @@ from smnp.token.type import TokenType
 
 
 def parseReturn(input, parent):
-    if input.current().type == TokenType.RETURN:
+    if input.isCurrent(TokenType.RETURN):
         token = input.current()
         input.ahead()
 

smnp/ast/parsers/string.py

@@ -4,7 +4,7 @@ from smnp.token.type import TokenType
 
 # string -> STRING
 def parseString(input, parent):
-    if input.current().type == TokenType.STRING:
+    if input.isCurrent(TokenType.STRING):
         string = StringLiteralNode(input.current().value[1:len(input.current().value) - 1], parent, input.current().pos)
         input.ahead()
 

smnp/ast/tools.py

@@ -2,7 +2,7 @@ from smnp.ast.node.model import Node
 from smnp.error.syntax import SyntaxException
 
 
-def rollup(parser):
+def greedy(parser):
     def _rollup(input, parent):
         node = Node(None, (-1, -1))
         elem = parser(input, node)

smnp/environment/environment.py

@@ -13,7 +13,7 @@ class Environment():
     def invokeMethod(self, name, object, args):
         for method in self.methods: # TODO to działa tylko dla wbudowanych funkcji
             if method.name == name:
-                ret = method.call(self, [object, *args])
+                ret = method.call(self, [object, *args.value])
                 if ret is not None:
                     return ret
         raise MethodNotFoundException(object.type, name) # TODO method not found

smnp/main.py

@@ -1,8 +1,8 @@
 import sys
 
-from smnp.ast.parser import parse
 from smnp.environment.factory import createEnvironment
 from smnp.error.base import SmnpException
+from smnp.newast.node.program import Program
 from smnp.runtime.evaluator import evaluate
 from smnp.token.tokenizer import tokenize
 
@@ -14,8 +14,10 @@ def main():
 
         tokens = tokenize(lines)
 
-        ast = parse(tokens)
+        ast = Program.parse(tokens)
+        ast.node.print()
 
+        sys.exit(0)
         env = createEnvironment()
 
         evaluate(ast, env)

smnp/newast/node/expression.py

@@ -0,0 +1,37 @@
+from smnp.newast.node.model import Node
+from smnp.newast.node.none import NoneNode
+from smnp.newast.parser import Parser
+
+
+class ExpressionNode(Node):
+    def __init__(self, pos):
+        super().__init__(pos, [NoneNode()])
+
+    @property
+    def value(self):
+        return self[0]
+
+
+    @value.setter
+    def value(self, v):
+        self[0] = v
+
+
+    @classmethod
+    def withValue(cls, pos, v):
+        node = cls(pos)
+        node.value = v
+        return node
+
+
+    @classmethod
+    def _parse(cls, input):
+        from smnp.newast.node.integer import IntegerLiteralNode
+        from smnp.newast.node.string import StringLiteralNode
+        from smnp.newast.node.list import ListNode
+
+        return Parser.oneOf(
+            IntegerLiteralNode.parse,
+            StringLiteralNode.parse,
+            ListNode.parse
+        )(input)

smnp/newast/node/ignore.py

@@ -0,0 +1,6 @@
+from smnp.newast.node.model import Node
+
+
+class IgnoredNode(Node):
+    def __init__(self, pos):
+        super().__init__(pos)

smnp/newast/node/integer.py

@@ -0,0 +1,11 @@
+from smnp.newast.node.expression import ExpressionNode
+from smnp.newast.parser import Parser
+from smnp.token.type import TokenType
+
+
+class IntegerLiteralNode(ExpressionNode):
+
+    @classmethod
+    def _parse(cls, input):
+        createNode = lambda v, pos: IntegerLiteralNode.withValue(pos, v)
+        return Parser.terminalParser(TokenType.INTEGER, createNode)(input)

smnp/newast/node/list.py

@@ -0,0 +1,102 @@
+from smnp.newast.node.expression import ExpressionNode
+from smnp.newast.node.model import Node
+from smnp.newast.node.none import NoneNode
+from smnp.newast.parser import Parser
+from smnp.token.type import TokenType
+
+
+class ListTailNode(ExpressionNode):
+    def __init__(self, pos):
+        super().__init__(pos)
+
+        self.children.append(NoneNode())
+
+    @property
+    def next(self):
+        return self[1]
+
+    @next.setter
+    def next(self, value):
+        self[1] = value
+
+    @classmethod
+    def _parse(cls, input):
+        return Parser.oneOf(
+            ListTailNode._parser1(),
+            ListTailNode._parser2(),
+        )(input)
+
+    # listTail := ']'
+    @staticmethod
+    def _parser1():
+        return Parser.terminalParser(TokenType.CLOSE_PAREN)
+
+    # listTail := ',' expr listTail
+    @staticmethod
+    def _parser2():
+        def createNode(comma, expr, listTail):
+            node = ListTailNode(expr.pos)
+            node.value = expr
+            node.next = listTail
+            return node
+
+        return Parser.allOf(
+            Parser.terminalParser(TokenType.COMMA),
+            ExpressionNode.parse,
+            ListTailNode.parse,
+            createNode=createNode
+        )
+
+
+class ListNode(ExpressionNode):
+    def __init__(self, pos):
+        super().__init__(pos)
+
+        self.children.append(NoneNode())
+
+    @property
+    def next(self):
+        return self[1]
+
+    @next.setter
+    def next(self, value):
+        self[1] = value
+
+    @classmethod
+    def _parse(cls, input):
+        return Parser.oneOf(
+            ListNode._parser1(),
+            ListNode._parser2()
+        )(input)
+
+    # list := '[' ']'
+    @staticmethod
+    def _parser1():
+        def emptyList(openParen, closeParen):
+            node = ListNode(openParen.pos)
+            node.value = openParen
+            node.next = closeParen
+            return node
+
+        return Parser.allOf(
+            Parser.terminalParser(TokenType.OPEN_PAREN),
+            Parser.terminalParser(TokenType.CLOSE_PAREN),
+            createNode=emptyList
+        )
+
+
+    # '[' expr listTail
+    @staticmethod
+    def _parser2():
+        def createNode(openParen, expr, listTail):
+            node = ListNode(openParen.pos)
+            node.value = expr
+            node.next = listTail
+            return node
+
+        return Parser.allOf(
+            Parser.terminalParser(TokenType.OPEN_PAREN, lambda v, pos: Node(pos)),
+            ExpressionNode.parse,
+            ListTailNode.parse,
+            createNode=createNode
+        )

smnp/newast/node/model.py

@@ -0,0 +1,75 @@
+class Node:
+    def __init__(self, pos, children=None):
+        if children is None:
+            children = []
+        self.children = children
+        self.pos = pos
+        self.parent = None
+        for child in self.children:
+            if isinstance(child, Node):
+                child.parent = self
+
+    def __len__(self):
+        return len(self.children)
+
+    def __getitem__(self, key):
+        return self.children[key]
+
+    def __setitem__(self, key, value):
+        if isinstance(value, Node):
+            value.parent = self
+        self.children[key] = value
+
+    def append(self, node):
+        if isinstance(node, Node):
+            node.parent = self
+        self.children.append(node)
+
+    def pop(self, index):
+        return self.children.pop(index)
+
+    @classmethod
+    def _parse(cls, input):
+        pass
+
+    @classmethod
+    def parse(cls, input):
+        result = cls._parse(input)
+        if result is None:
+            return ParseResult.FAIL()
+
+        if not isinstance(result, ParseResult):
+            raise RuntimeError(f"_parse() method of '{cls.__name__}' class haven't returned ParseResult object")
+
+        return result
+
+    def print(self):
+        self._print(first=True)
+
+    def _print(self, prefix="", last=True, first=False):
+        print(prefix, '' if first else '└─' if last else '├─', self.__class__.__name__, sep="")
+        prefix += '   ' if last else '│  '
+        for i, child in enumerate(self.children):
+            last = i == len(self.children) - 1
+            if isinstance(child, Node):
+                child._print(prefix, last)
+            else:
+                print(prefix, '└' if last else '├', f"'{str(child)}'", sep="")
+
+
+class ParseResult():
+    def __init__(self, result, node):
+        if result and node is None:
+            raise RuntimeError("Node musn't be None if result is set to True for ParseResult")
+        self.result = result
+        self.node = node
+
+    @staticmethod
+    def FAIL():
+        return ParseResult(False, None)
+
+    @staticmethod
+    def OK(node):
+        return ParseResult(True, node)
+
+

smnp/newast/node/none.py

@@ -0,0 +1,9 @@
+from smnp.newast.node.model import Node
+
+
+class NoneNode(Node):
+    def __init__(self):
+        super().__init__((-1, -1))
+
+    def _parse(self, input):
+        pass

smnp/newast/node/program.py

@@ -0,0 +1,24 @@
+from smnp.error.syntax import SyntaxException
+from smnp.newast.node.expression import ExpressionNode
+from smnp.newast.node.model import Node, ParseResult
+from smnp.newast.parser import Parser
+
+
+class Program(Node):
+    def __init__(self):
+        super().__init__((-1, -1))
+
+    @classmethod
+    def _parse(cls, input):
+        def parseToken(input):
+            return Parser.oneOf(
+                ExpressionNode.parse,
+                exception = SyntaxException("Unknown statement")
+            )(input)
+
+        root = Program()
+        while input.hasCurrent():
+            result = parseToken(input)
+            if result.result:
+                root.append(result.node)
+        return ParseResult.OK(root)

smnp/newast/node/string.py

@@ -0,0 +1,11 @@
+from smnp.newast.node.expression import ExpressionNode
+from smnp.newast.parser import Parser
+from smnp.token.type import TokenType
+
+
+class StringLiteralNode(ExpressionNode):
+
+    @classmethod
+    def _parse(cls, input):
+        createNode = lambda v, pos: StringLiteralNode.withValue(pos, v[1:len(v)-1])
+        return Parser.terminalParser(TokenType.STRING, createNode)(input)

smnp/newast/parser.py

@@ -0,0 +1,75 @@
+from smnp.newast.node.ignore import IgnoredNode
+from smnp.newast.node.model import ParseResult
+
+
+class Parser:
+
+    @staticmethod
+    def nonTerminalParser(parser, createNode):
+        def parse(input):
+            token = input.current()
+            result = parse(input)
+            if result.result:
+                return ParseResult.OK(createNode(result.node, token.pos))
+            return ParseResult.FAIL()
+        return parse
+
+    @staticmethod
+    def terminalParser(expectedType, createNode=None):
+        def provideNode(value, pos):
+            if createNode is None:
+                return IgnoredNode(pos)
+            return createNode(value, pos)
+
+        def parse(input):
+            if input.hasCurrent() and input.current().type == expectedType:
+                token = input.current()
+                input.ahead()
+                return ParseResult.OK(provideNode(token.value, token.pos))
+            return ParseResult.FAIL()
+
+        return parse
+
+    @staticmethod
+    def oneOf(*parsers, exception=None):
+        def combinedParser(input):
+            snap = input.snapshot()
+            for parser in parsers:
+                value = parser(input)
+                if value.result:
+                    return value
+
+            if exception is not None:
+                raise exception
+
+            input.reset(snap)
+            return ParseResult.FAIL()
+
+        return combinedParser
+    @staticmethod
+    def allOf(*parsers, createNode, exception=None):
+        if len(parsers) == 0:
+            raise RuntimeError("Pass one parser at least")
+
+        def extendedParser(input):
+            snap = input.snapshot()
+
+            results = []
+
+            for parser in parsers:
+                result = parser(input)
+
+                if not result.result:
+                    if exception is not None:
+                        raise exception
+
+                    input.reset(snap)
+                    return ParseResult.FAIL()
+
+                results.append(result.node)
+
+            return ParseResult.OK(createNode(*results))
+
+
+
+        return extendedParser

smnp/newast/tools.py

@@ -0,0 +1,8 @@
+from smnp.error.syntax import SyntaxException
+
+
+def assertToken(expected, input):
+    if not input.hasCurrent():
+        raise SyntaxException(f"Expected '{expected}'")
+    if expected != input.current().type:
+        raise SyntaxException(f"Expected '{expected}', found '{input.current().value}'", input.current().pos)

smnp/runtime/evaluators/access.py

@@ -1,33 +1,42 @@
+from smnp.ast.node.access import AccessNode
+from smnp.ast.node.function import FunctionCallNode
+from smnp.error.base import SmnpException
 from smnp.error.runtime import RuntimeException
+from smnp.runtime.evaluator import evaluate
 from smnp.runtime.evaluators.list import evaluateList
 
 
 def evaluateAccess(access, environment):
-    pass
-    #element = evaluate(access.element, environment)
-    # TODO: narazie tylko metody działają
-    #e = evaluateMethodCall(element, access.property, environment)
+    element = evaluate(access.element, environment)
+    if type(access.property) == FunctionCallNode:
+        return evaluateMethodCall(element, access.property, environment)
+    if type(access.property) == AccessNode:
+        return evaluateAccess(access.property, environment)
+
+    raise RuntimeException("Not implemented yet", access.property.pos)
+    # TODO only methods can be handled so far
 
 
+def evaluateMethodCall(element, methodCall, environment):
+    try:
+        methodName = methodCall.identifier.identifier
+        arguments = evaluateList(methodCall.arguments, environment)
 
-def evaluateMethodCall(element, functionCall, environment):
-    funcName = functionCall.identifier.identifier
-    arguments = evaluateList(functionCall.arguments, environment)
-    arguments.insert(0, element)
-    # for name, library in environment.customFunctions.items():
-    # if funcName == name:
-    # if len(library['params']) != len(arguments):
-    # raise RuntimeException(functionCall.pos, f"Calling '{funcName}' requires {len(library['params'])} and {len(arguments)} was passed")
-    # environment.scopes.append({ library['params'][i].identifier: v for i, v in enumerate(arguments) })
-    # returnValue = None
-    # for node in library['body']:
-    # if not isinstance(node, ReturnNode):
-    # evaluate(node, environment)
-    # else:
-    # returnValue = evaluateReturn(node, environment)
-    # environment.scopes.pop(-1)
-    # return returnValue
-    for name, definition in environment.methods[type(element)].items():
-        if name == funcName:
-            return definition(arguments, environment)
-    raise RuntimeException(f"Method '{funcName}' does not exist", functionCall.pos)
+        return environment.invokeMethod(methodName, element, arguments)
+
+    except SmnpException as e:
+        e.pos = methodCall.pos
+        raise e
+# for name, library in environment.customFunctions.items():
+# if funcName == name:
+# if len(library['params']) != len(arguments):
+# raise RuntimeException(functionCall.pos, f"Calling '{funcName}' requires {len(library['params'])} and {len(arguments)} was passed")
+# environment.scopes.append({ library['params'][i].identifier: v for i, v in enumerate(arguments) })
+# returnValue = None
+# for node in library['body']:
+# if not isinstance(node, ReturnNode):
+# evaluate(node, environment)
+# else:
+# returnValue = evaluateReturn(node, environment)
+# environment.scopes.pop(-1)
+# return returnValue

smnp/token/model.py

@@ -25,7 +25,10 @@ class TokenList:
         if self.cursor >= len(self.tokens):
             raise RuntimeError(f"Cursor points to not existing token! Cursor = {self.cursor}, len = {len(self.tokens)}")
         return self.tokens[self.cursor]
-    
+
+    def isCurrent(self, type):
+        return self.hasCurrent() and self.current().type == type
+
     def next(self, number=1):
         return self.tokens[self.cursor + number]
     
@@ -42,14 +45,13 @@ class TokenList:
         self.cursor += 1        
     
     def snapshot(self):
-        self.snapshot = self.cursor
+        return self.cursor
         
-    def reset(self):
-        self.cursor = self.snapshot
-        return self.tokens[self.cursor]
+    def reset(self, snap):
+        self.cursor = snap
     
     def __str__(self):
-        return f"[Cursor: {self.cursor}\n{', '.join([str(token) for token in self.tokens])}]"
+        return f"[Current({self.cursor}): {self.current() if self.hasCurrent() else 'out of tokens'}\n{', '.join([str(token) for token in self.tokens])}]"
     
     def __repr__(self):
         return self.__str__()