MH_Parser.java

// File:   MH_Parser.java

// Java template file for parser component of Informatics 2A Assignment 1.
// Students should add a method body for the LL(1) parse table for Micro-Haskell.


import java.io.* ;
 
class MH_Parser extends GenParser implements PARSER {

    String startSymbol() {return "#Prog" ;}

    // Right hand sides of all productions in grammar:

    static String[] epsilon              = new String[] { } ;
    static String[] Decl_Prog            = new String[] {"#Decl", "#Prog"} ;
    static String[] TypeDecl_TermDecl    = new String[] {"#TypeDecl", "#TermDecl"} ;
    static String[] VAR_has_Type         = new String[] {"VAR", "::", "#Type", ";"} ;
    static String[] Type0_TypeRest       = new String[] {"#Type0", "#TypeRest"} ;
    static String[] arrow_Type           = new String[] {"->", "#Type"} ;
    static String[] Integer              = new String[] {"Integer"} ;
    static String[] Bool                 = new String[] {"Bool"} ;
    static String[] lbr_Type_rbr         = new String[] {"(", "#Type", ")"} ;
    static String[] VAR_Args_eq_Exp      = new String[] {"VAR", "#Args", "=", "#Exp", ";"} ;
    static String[] VAR_Args             = new String[] {"VAR", "#Args"} ;
    static String[] Exp0                 = new String[] {"#Exp0"} ;
    static String[] if_then_else         = new String[] {"if", "#Exp", "then", "#Exp", "else", "#Exp"} ;
    static String[] Exp1_Rest0           = new String[] {"#Exp1", "#Rest0"} ;
    static String[] eqeq_Exp1            = new String[] {"==", "#Exp1"} ;
    static String[] lteq_Exp1            = new String[] {"<=", "#Exp1"} ;
    static String[] Exp2_Rest1           = new String[] {"#Exp2", "#Rest1"} ;
    static String[] plus_Exp2_Rest1      = new String[] {"+", "#Exp2", "#Rest1"} ;
    static String[] minus_Exp2_Rest1     = new String[] {"-", "#Exp2", "#Rest1"} ;
    static String[] Exp3_Rest2           = new String[] {"#Exp3", "#Rest2"} ;
    static String[] VAR                  = new String[] {"VAR"} ;
    static String[] NUM                  = new String[] {"NUM"} ;
    static String[] BOOLEAN              = new String[] {"BOOLEAN"} ;
    static String[] lbr_Exp_rbr          = new String[] {"(", "#Exp", ")"} ;

    // may add auxiliary methods here if desired
    // LIST OF NONTERMINALS
        // Prog
        // Decl
        // TypeDecl
        // Type
        // TypeRest
        // Type0
        // TermDecl
        // Args
        // Exp
        // Exp0
        // Rest0
        // Exp1
        // Rest1
        // Exp2
        // Rest2
        // Exp3

    String[] tableEntry (String nonterm, String tokClass) {
        // add main code here
        if (nonterm.equals("#Prog")) {
            if (tokClass == null) {
                return epsilon;
            } else if (tokClass.equals("VAR")) {
                return Decl_Prog;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#Decl")) {
            if (tokClass.equals("VAR")) {
                return TypeDecl_TermDecl;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#TypeDecl")) {
            if (tokClass.equals("VAR")) {
                return VAR_has_Type;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#Type")) {
            if (tokClass.equals("Integer")) {
                return Type0_TypeRest;
            } else if (tokClass.equals("Bool")) {
                return Type0_TypeRest;
            } else if (tokClass.equals("(")) {
                return Type0_TypeRest;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#TypeRest")) {
            if (tokClass.equals(";")) {
                return epsilon;
            } else if (tokClass.equals(")")) {
                return epsilon;
            } else if (tokClass.equals("->")) {
                return arrow_Type;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#Type0")) {
            if (tokClass.equals("Integer")) {
                return Integer;
            } else if (tokClass.equals("Bool")) {
                return Bool;
            } else if (tokClass.equals("(")) {
                return lbr_Type_rbr;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#TermDecl")) {
            if (tokClass.equals("VAR")) {
                return VAR_Args_eq_Exp;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#Args")) {
            if (tokClass.equals("VAR")) {
                return VAR_Args;
            } else if (tokClass.equals("=")) {
                return epsilon;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#Exp")) {
            if (tokClass.equals("VAR")) {
                return Exp0;
            } else if (tokClass.equals("if")) {
                return if_then_else;
            } else if (tokClass.equals("NUM")) {
                return Exp0;
            } else if (tokClass.equals("BOOLEAN")) {
                return Exp0;
            } else if (tokClass.equals("(")) {
                return Exp0;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#Exp0")) {
            if (tokClass.equals("VAR")) {
                return Exp1_Rest0;
            } else if (tokClass.equals("NUM")) {
                return Exp1_Rest0;
            } else if (tokClass.equals("BOOLEAN")) {
                return Exp1_Rest0;
            } else if (tokClass.equals("(")) {
                return Exp1_Rest0;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#Rest0")) {
            if (tokClass.equals(";")) {
                return epsilon;
            } else if (tokClass.equals("then")) {
                return epsilon;
            } else if (tokClass.equals("else")) {
                return epsilon;
            } else if (tokClass.equals("==")) {
                return eqeq_Exp1;
            } else if (tokClass.equals("<=")) {
                return lteq_Exp1;
            } else if (tokClass.equals(")")) {
                return epsilon;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#Exp1")) {
            if (tokClass.equals("VAR")) {
                return Exp2_Rest1;
            } else if (tokClass.equals("NUM")) {
                return Exp2_Rest1;
            } else if (tokClass.equals("BOOLEAN")) {
                return Exp2_Rest1;
            } else if (tokClass.equals("(")) {
                return Exp2_Rest1;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#Rest1")) {
            if (tokClass.equals(";")) {
                return epsilon;
            } else if (tokClass.equals("then")) {
                return epsilon;
            } else if (tokClass.equals("else")) {
                return epsilon;
            } else if (tokClass.equals("==")) {
                return epsilon;
            } else if (tokClass.equals("<=")) {
                return epsilon;
            } else if (tokClass.equals("+")) {
                return plus_Exp2_Rest1;
            } else if (tokClass.equals("-")) {
                return minus_Exp2_Rest1;
            } else if (tokClass.equals(")")) {
                return epsilon;
            } else {
                return null;
            }
        }
        
        if (nonterm.equals("#Exp2")) {
            if (tokClass.equals("VAR")) {
                return Exp3_Rest2;
            } else if (tokClass.equals("NUM")) {
                return Exp3_Rest2;
            } else if (tokClass.equals("BOOLEAN")) {
                return Exp3_Rest2;
            } else if (tokClass.equals("(")) {
                return Exp3_Rest2;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#Rest2")) {
            if (tokClass.equals("VAR")) {
                return Exp3_Rest2;
            } else if (tokClass.equals(";")) {
                return epsilon;
            } else if (tokClass.equals("then")) {
                return epsilon;
            } else if (tokClass.equals("else")) {
                return epsilon;
            } else if (tokClass.equals("==")) {
                return epsilon;
            } else if (tokClass.equals("<=")) {
                return epsilon;
            } else if (tokClass.equals("+")) {
                return epsilon;
            } else if (tokClass.equals("-")) {
                return epsilon;
            } else if (tokClass.equals("NUM")) {
                return Exp3_Rest2;
            } else if (tokClass.equals("BOOLEAN")) {
                return Exp3_Rest2;
            } else if (tokClass.equals("(")) {
                return Exp3_Rest2;
            } else if (tokClass.equals(")")) {
                return epsilon;
            } else {
                return null;
            }
        }

        if (nonterm.equals("#Exp3")) {
            if (tokClass.equals("VAR")) {
                return VAR;
            } else if (tokClass.equals("NUM")) {
                return NUM;
            } else if (tokClass.equals("BOOLEAN")) {
                return BOOLEAN;
            } else if (tokClass.equals("(")) {
                return lbr_Exp_rbr;
            } else {
                return null;
            }
        }

        else {
            return null;
        }

    }
}


// For testing

class MH_ParserDemo {

    static PARSER MH_Parser = new MH_Parser() ;

    public static void main (String[] args) throws Exception {
    Reader reader = new BufferedReader (new FileReader (args[0])) ;
    LEX_TOKEN_STREAM MH_Lexer = 
        new CheckedSymbolLexer (new MH_Lexer (reader)) ;
    TREE theTree = MH_Parser.parseTokenStream (MH_Lexer) ;
    }
}