Add part 9

Author: AlimU11

.github/workflows/python-app.yml

@@ -36,4 +36,4 @@ jobs:
         flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
     - name: Test with pytest
       run: |
-        pytest base/InterpreterTest.py
+        pytest test/InterpreterTest.py

.gitignore

@@ -8,3 +8,5 @@ obj
 .vscode
 .pytest_cache
 TestResults
+dist
+build

.pre-commit-config.yaml

@@ -18,6 +18,7 @@ repos:
     rev: v2.2.2
     hooks:
       - id: codespell
+        exclude: main.spec
 
   - repo: https://github.com/pycqa/isort
     rev: 5.10.1

README.md

@@ -1,2 +1,96 @@
-# Pascal interpreter
+# Pascal Interpreter
+
 A simple pascal interpreter based on [Let's Build a Simple Interpreter](https://github.com/rspivak/lsbasi) series by [Ruslan Spivak](https://github.com/rspivak/) with usage of [EBNF grammar tester](https://mdkrajnak.github.io/ebnftest/) by [mdkrajnak](https://github.com/mdkrajnak/), [TatSu](https://github.com/neogeny/TatSu) and [railroad diagrams](https://github.com/tabatkins/railroad-diagrams).
+
+![img.png](src/img.png)
+
+## Grammar
+
+```ebnf
+<program> ::= <compound_statement> <DOT>
+
+<compound_statement> ::= <BEGIN> <statement_list> <END>
+
+<statement_list> ::= <statement> { <SEMI> <statement_list> }*
+
+<statement> ::= <compound_statement>
+              | <assignment_statement>
+              | <empty>
+
+<assignment_statement> ::= <variable> <ASSIGN> <expression>
+
+<empty> ::= ''
+
+<factor> ::= <PLUS> <factor>
+           | <MINUS> <factor>
+           | <INTEGER>
+           | <LPAREN> <expression> <RPAREN>
+           | <variable>
+
+<expression> ::= <term> { (<PLUS> | <MINUS>) <term> }*
+
+<term> ::= <factor> { (<MUL> | <DIV>) <factor> }*
+
+<variable> ::= <ID>
+
+<ID> ::= [a-zA-Z_][a-zA-Z0-9_]*
+
+<INTEGER> ::= <digit>+
+
+<digit> ::= '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'
+
+<BEGIN> ::= 'BEGIN'
+<END> ::= 'END'
+<DOT> ::= '.'
+<SEMI> ::= ';'
+<ASSIGN> ::= ':='
+<PLUS> ::= '+'
+<MINUS> ::= '-'
+<MUL> ::= '*'
+<DIV> ::= 'DIV'
+<LPAREN> ::= '('
+<RPAREN> ::= ')'
+
+```
+
+## Diagram
+
+### Program
+
+![](src/diagram1.svg)
+
+### Compound Statement
+
+![](src/diagram2.svg)
+
+### Statement List
+
+![](src/diagram3.svg)
+
+### Statement
+
+![](src/diagram4.svg)
+
+### Assignment Statement
+
+![](src/diagram5.svg)
+
+### Variable
+
+![](src/diagram6.svg)
+
+### Empty Statement
+
+![](src/diagram7.svg)
+
+### Factor
+
+![](src/diagram8.svg)
+
+### Expression
+
+![](src/diagram9.svg)
+
+### Term
+
+![](src/diagram10.svg)

base/AST.py

@@ -0,0 +1,47 @@
+class AST(object):
+    pass
+
+
+class BinOp(AST):
+    def __init__(self, left, op, right):
+        self.left = left
+        self.token = self.op = op
+        self.right = right
+
+
+class Num(AST):
+    def __init__(self, token):
+        self.token = token
+        self.value = token.value
+
+
+class UnaryOp(AST):
+    def __init__(self, op, expr):
+        self.token = self.op = op
+        self.expr = expr
+
+
+class Compound(AST):
+    """Represents a 'BEGIN ... END' block"""
+
+    def __init__(self):
+        self.children = []
+
+
+class Assign(AST):
+    def __init__(self, left, op, right):
+        self.left = left
+        self.token = self.op = op
+        self.right = right
+
+
+class Var(AST):
+    """The Var node is constructed out of ID token."""
+
+    def __init__(self, token):
+        self.token = token
+        self.value = token.value
+
+
+class NoOp(AST):
+    pass

base/Interpreter.py

@@ -0,0 +1,62 @@
+from .Node import NodeVisitor
+from .Parser import Parser
+from .Token import RESERVED_KEYWORDS, Token
+
+
+class Interpreter(NodeVisitor):
+
+    GLOBAL_SCOPE = {}
+
+    def __init__(self, text):
+        self.parser = Parser(text)
+        Interpreter.GLOBAL_SCOPE = {}
+
+    def visit_binop(self, node):
+        if node.op.type == Token.PLUS:
+            return self.visit(node.left) + self.visit(node.right)
+        elif node.op.type == Token.MINUS:
+            return self.visit(node.left) - self.visit(node.right)
+        elif node.op.type == Token.MUL:
+            return self.visit(node.left) * self.visit(node.right)
+        elif node.op.type == RESERVED_KEYWORDS['DIV'].type:
+            return self.visit(node.left) // self.visit(node.right)
+        else:
+            raise Exception('Unknown binary operator')
+
+    def visit_num(self, node):
+        return node.value
+
+    def visit_unaryop(self, node):
+        op = node.op.type
+        if op == Token.PLUS:
+            return +self.visit(node.expr)
+        elif op == Token.MINUS:
+            return -self.visit(node.expr)
+        else:
+            raise Exception('Unknown unary operator')
+
+    def visit_compound(self, node):
+        for child in node.children:
+            self.visit(child)
+
+    def visit_assign(self, node):
+        var_name = node.left.value
+        self.GLOBAL_SCOPE[var_name] = self.visit(node.right)
+
+    def visit_var(self, node):
+        var_name = node.value
+        val = self.GLOBAL_SCOPE.get(var_name)
+        if val is None:
+            raise Exception(f'NameError: name \'{var_name}\' is not defined')
+        else:
+            return val
+
+    def visit_noop(self, node):
+        pass
+
+    def interpret(self):
+        tree = self.parser.parse()
+        if tree is None:
+            return ''
+
+        return self.visit(tree)