Part 10

README.md

@@ -9,3 +9,4 @@ Source code for the series **Let's Build A Simple Interpreter**
 + [Let's Build A Simple Interpreter. Part 7.](http://ruslanspivak.com/lsbasi-part7/)
 + [Let's Build A Simple Interpreter. Part 8.](http://ruslanspivak.com/lsbasi-part8/)
 + [Let's Build A Simple Interpreter. Part 9.](http://ruslanspivak.com/lsbasi-part9/)
++ [Let's Build A Simple Interpreter. Part 10.](http://ruslanspivak.com/lsbasi-part10/)

part10/python/genastdot.py

@@ -0,0 +1,169 @@
+###############################################################################
+#  AST visualizer - generates a DOT file for Graphviz.                        #
+#                                                                             #
+#  To generate an image from the DOT file run $ dot -Tpng -o ast.png ast.dot  #
+#                                                                             #
+###############################################################################
+import argparse
+import textwrap
+
+from spi import Lexer, Parser, NodeVisitor
+
+
+class ASTVisualizer(NodeVisitor):
+    def __init__(self, parser):
+        self.parser = parser
+        self.ncount = 1
+        self.dot_header = [textwrap.dedent("""\
+        digraph astgraph {
+          node [shape=circle, fontsize=12, fontname="Courier", height=.1];
+          ranksep=.3;
+          edge [arrowsize=.5]
+
+        """)]
+        self.dot_body = []
+        self.dot_footer = ['}']
+
+    def visit_Program(self, node):
+        s = '  node{} [label="Program"]\n'.format(self.ncount)
+        self.dot_body.append(s)
+        node._num = self.ncount
+        self.ncount += 1
+
+        self.visit(node.block)
+
+        s = '  node{} -> node{}\n'.format(node._num, node.block._num)
+        self.dot_body.append(s)
+
+    def visit_Block(self, node):
+        s = '  node{} [label="Block"]\n'.format(self.ncount)
+        self.dot_body.append(s)
+        node._num = self.ncount
+        self.ncount += 1
+
+        for declaration in node.declarations:
+            self.visit(declaration)
+        self.visit(node.compound_statement)
+
+        for decl_node in node.declarations:
+            s = '  node{} -> node{}\n'.format(node._num, decl_node._num)
+            self.dot_body.append(s)
+
+        s = '  node{} -> node{}\n'.format(
+            node._num,
+            node.compound_statement._num
+        )
+        self.dot_body.append(s)
+
+    def visit_VarDecl(self, node):
+        s = '  node{} [label="VarDecl"]\n'.format(self.ncount)
+        self.dot_body.append(s)
+        node._num = self.ncount
+        self.ncount += 1
+
+        self.visit(node.var_node)
+        s = '  node{} -> node{}\n'.format(node._num, node.var_node._num)
+        self.dot_body.append(s)
+
+        self.visit(node.type_node)
+        s = '  node{} -> node{}\n'.format(node._num, node.type_node._num)
+        self.dot_body.append(s)
+
+    def visit_Type(self, node):
+        s = '  node{} [label="{}"]\n'.format(self.ncount, node.token.value)
+        self.dot_body.append(s)
+        node._num = self.ncount
+        self.ncount += 1
+
+    def visit_Num(self, node):
+        s = '  node{} [label="{}"]\n'.format(self.ncount, node.token.value)
+        self.dot_body.append(s)
+        node._num = self.ncount
+        self.ncount += 1
+
+    def visit_BinOp(self, node):
+        s = '  node{} [label="{}"]\n'.format(self.ncount, node.op.value)
+        self.dot_body.append(s)
+        node._num = self.ncount
+        self.ncount += 1
+
+        self.visit(node.left)
+        self.visit(node.right)
+
+        for child_node in (node.left, node.right):
+            s = '  node{} -> node{}\n'.format(node._num, child_node._num)
+            self.dot_body.append(s)
+
+    def visit_UnaryOp(self, node):
+        s = '  node{} [label="unary {}"]\n'.format(self.ncount, node.op.value)
+        self.dot_body.append(s)
+        node._num = self.ncount
+        self.ncount += 1
+
+        self.visit(node.expr)
+        s = '  node{} -> node{}\n'.format(node._num, node.expr._num)
+        self.dot_body.append(s)
+
+    def visit_Compound(self, node):
+        s = '  node{} [label="Compound"]\n'.format(self.ncount)
+        self.dot_body.append(s)
+        node._num = self.ncount
+        self.ncount += 1
+
+        for child in node.children:
+            self.visit(child)
+            s = '  node{} -> node{}\n'.format(node._num, child._num)
+            self.dot_body.append(s)
+
+    def visit_Assign(self, node):
+        s = '  node{} [label="{}"]\n'.format(self.ncount, node.op.value)
+        self.dot_body.append(s)
+        node._num = self.ncount
+        self.ncount += 1
+
+        self.visit(node.left)
+        self.visit(node.right)
+
+        for child_node in (node.left, node.right):
+            s = '  node{} -> node{}\n'.format(node._num, child_node._num)
+            self.dot_body.append(s)
+
+    def visit_Var(self, node):
+        s = '  node{} [label="{}"]\n'.format(self.ncount, node.value)
+        self.dot_body.append(s)
+        node._num = self.ncount
+        self.ncount += 1
+
+    def visit_NoOp(self, node):
+        s = '  node{} [label="NoOp"]\n'.format(self.ncount)
+        self.dot_body.append(s)
+        node._num = self.ncount
+        self.ncount += 1
+
+    def gendot(self):
+        tree = self.parser.parse()
+        self.visit(tree)
+        return ''.join(self.dot_header + self.dot_body + self.dot_footer)
+
+
+def main():
+    argparser = argparse.ArgumentParser(
+        description='Generate an AST DOT file.'
+    )
+    argparser.add_argument(
+        'fname',
+        help='Pascal source file'
+    )
+    args = argparser.parse_args()
+    fname = args.fname
+    text = open(fname, 'r').read()
+
+    lexer = Lexer(text)
+    parser = Parser(lexer)
+    viz = ASTVisualizer(parser)
+    content = viz.gendot()
+    print(content)
+
+
+if __name__ == '__main__':
+    main()

part10/python/part10.pas

@@ -0,0 +1,22 @@
+PROGRAM Part10;
+VAR
+   number     : INTEGER;
+   a, b, c, x : INTEGER;
+   y          : REAL;
+
+BEGIN {Part10}
+   BEGIN
+      number := 2;
+      a := number;
+      b := 10 * a + 10 * number DIV 4;
+      c := a - - b
+   END;
+   x := 11;
+   y := 20 / 7 + 3.14;
+   { writeln('a = ', a); }
+   { writeln('b = ', b); }
+   { writeln('c = ', c); }
+   { writeln('number = ', number); }
+   { writeln('x = ', x); }
+   { writeln('y = ', y); }
+END.  {Part10}

part10/python/part10ast.pas

@@ -0,0 +1,10 @@
+PROGRAM Part10AST;
+VAR
+   a, b : INTEGER;
+   y    : REAL;
+
+BEGIN {Part10AST}
+   a := 2;
+   b := 10 * a + 10 * a DIV 4;
+   y := 20 / 7 + 3.14;
+END.  {Part10AST}