4 files changed, 647 insertions, 0 deletions
diff --git a/src/lexer.py b/src/lexer.py
new file mode 100644
index 0000000..e4c26ce
--- /dev/null
+++ b/src/lexer.py
@@ -0,0 +1,202 @@
+# Copyright 2015 Egor Tensin <Egor.Tensin@gmail.com>
+# This file is licensed under the terms of the MIT License.
+# See LICENSE.txt for details.
+
+import re
+
+from tokens import *
+
+class LexerError(RuntimeError):
+    pass 
+
+class Lexer:
+    def __init__(self, src_file):
+        self._line_buf = ''
+        self._tok_buf = []
+        self._src_file = src_file
+        self._ws_re = re.compile(r'^\s+')
+        self._identifier_re = re.compile(r'^[^\W\d]\w*')
+        self._const_toks = {
+            '+': AdditionOpToken,
+            '-': SubtractionOpToken,
+            '*': MultiplicationOpToken,
+            '/': DivisionOpToken,
+            ':=': AssignmentOpToken,
+            ';': SemicolonToken,
+            '(': OpeningParenToken,
+            ')': ClosingParenToken,
+            '{': OpeningBraceToken,
+            '}': ClosingBraceToken,
+            '&&': AndOpToken,
+            '||': OrOpToken,
+            '==': EqualsOpToken,
+            '!=': NotEqualsOpToken,
+        }
+        self._const_toks_sorted = list(self._const_toks.keys())
+        self._const_toks_sorted.sort()
+        self._make_sure_const_tokens_dont_match_identifier_re()
+        self._keywords = {
+            'if': IfToken,
+            'print': PrintToken,
+            'True': TrueToken,
+            'False': FalseToken,
+        }
+        self._make_sure_keywords_match_identifier_re()
+
+    def _make_sure_keywords_match_identifier_re(self):
+        for kw in self._keywords:
+            if not re.match(self._identifier_re, kw):
+                raise LexerError("keyword '%s' is not an identifier" % (kw))
+
+    def _make_sure_const_tokens_dont_match_identifier_re(self):
+        for t in self._const_toks_sorted:
+            if re.match(self._identifier_re, t):
+                raise LexerError("const token '%s' is an identifier" % (t))
+
+    def _try_require_line_buf(self):
+        if self._line_buf:
+            return True
+        if self._src_file is None:
+            return False
+        self._line_buf = self._src_file.readline()
+        if not self._line_buf:
+            self._src_file = None
+            return False
+        return True
+
+    def _eat_number_after_e_sign(self, acc):
+        m_after_e_sign = re.match(r'^[\-+]?\d+', self._line_buf)
+        if m_after_e_sign:
+            after_e_sign = m_after_e_sign.group(0)
+            self._line_buf = self._line_buf[len(after_e_sign):]
+            return FloatingPointNumberToken('%s%s' % (acc, after_e_sign))
+        raise LexerError("'%c' unexpected" % (self._line_buf[0]))
+
+    def _eat_number_after_dec_mark(self, acc):
+        if not self._line_buf:
+            return FloatingPointNumberToken(acc)
+        m_digits = re.match(r'^\d+', self._line_buf)
+        if m_digits:
+            digits = m_digits.group(0)
+            self._line_buf = self._line_buf[len(digits):]
+            return self._eat_number_after_dec_mark('%s%s' % (acc, digits))
+        m_e_sign = re.match(r'^[eE]', self._line_buf)
+        if m_e_sign:
+            e_sign = m_e_sign.group(0)
+            self._line_buf = self._line_buf[len(e_sign):]
+            return self._eat_number_after_e_sign('%s%s' % (acc, e_sign))
+        return FloatingPointNumberToken(acc)
+
+    def _eat_number_after_first_digit(self, acc):
+        if not self._line_buf:
+            return IntegerNumberToken(acc)
+        m_digits = re.match(r'^\d+', self._line_buf)
+        if m_digits:
+            digits = m_digits.group(0)
+            self._line_buf = self._line_buf[len(digits):]
+            return self._eat_number_after_first_digit('%s%s' % (acc, digits))
+        m_e_sign = re.match(r'^[eE]', self._line_buf)
+        if m_e_sign:
+            e_sign = m_e_sign.group(0)
+            self._line_buf = self._line_buf[len(e_sign):]
+            return self._eat_number_after_e_sign('%s%s' % (acc, e_sign))
+        m_dec_mark = re.match(r'^\.', self._line_buf)
+        if m_dec_mark:
+            dec_mark = m_dec_mark.group(0)
+            self._line_buf = self._line_buf[len(dec_mark):]
+            return self._eat_number_after_dec_mark('%s%s' % (acc, dec_mark))
+        return IntegerNumberToken(acc)
+
+    def _try_eat_number(self):
+        m_first_digit = re.match(r'^\d', self._line_buf)
+        if m_first_digit:
+            first_digit = m_first_digit.group(0)
+            self._line_buf = self._line_buf[len(first_digit):]
+            return self._eat_number_after_first_digit(first_digit)
+        m_dec_mark = re.match(r'^\.\d', self._line_buf)
+        if m_dec_mark:
+            dec_mark = m_dec_mark.group(0)
+            self._line_buf = self._line_buf[len(dec_mark):]
+            return self._eat_number_after_dec_mark(dec_mark)
+        return False
+
+    def _try_eat_ws(self):
+        while True:
+            if not self._try_require_line_buf():
+                return False
+            m_ws = re.match(self._ws_re, self._line_buf)
+            if not m_ws:
+                return True
+            self._line_buf = self._line_buf[len(m_ws.group(0)):]
+        return True
+
+    def _try_eat_identifier_or_keyword(self):
+        m_identifier = re.match(self._identifier_re, self._line_buf)
+        if m_identifier:
+            identifier = m_identifier.group(0)
+            self._line_buf = self._line_buf[len(identifier):]
+            if identifier in self._keywords:
+                return self._keywords[identifier]()
+            else:
+                return IdentifierToken(identifier)
+        return False
+
+    def _try_eat_const_token(self):
+        for t in self._const_toks_sorted:
+            if self._line_buf.startswith(t):
+                self._line_buf = self._line_buf[len(t):]
+                return self._const_toks[t]()
+        return False
+
+    def _try_eat_token(self):
+        if not self._try_eat_ws():
+            return False
+        const_tok = self._try_eat_const_token()
+        if const_tok:
+            self._tok_buf.append(const_tok)
+            return const_tok
+        identifier_or_keyword = self._try_eat_identifier_or_keyword()
+        if identifier_or_keyword:
+            self._tok_buf.append(identifier_or_keyword)
+            return identifier_or_keyword
+        number = self._try_eat_number()
+        if number:
+            self._tok_buf.append(number)
+            return number
+        raise LexerError("'%c' unexpected" % (self._line_buf[0]))
+
+    def _try_require_tok_buf(self, n = 1):
+        if n < 1:
+            raise LexerError("unable to require %d tokens" % (n))
+        while len(self._tok_buf) < n:
+            if not self._try_eat_token():
+                return False
+        return True
+
+    def has_next_token(self, n = 1):
+        return self._try_require_tok_buf(n)
+
+    def preview_next_token(self, n = 0):
+        if not self.has_next_token(n + 1):
+            raise LexerError("not enough tokens")
+        return self._tok_buf[n]
+
+    def drop_next_token(self, n = 1):
+        if not self.has_next_token(n):
+            raise LexerError("not enough tokens")
+        if n == 1:
+            return self._tok_buf.pop(0)
+        else:
+            xs = self._tok_buf[:n]
+            self._tok_buf = self._tok_buf[n:]
+            return xs
+
+if __name__ == '__main__':
+    import argparse
+    parser = argparse.ArgumentParser()
+    parser.add_argument('src_path', help='set soure file path')
+    args = parser.parse_args()
+    with open(args.src_path, 'r') as src_file:
+        lexer = Lexer(src_file)
+        while lexer.has_next_token():
+            print(lexer.drop_next_token().__class__.__name__)
diff --git a/src/nodes.py b/src/nodes.py
new file mode 100644
index 0000000..ea9517d
--- /dev/null
+++ b/src/nodes.py
@@ -0,0 +1,144 @@
+# Copyright 2015 Egor Tensin <Egor.Tensin@gmail.com>
+# This file is licensed under the terms of the MIT License.
+# See LICENSE.txt for details.
+
+class ProgramNode:
+    def __init__(self, stmt_list):
+        self._stmt_list = stmt_list
+
+    def execute(self):
+        for stmt in self._stmt_list:
+            stmt.execute()
+
+_varmap = { }
+
+class CompoundStatementNode:
+    def __init__(self, stmt_list):
+        self._stmt_list = stmt_list
+
+    def execute(self):
+        for stmt in self._stmt_list:
+            stmt.execute()
+
+class EmptyStatementNode:
+    def execute(self):
+        pass
+
+class AssignmentNode:
+    def __init__(self, identifier, arithm_expr):
+        self._identifier = identifier
+        self._arithm_expr = arithm_expr
+
+    def execute(self):
+        _varmap[str(self._identifier)] = self._arithm_expr.execute()
+        return None
+
+class PrintStatementNode:
+    def __init__(self, arithm_expr):
+        self._arithm_expr = arithm_expr
+
+    def execute(self):
+        print(self._arithm_expr.execute())
+        return None
+
+class IdentifierNode:
+    def __init__(self, identifier):
+        self._identifier = identifier
+
+    def execute(self):
+        return _varmap[str(self._identifier)]
+
+class AdditionOpNode:
+    def __init__(self, left, right):
+        self._left = left
+        self._right = right
+
+    def execute(self):
+        return self._left.execute() + self._right.execute()
+
+class SubtractionOpNode:
+    def __init__(self, left, right):
+        self._left = left
+        self._right = right
+
+    def execute(self):
+        return self._left.execute() + self._right.execute()
+
+class MultiplicationOpNode:
+    def __init__(self, left, right):
+        self._left = left
+        self._right = right
+
+    def execute(self):
+        return self._left.execute() * self._right.execute()
+
+class DivisionOpNode:
+    def __init__(self, left, right):
+        self._left = left
+        self._right = right
+
+    def execute(self):
+        return self._left.execute() / self._right.execute()
+
+class IntegerNumberNode:
+    def __init__(self, n):
+        self._n = n
+
+    def execute(self):
+        return int(self._n)
+
+class FloatingPointNumberNode:
+    def __init__(self, n):
+        self._n = n
+
+    def execute(self):
+        return float(self._n)
+
+class IfStatementNode:
+    def __init__(self, cond, body):
+        self._cond = cond
+        self._body = body
+
+    def execute(self):
+        if self._cond.execute():
+            return self._body.execute()
+
+class TrueNode:
+    def execute(self):
+        return True
+
+class FalseNode:
+    def execute(self):
+        return False
+
+class AndOpNode:
+    def __init__(self, left, right):
+        self._left = left
+        self._right = right
+
+    def execute(self):
+        return self._left.execute() and self._right.execute()
+
+class OrOpNode:
+    def __init__(self, left, right):
+        self._left = left
+        self._right = right
+
+    def execute(self):
+        return self._left.execute() or self._right.execute()
+
+class EqualsOpNode:
+    def __init__(self, left, right):
+        self._left = left
+        self._right = right
+
+    def execute(self):
+        return self._left.execute() == self._right.execute()
+
+class NotEqualsOpNode:
+    def __init__(self, left, right):
+        self._left = left
+        self._right = right
+
+    def execute(self):
+        return self._left.execute() != self._right.execute()
diff --git a/src/parser.py b/src/parser.py
new file mode 100644
index 0000000..5ee5207
--- /dev/null
+++ b/src/parser.py
@@ -0,0 +1,196 @@
+# Copyright 2015 Egor Tensin <Egor.Tensin@gmail.com>
+# This file is licensed under the terms of the MIT License.
+# See LICENSE.txt for details.
+
+from lexer import *
+from nodes import *
+
+class ParserError(RuntimeError):
+    pass
+
+class Parser:
+    def __init__(self, src_file):
+        self._lexer = Lexer(src_file)
+
+    def parse(self):
+        return self._parse_program()
+
+    def _try_parse_token(self, cls):
+        if not self._lexer.has_next_token():
+            return False
+        t = self._lexer.preview_next_token()
+        if not isinstance(t, cls):
+            return False
+        self._lexer.drop_next_token()
+        return t
+
+    def _parse_token(self, cls):
+        if not self._lexer.has_next_token():
+            raise ParserError("%s expected" % cls.__name__)
+        t = self._lexer.preview_next_token()
+        if not isinstance(t, cls):
+            raise ParserError("%s expected instead of %s" % (
+                    cls.__name__, t.__class__.__name__))
+        self._lexer.drop_next_token()
+        return t
+
+    def _parse_program(self):
+        stmt_list = []
+        while self._lexer.has_next_token():
+            stmt = self._try_parse_stmt()
+            if not stmt:
+                raise ParserError("unexpected token '%s'" % (
+                        self._lexer.preview_next_token()))
+            stmt_list.append(stmt)
+        return ProgramNode(stmt_list)
+
+    def _try_parse_stmt(self):
+        print_stmt = self._try_parse_print_stmt()
+        if print_stmt:
+            return print_stmt
+        assignment = self._try_parse_assignment()
+        if assignment:
+            return assignment
+        empty_stmt = self._try_parse_empty_stmt()
+        if empty_stmt:
+            return empty_stmt
+        if_stmt = self._try_parse_if_stmt()
+        if if_stmt:
+            return if_stmt
+        block = self._try_parse_block()
+        if block:
+            return block
+        return False
+
+    def _try_parse_empty_stmt(self):
+        if not self._try_parse_token(SemicolonToken):
+            return False
+        return EmptyStatementNode()
+
+    def _try_parse_block(self):
+        if not self._try_parse_token(OpeningBraceToken):
+            return False
+        stmt_list = []
+        while True:
+            stmt = self._try_parse_stmt()
+            if stmt:
+                stmt_list.append(stmt)
+            else:
+                break
+        self._parse_token(ClosingBraceToken)
+        return CompoundStatementNode(stmt_list)
+
+    def _try_parse_if_stmt(self):
+        if not self._try_parse_token(IfToken):
+            return False
+        self._parse_token(OpeningParenToken)
+        cond = self._parse_logical_expr()
+        self._parse_token(ClosingParenToken)
+        stmt = self._try_parse_stmt()
+        if not stmt:
+            raise ParserError("unexpected token '%s'" % (
+                    self._lexer.preview_next_token()))
+        return IfStatementNode(cond, stmt)
+
+    def _try_parse_print_stmt(self):
+        if not self._try_parse_token(PrintToken):
+            return False
+        arithm_expr = self._parse_arithm_expr()
+        self._parse_token(SemicolonToken)
+        return PrintStatementNode(arithm_expr)
+
+    def _try_parse_assignment(self):
+        if not self._lexer.has_next_token(2):
+            return False
+        identifier = self._lexer.preview_next_token(0)
+        if not isinstance(identifier, IdentifierToken):
+            return False
+        op = self._lexer.preview_next_token(1)
+        if not isinstance(op, AssignmentOpToken):
+            return False
+        self._lexer.drop_next_token(2)
+        arithm_expr = self._parse_arithm_expr()
+        self._parse_token(SemicolonToken)
+        return AssignmentNode(identifier, arithm_expr)
+
+    def _parse_logical_expr(self):
+        left = self._parse_logical_term()
+        while self._lexer.has_next_token():
+            if self._try_parse_token(AndOpToken):
+                left = AndOpNode(left, self._parse_logical_term())
+            elif self._try_parse_token(OrOpToken):
+                left = OrOpNode(left, self._parse_logical_term())
+            else:
+                return left
+        return left
+
+    def _parse_logical_term(self):
+        left = self._parse_logical_factor()
+        if self._lexer.has_next_token():
+            if self._try_parse_token(EqualsOpToken):
+                left = EqualsOpNode(left, self._parse_logical_factor())
+            elif self._try_parse_token(NotEqualsOpToken):
+                left = NotEqualsOpNode(left, self._parse_logical_factor())
+            else:
+                return left
+        return left
+
+    def _parse_logical_factor(self):
+        if self._try_parse_token(TrueToken):
+            return TrueNode()
+        elif self._try_parse_token(FalseToken):
+            return FalseNode()
+        elif self._try_parse_token(OpeningParenToken):
+            logical_expr = self._parse_logical_expr()
+            self._parse_token(ClosingParenToken)
+            return logical_expr
+        else:
+            raise ParserError('expected \'True\', \'False\' or \'(\'')
+
+    def _parse_arithm_expr(self):
+        left = self._parse_arithm_term()
+        while self._lexer.has_next_token():
+            if self._try_parse_token(AdditionOpToken):
+                left = AdditionOpNode(left, self._parse_arithm_term())
+            elif self._try_parse_token(SubtractionOpToken):
+                left = SubtractionOpNode(left, self._parse_arithm_term())
+            else:
+                return left
+        return left
+
+    def _parse_arithm_term(self):
+        left = self._parse_arithm_factor()
+        while self._lexer.has_next_token():
+            if self._try_parse_token(MultiplicationOpToken):
+                left = MultiplicationOpNode(left, self._parse_arithm_factor())
+            elif self._try_parse_token(DivisionOpToken):
+                left = DivisionOpNode(left, self._parse_arithm_factor())
+            else:
+                return left
+        return left
+        
+    def _parse_arithm_factor(self):
+        identifier = self._try_parse_token(IdentifierToken)
+        if identifier:
+            return IdentifierNode(identifier)
+        int_num = self._try_parse_token(IntegerNumberToken)
+        if int_num:
+            return IntegerNumberNode(int_num)
+        float_num = self._try_parse_token(FloatingPointNumberToken)
+        if float_num:
+            return FloatingPointNumberNode(float_num)
+        if self._try_parse_token(OpeningParenToken):
+            arithm_expr = self._parse_arithm_expr()
+            self._parse_token(ClosingParenToken)
+            return arithm_expr
+        else:
+            raise ParserError('expected an identifier, a number or \'(\'')
+
+if __name__ == '__main__':
+    import argparse
+    parser = argparse.ArgumentParser()
+    parser.add_argument('src_path', help='set source file path')
+    args = parser.parse_args()
+    with open(args.src_path, 'r') as src_file:
+        parser = Parser(src_file)
+        parser.parse().execute()
diff --git a/src/tokens.py b/src/tokens.py
new file mode 100644
index 0000000..3c04668
--- /dev/null
+++ b/src/tokens.py
@@ -0,0 +1,105 @@
+# Copyright 2015 Egor Tensin <Egor.Tensin@gmail.com>
+# This file is licensed under the terms of the MIT License.
+# See LICENSE.txt for details.
+
+class Token:
+    pass
+
+class AdditionOpToken(Token):
+    def __str__(self):
+        return '+'
+
+class SubtractionOpToken(Token):
+    def __str__(self):
+        return '-'
+
+class MultiplicationOpToken(Token):
+    def __str__(self):
+        return '*'
+
+class DivisionOpToken(Token):
+    def __str__(self):
+        return '/'
+
+class AssignmentOpToken(Token):
+    def __str__(self):
+        return ':='
+
+class SemicolonToken(Token):
+    def __str__(self):
+        return ';'
+
+class PrintToken(Token):
+    def __str__(self):
+        return 'print'
+
+class OpeningParenToken(Token):
+    def __str__(self):
+        return '('
+
+class ClosingParenToken(Token):
+    def __str__(self):
+        return ')'
+
+class OpeningBraceToken(Token):
+    def __str__(self):
+        return '{'
+
+class ClosingBraceToken(Token):
+    def __str__(self):
+        return '}'
+
+class IdentifierToken(Token):
+    def __init__(self, i):
+        self._i = i
+
+    def __str__(self):
+        return str(self._i)
+
+class FloatingPointNumberToken(Token):
+    def __init__(self, n):
+        self._n = n
+
+    def __float__(self):
+        return float(self._n)
+
+    def __str__(self):
+        return str(self._n)
+
+class IntegerNumberToken(Token):
+    def __init__(self, n):
+        self._n = n
+
+    def __int__(self):
+        return int(self._n)
+
+    def __str__(self):
+        return str(self._n)
+
+class TrueToken(Token):
+    def __str__(self):
+        return 'True'
+
+class FalseToken(Token):
+    def __str__(self):
+        return 'False'
+
+class AndOpToken(Token):
+    def __str__(self):
+        return '&&'
+
+class OrOpToken(Token):
+    def __str__(self):
+        return '||'
+
+class IfToken(Token):
+    def __str__(self):
+        return 'if'
+
+class EqualsOpToken(Token):
+    def __str__(self):
+        return '=='
+
+class NotEqualsOpToken(Token):
+    def __str__(self):
+        return '!='