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This lecture was delivered by Ruiz Pereira at Chandra Shekhar Azad University of Agriculture
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void Foo() { int a, b, max; read a; read b; if (a > b) max = a; else max = b; write max; }
COMPILER Taste
CHARACTERS letter = 'A'..'Z' + 'a'..'z'. digit = '0'..'9'.
TOKENS ident = letter {letter | digit}. number = digit {digit}.
COMMENTS FROM "/" TO "/" NESTED COMMENTS FROM "//" TO '\r' '\n'
IGNORE '\r' + '\n' + '\t'
PRODUCTIONS ... END Taste.
public class CodeGenerator { public int pc ; public int progStart ; public CodeGenerator () {...} public void Emit (int op) {...} public void Emit (int op, int val) {...} public void Patch (int adr, int val) {...} ... }
Taste (. string name; .) = "program" Ident
VarDecl (. string name; int type; .) = Type
ProcDecl (. string name; Obj obj; int adr; .) = "void" Ident
Type
public SymbolTable tab; public CodeGenerator gen;
Factor
| number (. n = Convert.ToInt32(t.val); gen.Emit(CONST, n); type = INT; .)
| '-' Factor
| "true" (. gen.Emit(CONST, 1); type = BOOL; .) | "false" (. gen.Emit(CONST, 0); type = BOOL; .) ).
Ident
Stat (. int type; string name; Obj obj; int adr, adr2, loopstart; .) = Ident
| "read" Ident
| "write" Expr
| '{' { Stat | VarDecl } '}'
using System;
public class Taste {
public static void Main (string[] arg) { if (arg.Length > 0) { Scanner scanner = new Scanner(arg[0]); Parser parser = new Parser(scanner); parser.tab = new SymbolTable(parser); parser.gen = new CodeGenerator(); parser.Parse(); if (parser.errors.count == 0) parser.gen.Interpret("Taste.IN"); } else Console.WriteLine("-- No source file specified"); }
c:> coco Taste.atg c:> csc Taste.cs Scanner.cs Parser.cs SymbolTable.cs CodeGenerator.cs c:> Taste Sample.tas
