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POPython compiler for simple language to java vm code algorithm
 

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  1. POPython compiler for simple language to java vm code algorithm
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    <p>I have a simple language that I am trying to write a compiler for (yes it is homework) to compile a simple language I shall describe if necessary to java vm code.</p> <p>It currently works pretty well I've just hit a bump with logical AND's and OR's.</p> <p>Each work fine in a single if/while condition, but if I try and chain them things go wrong, correct me if I am wrong but I believe that AND has precedence, but I was wondering if there are logical ways of arranging them? I think is what I'm trying to ask, the java vm code output just has the compare and jump statements one after the other (which seems wrong). I realise it's quite abstract so maybe what I'm after is a pseudo code/algorithm for how to structure chained AND's and OR's. </p> <p><strong>EDIT</strong>: Currently just treats any combination of AND and OR as AND's. Comparing the factor/term/expression connection (compared to booleanfactor etc) I believe that AND has precedence? Just a thought.</p> <p>Apologies if this is poorly understood :/</p> <p>So i figure ill include relevant info just incase.</p> <p>compiler </p> <pre><code>import re import sys # Restrictions: # Integer constants must be short. # Stack size must not exceed 1024. # Integer is the only type. # Logical operators cannot be nested. class Scanner: '''The interface comprises the methods lookahead and consume. Other methods should not be called from outside of this class.''' def __init__(self, input_file): '''Reads the whole input_file to input_string.''' # source code of the program to be compiled self.input_string = input_file.read() # index where the unprocessed part of input_string starts self.current_char_index = 0 # a pair (most recently read token, matched substring of input_string) self.current_token = self.get_token() def skip_white_space(self): '''Consumes all characters in input_string up to the next non-white-space character.''' if (self.current_char_index &gt;= len(self.input_string) - 1): # bad fix for it over-running the end of the file return while self.input_string[self.current_char_index].isspace(): self.current_char_index += 1 return def get_token(self): '''Returns the next token and the part of input_string it matched. Returns None if there is no next token. The characters up to the end of the token are consumed.''' self.skip_white_space() # find the longest prefix of input_string that matches a token token, longest = None, '' for (t, r) in Token.token_regexp: match = re.match(r, self.input_string[self.current_char_index:]) if match and match.end() &gt; len(longest): token, longest = t, match.group() # consume the token by moving the index to the end of the matched part self.current_char_index += len(longest) return (token, longest) def lookahead(self): '''Returns the next token without consuming it. Returns None if there is no next token.''' return self.current_token[0] def consume(self, *tokens): '''Returns the next token and consumes it, if it is in tokens. Raises an exception otherwise. If the token is a number or an identifier, its value is returned.''' if self.current_token[0] not in tokens: print('Token ' + self.current_token[0] + ' isn\'t in the tokens: ') for token in tokens: print(token) raise Exception('Token is not in tokens this shouldn\'t happen much') if self.current_token[0] == 'ID': symbol_table.location(self.current_token[1]) value = self.current_token[1] elif (self.current_token[0] == 'NUM'): value = self.current_token[1] else: value = self.current_token[0] self.current_token = self.get_token() return value class Token: DO = 'DO'; ELSE = 'ELSE'; END = 'END'; IF = 'IF'; THEN = 'THEN'; WHILE = 'WHILE'; SEM = 'SEM'; BEC = 'BEC'; LESS = 'LESS'; EQ = 'EQ'; GRTR = 'GRTR'; LEQ = 'LEQ'; NEQ = 'NEQ'; GEQ = 'GEQ'; ADD = 'ADD'; SUB = 'SUB'; MUL = 'MUL'; DIV = 'DIV'; LPAR = 'LPAR'; RPAR = 'RPAR'; NUM = 'NUM'; ID = 'ID'; READ = 'READ'; WRITE = 'WRITE'; OR = 'OR'; AND = 'AND'; NOT = 'NOT'; # The following list gives the regular expression to match a token. # The order in the list matters for mimicking Flex behaviour. # Longer matches are preferred over shorter ones. # For same-length matches, the first in the list is preferred. token_regexp = [ (DO, 'do'), (ELSE, 'else'), (END, 'end'), (IF, 'if'), (THEN, 'then'), (WHILE, 'while'), (READ, 'read'), (WRITE, 'write'), (OR, 'or'), (AND, 'and'), (NOT, 'not'), (SEM, ';'), (BEC, ':='), (LESS, '&lt;'), (EQ, '='), (NEQ, '!='), (GRTR, '&gt;'), (LEQ, '&lt;='), (GEQ, '&gt;='), (ADD, '[+]'), # + is special in regular expressions (SUB, '-'), (MUL, '[*]'), (DIV, '/'), (LPAR, '[(]'), # ( is special in regular expressions (RPAR, '[)]'), # ) is special in regular expressions (ID, '[a-z]+'), (NUM, '[0-9]+'), ] class Symbol_Table: '''A symbol table maps identifiers to locations.''' def __init__(self): self.symbol_table = {} def size(self): '''Returns the number of entries in the symbol table.''' return len(self.symbol_table) def location(self, identifier): '''Returns the location of an identifier. If the identifier is not in the symbol table, it is entered with a new location. Locations are numbered sequentially starting with 0.''' if identifier in self.symbol_table: return self.symbol_table[identifier] index = len(self.symbol_table) self.symbol_table[identifier] = index return index class Label: def __init__(self): self.current_label = 0 def next(self): '''Returns a new, unique label.''' self.current_label += 1 return 'l' + str(self.current_label) def indent(s, level): return ' '*level + s + '\n' # Each of the following classes is a kind of node in the abstract syntax tree. # indented(level) returns a string that shows the tree levels by indentation. # code() returns a string with JVM bytecode implementing the tree fragment. # true_code/false_code(label) jumps to label if the condition is/is not true. # Execution of the generated code leaves the value of expressions on the stack. class Program_AST: def __init__(self, program): self.program = program def __repr__(self): return repr(self.program) def indented(self, level): return self.program.indented(level) def code(self): program = self.program.code() local = symbol_table.size() java_scanner = symbol_table.location('Java Scanner') return '.class public Program\n' + \ '.super java/lang/Object\n' + \ '.method public &lt;init&gt;()V\n' + \ 'aload_0\n' + \ 'invokenonvirtual java/lang/Object/&lt;init&gt;()V\n' + \ 'return\n' + \ '.end method\n' + \ '.method public static main([Ljava/lang/String;)V\n' + \ '.limit locals ' + str(local) + '\n' + \ '.limit stack 1024\n' + \ 'new java/util/Scanner\n' + \ 'dup\n' + \ 'getstatic java/lang/System.in Ljava/io/InputStream;\n' + \ 'invokespecial java/util/Scanner.&lt;init&gt;(Ljava/io/InputStream;)V\n' + \ 'astore ' + str(java_scanner) + '\n' + \ program + \ 'return\n' + \ '.end method\n' class Statements_AST: def __init__(self, statements): self.statements = statements def __repr__(self): result = repr(self.statements[0]) for st in self.statements[1:]: result += '; ' + repr(st) return result def indented(self, level): result = indent('Statement(s)', level) for st in self.statements: result += st.indented(level+1) return result def code(self): result = '' for st in self.statements: result += st.code() return result class If_AST: def __init__(self, boolean_expression, then): self.boolean_expression = boolean_expression self.then = then def __repr__(self): return 'if ' + repr(self.boolean_expression) + ' then ' + \ repr(self.then) + ' end' def indented(self, level): return indent('If-Then', level) + \ self.boolean_expression.indented(level+1) + \ self.then.indented(level+1) def code(self): l1 = label_generator.next() return self.boolean_expression.code(l1) + \ self.then.code() + \ l1 + ':\n' class If_Else_AST: def __init__(self, boolean_expression, then, _else): self.boolean_expression = boolean_expression; self.then = then; self._else = _else; def __repr__(self): return 'if ' + repr(self.boolean_expression) + ' then ' + \ repr(self.then) + ' else ' + \ repr(self._else) + ' end' def indented(self, level): return indent('If-Then-Else', level) + \ self.boolean_expression.indented(level+1) + \ self.then.indented(level+1) + \ indent('Else', level+1) + \ self._else.indented(level+1) def code(self): l1 = label_generator.next() l2 = label_generator.next() return self.boolean_expression.code(l1) + \ self.then.code() + \ 'goto ' + l2 + '\n' + \ l1 + ':\n' + \ self._else.code() + \ l2 + ':\n' class While_AST: def __init__(self, boolean_term, body): self.boolean_term = boolean_term self.body = body def __repr__(self): return 'while ' + repr(self.boolean_term) + ' do ' + \ repr(self.body) + ' end' def indented(self, level): return indent('While-Do', level) + \ self.boolean_term.indented(level+1) + \ self.body.indented(level+2) def code(self): l1 = label_generator.next() l2 = label_generator.next() return l1 + ':\n' + \ self.boolean_term.code(l2) + \ self.body.code() + \ 'goto ' + l1 + '\n' + \ l2 + ':\n' class Assign_AST: def __init__(self, identifier, expression): self.identifier = identifier self.expression = expression def __repr__(self): return repr(self.identifier) + ':=' + repr(self.expression) def indented(self, level): return indent('Assign', level) + \ self.identifier.indented(level+1) + \ self.expression.indented(level+1) def code(self): loc = symbol_table.location(self.identifier.identifier) return self.expression.code() + \ 'istore ' + str(loc) + '\n' class Write_AST: def __init__(self, expression): self.expression = expression def __repr__(self): return 'write ' + repr(self.expression) def indented(self, level): return indent('Write', level) + self.expression.indented(level+1) def code(self): return 'getstatic java/lang/System/out Ljava/io/PrintStream;\n' + \ self.expression.code() + \ 'invokestatic java/lang/String/valueOf(I)Ljava/lang/String;\n' + \ 'invokevirtual java/io/PrintStream/println(Ljava/lang/String;)V\n' class Read_AST: def __init__(self, identifier): self.identifier = identifier def __repr__(self): return 'read ' + repr(self.identifier) def indented(self, level): return indent('Read', level) + self.identifier.indented(level+1) def code(self): java_scanner = symbol_table.location('Java Scanner') loc = symbol_table.location(self.identifier.identifier) return 'aload ' + str(java_scanner) + '\n' + \ 'invokevirtual java/util/Scanner.nextInt()I\n' + \ 'istore ' + str(loc) + '\n' class Comparison_AST: def __init__(self, left, op, right): self.left = left self.op = op self.right = right def __repr__(self): op = { Token.LESS:'&lt;', Token.EQ:'=', Token.GRTR:'&gt;', Token.LEQ:'&lt;=', Token.NEQ:'!=', Token.GEQ:'&gt;=' } return repr(self.left) + op[self.op] + repr(self.right) def indented(self, level): return indent(self.op, level) + \ self.left.indented(level+1) + \ self.right.indented(level+1) def true_code(self, label): op = { Token.LESS:'if_icmplt', Token.EQ:'if_icmpeq', Token.GRTR:'if_icmpgt', Token.LEQ:'if_icmple', Token.NEQ:'if_icmpne', Token.GEQ:'if_icmpge' } return self.left.code() + \ self.right.code() + \ op[self.op] + ' ' + label + '\n' def false_code(self, label): # Negate each comparison because of jump to "false" label. op = { Token.LESS:'if_icmpge', Token.EQ:'if_icmpne', Token.GRTR:'if_icmple', Token.LEQ:'if_icmpgt', Token.NEQ:'if_icmpeq', Token.GEQ:'if_icmplt' } return self.left.code() + \ self.right.code() + \ op[self.op] + ' ' + label + '\n' class Expression_AST: def __init__(self, left, op, right): self.left = left self.op = op self.right = right def __repr__(self): op = { Token.ADD:'+', Token.SUB:'-', Token.MUL:'*', Token.DIV:'/' } return '(' + repr(self.left) + op[self.op] + repr(self.right) + ')' def indented(self, level): return indent(self.op, level) + \ self.left.indented(level+1) + \ self.right.indented(level+1) def code(self): op = { Token.ADD:'iadd', Token.SUB:'isub', Token.MUL:'imul', Token.DIV:'idiv' } return self.left.code() + \ self.right.code() + \ op[self.op] + '\n' class Number_AST: def __init__(self, number): self.number = number def __repr__(self): return self.number def indented(self, level): return indent(self.number, level) def code(self): # works only for short numbers return 'sipush ' + self.number + '\n' class Identifier_AST: def __init__(self, identifier): self.identifier = identifier def __repr__(self): return self.identifier def indented(self, level): return indent(self.identifier, level) def code(self): loc = symbol_table.location(self.identifier) return 'iload ' + str(loc) + '\n' class BooleanFactor_AST: def __init__(self, condition, logic): self.condition = condition self.logic = logic def __repr__(self): if self.logic == False: return 'NOT ' + repr(self.condition) else: return repr(self.condition) def indented(self, level): if self.logic == False: return indent('NOT ', level) + self.condition.indented(level + 1) else: return self.condition.indented(level) def false_code(self, label): if self.logic == True: return self.condition.false_code(label) else: return self.condition.true_code(label) return def true_code(self, label): if self.logic == True: return self.condition.true_code(label) else: return self.condition.false_code(label) class BooleanTerm_AST: def __init__(self, terms): self.terms = terms def __repr__(self): result = repr(self.terms[0]) for term in self.terms[1:]: result = result + ' AND ' + repr(term) return result def indented(self, level): result = self.terms[0].indented(level) for term in self.terms[1:]: result = result + indent('AND', level) result = result + term.indented(level) return result def code(self, label): result = '' for term in self.terms: result = result + term.false_code(label) return result class BooleanExpression_AST: def __init__(self, expressions): self.expressions = expressions def __repr__(self): result = repr(self.expressions[0]) for expression in self.expressions[1:]: result = result + ' OR ' + repr(expression) return result def indented(self, level): result = self.expressions[0].indented(level) indentation = 0 for expression in self.expressions[1:]: indentation += 1 result = result + indent('OR', level + indentation) result = result + expression.indented(level + indentation) return result def code(self, label): result = '' for expression in self.expressions: result = result + expression.code(label) return result # The following methods comprise the recursive-descent parser. def program(): sts = statements() return Program_AST(sts) def statements(): result = [statement()] while scanner.lookahead() == Token.SEM: scanner.consume(Token.SEM) st = statement() result.append(st) return Statements_AST(result) def statement(): if scanner.lookahead() == Token.IF: return if_statement() elif scanner.lookahead() == Token.WHILE: return while_statement() elif scanner.lookahead() == Token.ID: return assignment() elif scanner.lookahead() == Token.READ: return read(); elif scanner.lookahead() == Token.WRITE: return write(); else: # error return scanner.consume(Token.IF, Token.WHILE, Token.ID) def if_statement(): scanner.consume(Token.IF) condition = boolean_expression() scanner.consume(Token.THEN) then = statements() if scanner.lookahead() == Token.END: scanner.consume(Token.END) return If_AST(condition, then) else: scanner.consume(Token.ELSE) _else = statements() scanner.consume(Token.END) return If_Else_AST(condition, then, _else) def while_statement(): scanner.consume(Token.WHILE) condition = boolean_expression() scanner.consume(Token.DO) body = statements() scanner.consume(Token.END) return While_AST(condition, body) def assignment(): ident = identifier() scanner.consume(Token.BEC) expr = expression() return Assign_AST(ident, expr) def read(): scanner.consume(Token.READ) variable = identifier() return Read_AST(variable) def write(): scanner.consume(Token.WRITE) expr = expression() return Write_AST(expr) def comparison(): left = expression() op = scanner.consume(Token.LESS, Token.EQ, Token.GRTR, Token.LEQ, Token.NEQ, Token.GEQ) right = expression() return Comparison_AST(left, op, right) def expression(): result = term() while scanner.lookahead() in [Token.ADD, Token.SUB]: op = scanner.consume(Token.ADD, Token.SUB) tree = term() result = Expression_AST(result, op, tree) return result def term(): result = factor() while scanner.lookahead() in [Token.MUL, Token.DIV]: op = scanner.consume(Token.MUL, Token.DIV) tree = factor() result = Expression_AST(result, op, tree) return result def factor(): if scanner.lookahead() == Token.LPAR: scanner.consume(Token.LPAR) result = expression() scanner.consume(Token.RPAR) return result elif scanner.lookahead() == Token.NUM: value = scanner.consume(Token.NUM) return Number_AST(value) elif scanner.lookahead() == Token.ID: return identifier() else: # error return scanner.consume(Token.LPAR, Token.NUM, Token.ID) def identifier(): value = scanner.consume(Token.ID) return Identifier_AST(value) def boolean_factor(): if scanner.lookahead() == Token.NOT: scanner.consume(Token.NOT) logic = False else: logic = True result = comparison() return BooleanFactor_AST(result, logic) def boolean_term(): result = [boolean_factor()] while scanner.lookahead() in [Token.AND]: scanner.consume(scanner.lookahead()) temp = boolean_factor() result.append(temp) return BooleanTerm_AST(result) def boolean_expression(): result = [boolean_term()] while scanner.lookahead() in [Token.OR]: scanner.consume(scanner.lookahead()) temp = boolean_term() result.append(temp) return BooleanExpression_AST(result) # Initialise scanner, symbol table and label generator. #scanner = Scanner(open('test.txt')) scanner = Scanner(sys.stdin) symbol_table = Symbol_Table() symbol_table.location('Java Scanner') # fix a location for the Java Scanner label_generator = Label() # Uncomment the following to test the scanner without the parser. # This shows a list of all tokens in the input. # #token = scanner.lookahead() #while token != None: # print(token) # scanner.consume(token) # token = scanner.lookahead() #exit() # Call the parser. ast = program() assert scanner.lookahead() == None # Uncomment the following to test the parser without the code generator. # The first line gives back the program by calling __repr__ of the AST classes. # The second line shows the syntax tree with levels indicated by indentation. # #print(ast) #print(ast.indented(0)) #exit() # Call the code generator. # This translates the abstract syntax tree to JVM bytecode. # It can be assembled to a class file by Jasmin: http://jasmin.sourceforge.net/ print(ast.code()) </code></pre> <p>testing bat file</p> <pre><code>python compiler.py &lt;test.txt&gt; Program.j java -Xmx100m -jar jasmin.jar Program.j java -Xmx100m Program &lt; testInput.txt &gt; test_output.txt </code></pre> <p>and language (BNF)</p> <pre><code>Program = Statements Statements = Statement (; Statement) Statement = If | While | Assignment If = if Comparison then Statements end While = while Comparison do Statements end Assignment = identifier := Expression Comparison = Expression Relation Expression Relation = = | != | &lt; | &lt;= | &gt; | &gt;= Expression = Term ((+ | -) Term) Term = Factor ((* | /) Factor) Factor = (Expression) | number | identifier BooleanExpression = BooleanTerm (or BooleanTerm)* BooleanTerm = BooleanFactor (and BooleanFactor)* BooleanFactor = not BooleanFactor | Comparison </code></pre> <p>I think thats all that is relevant, cheers if you take a go at helping me on this</p>
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    1. USSeki
    1. USZeno15
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      1. POPython compiler for simple language to java vm code algorithm
      1. USNicola Musatti
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      1. This table or related slice is empty.
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      1. VTUpMod
    1. COeep, the j's in the language description are meant to be bitwise or's (|)
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      1. USZeno15
    2. COYou can edit your question (click the gray `edit` button at the bottom of the post) if you want to fix that.
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      1. POPython compiler for simple language to java vm code algorithm
      1. USWesley Baugh
    3. COcheers for that
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      1. USZeno15
 

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