src/bdd/parse/parseCore.c

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/*
        Some aspects of Boolean Formula Parser:

 1) The names in the boolean formulas can be any strings of symbols
    that start with char or underscore and contain chars, digits 
    and underscores: For example: 1) a&b <+> c'&d => a + b;   
    2) a1 b2 c3' dummy' + (a2+b2')c3 dummy
 2) Constant values 0 and 1 can be used just like normal variables
 3) Any boolean operator (listed below) and parantheses can be used
    any number of times provided there are equal number of opening
    and closing parantheses.
 4) By default, absence of an operator between vars and before and 
    after parantheses is taken for AND. 
 5) Both complementation prefix and complementation suffix can be 
    used at the same time (but who needs this?)
 6) Spaces (tabs, end-of-lines) may be inserted anywhere,
    except between characters of the operations: <=>, =>, <=, <+>
 7) The stack size is defined by macro STACKSIZE and is used by the 
    stack constructor.
*/
 

#include "parseInt.h"

// the list of operation symbols to be used in expressions
#define PARSE_SYM_OPEN    '('   // opening paranthesis
#define PARSE_SYM_CLOSE   ')'   // closing paranthesis
#define PARSE_SYM_LOWER   '['   // shifts one rank down 
#define PARSE_SYM_RAISE   ']'   // shifts one rank up
#define PARSE_SYM_CONST0  '0'   // constant 0
#define PARSE_SYM_CONST1  '1'   // constant 1
#define PARSE_SYM_NEGBEF1 '!'   // negation before the variable
#define PARSE_SYM_NEGBEF2 '~'   // negation before the variable
#define PARSE_SYM_NEGAFT  '\''  // negation after the variable
#define PARSE_SYM_AND1    '&'   // logic AND
#define PARSE_SYM_AND2    '*'   // logic AND
#define PARSE_SYM_XOR1    '<'   // logic EXOR   (the 1st symbol) 
#define PARSE_SYM_XOR2    '+'   // logic EXOR   (the 2nd symbol)
#define PARSE_SYM_XOR3    '>'   // logic EXOR   (the 3rd symbol)
#define PARSE_SYM_OR      '+'   // logic OR
#define PARSE_SYM_EQU1    '<'   // equvalence   (the 1st symbol)
#define PARSE_SYM_EQU2    '='   // equvalence   (the 2nd symbol)
#define PARSE_SYM_EQU3    '>'   // equvalence   (the 3rd symbol)
#define PARSE_SYM_FLR1    '='   // implication  (the 1st symbol)
#define PARSE_SYM_FLR2    '>'   // implication  (the 2nd symbol)
#define PARSE_SYM_FLL1    '<'   // backward imp (the 1st symbol)
#define PARSE_SYM_FLL2    '='   // backward imp (the 2nd symbol)
// PARSE_SYM_FLR1 and PARSE_SYM_FLR2 should be the same as PARSE_SYM_EQU2 and PARSE_SYM_EQU3!

// the list of opcodes (also specifying operation precedence)
#define PARSE_OPER_NEG 10  // negation
#define PARSE_OPER_AND  9  // logic AND
#define PARSE_OPER_XOR  8  // logic EXOR   (a'b | ab')   
#define PARSE_OPER_OR   7  // logic OR
#define PARSE_OPER_EQU  6  // equvalence   (a'b'| ab )
#define PARSE_OPER_FLR  5  // implication  ( a' | b )
#define PARSE_OPER_FLL  4  // backward imp ( 'b | a )
#define PARSE_OPER_MARK 1  // OpStack token standing for an opening paranthesis

// these are values of the internal Flag
#define PARSE_FLAG_START  1 // after the opening parenthesis 
#define PARSE_FLAG_VAR    2 // after operation is received
#define PARSE_FLAG_OPER   3 // after operation symbol is received
#define PARSE_FLAG_ERROR  4 // when error is detected

#define STACKSIZE 1000

static DdNode * Parse_ParserPerformTopOp( DdManager * dd, Parse_StackFn_t * pStackFn, int Oper );


DdNode * Parse_FormulaParser( FILE * pOutput, char * pFormulaInit, int nVars, int nRanks, 
      char * ppVarNames[], DdManager * dd, DdNode * pbVars[] )
{
    char * pFormula;
    Parse_StackFn_t * pStackFn;
    Parse_StackOp_t * pStackOp;
    DdNode * bFunc, * bTemp;
    char * pTemp;
    int nParans, fFound, Flag;
        int Oper, Oper1, Oper2;
    int i, v, fLower;

    // make sure that the number of vars and ranks is correct
    if ( nVars * (nRanks + 1) > dd->size )
    {
        printf( "Parse_FormulaParser(): The BDD manager does not have enough variables.\n" );
        return NULL;
    }

    // make sure that the number of opening and closing parantheses is the same
    nParans = 0;
    for ( pTemp = pFormulaInit; *pTemp; pTemp++ )
        if ( *pTemp == '(' )
            nParans++;
        else if ( *pTemp == ')' )
            nParans--;
    if ( nParans != 0 )
    {
        fprintf( pOutput, "Parse_FormulaParser(): Different number of opening and closing parantheses ().\n" );
        return NULL;
    }

    nParans = 0;
    for ( pTemp = pFormulaInit; *pTemp; pTemp++ )
        if ( *pTemp == '[' )
            nParans++;
        else if ( *pTemp == ']' )
            nParans--;
    if ( nParans != 0 )
    {
        fprintf( pOutput, "Parse_FormulaParser(): Different number of opening and closing brackets [].\n" );
        return NULL;
    }

    // copy the formula
    pFormula = ALLOC( char, strlen(pFormulaInit) + 3 );
    sprintf( pFormula, "(%s)", pFormulaInit );

    // start the stacks
    pStackFn = Parse_StackFnStart( STACKSIZE );
    pStackOp = Parse_StackOpStart( STACKSIZE );

    Flag = PARSE_FLAG_START;
    fLower = 0;
    for ( pTemp = pFormula; *pTemp; pTemp++ )
        {
                switch ( *pTemp )
            {
                // skip all spaces, tabs, and end-of-lines
        case ' ':
        case '\t':
        case '\r':
        case '\n':
                        continue;

                // treat Constant 0 as a variable
                case PARSE_SYM_CONST0:
                    Parse_StackFnPush( pStackFn, b0 );   Cudd_Ref( b0 );
                        if ( Flag == PARSE_FLAG_VAR )
                        {
                                fprintf( pOutput, "Parse_FormulaParser(): No operation symbol before constant 0.\n" );
                                Flag = PARSE_FLAG_ERROR; 
                break;
                        }
            Flag = PARSE_FLAG_VAR; 
            break;

                // the same for Constant 1
                case PARSE_SYM_CONST1:
                    Parse_StackFnPush( pStackFn, b1 );    Cudd_Ref( b1 );
                        if ( Flag == PARSE_FLAG_VAR )
                        {
                                fprintf( pOutput, "Parse_FormulaParser(): No operation symbol before constant 1.\n" );
                                Flag = PARSE_FLAG_ERROR; 
                break;
                        }
            Flag = PARSE_FLAG_VAR; 
            break;

                case PARSE_SYM_NEGBEF1:
                case PARSE_SYM_NEGBEF2:
                        if ( Flag == PARSE_FLAG_VAR )
                        {// if NEGBEF follows a variable, AND is assumed
                                Parse_StackOpPush( pStackOp, PARSE_OPER_AND );
                                Flag = PARSE_FLAG_OPER;
                        }
                Parse_StackOpPush( pStackOp, PARSE_OPER_NEG );
                        break;

                case PARSE_SYM_NEGAFT:
                        if ( Flag != PARSE_FLAG_VAR )
                        {// if there is no variable before NEGAFT, it is an error
                                fprintf( pOutput, "Parse_FormulaParser(): No variable is specified before the negation suffix.\n" );
                                Flag = PARSE_FLAG_ERROR; 
                break;
                        }
                        else // if ( Flag == PARSE_FLAG_VAR )
                                Parse_StackFnPush( pStackFn, Cudd_Not( Parse_StackFnPop(pStackFn) ) );
                        break;

        case PARSE_SYM_AND1:
        case PARSE_SYM_AND2:
        case PARSE_SYM_OR:
                        if ( Flag != PARSE_FLAG_VAR )
                        {
                                fprintf( pOutput, "Parse_FormulaParser(): There is no variable before AND, EXOR, or OR.\n" );
                                Flag = PARSE_FLAG_ERROR; 
                break;
                        }
                        if ( *pTemp == PARSE_SYM_AND1 || *pTemp == PARSE_SYM_AND2 )
                                Parse_StackOpPush( pStackOp, PARSE_OPER_AND );
                        else //if ( Str[Pos] == PARSE_SYM_OR )
                                Parse_StackOpPush( pStackOp, PARSE_OPER_OR );
                        Flag = PARSE_FLAG_OPER; 
            break;

                case PARSE_SYM_EQU1:
                        if ( Flag != PARSE_FLAG_VAR )
                        { 
                                fprintf( pOutput, "Parse_FormulaParser(): There is no variable before Equivalence or Implication\n" );
                                Flag = PARSE_FLAG_ERROR; break;
                        }
                        if ( pTemp[1] == PARSE_SYM_EQU2 )
                        { // check what is the next symbol in the string
                pTemp++; 
                                if ( pTemp[1] == PARSE_SYM_EQU3 )
                            {   
                    pTemp++; 
                    Parse_StackOpPush( pStackOp, PARSE_OPER_EQU ); 
                }
                            else
                            {   
                    Parse_StackOpPush( pStackOp, PARSE_OPER_FLL ); 
                }
                        }
                        else if ( pTemp[1] == PARSE_SYM_XOR2 )
            {
                pTemp++; 
                                if ( pTemp[1] == PARSE_SYM_XOR3 )
                            {   
                    pTemp++; 
                    Parse_StackOpPush( pStackOp, PARSE_OPER_XOR ); 
                }
                            else
                            {   
                                    fprintf( pOutput, "Parse_FormulaParser(): Wrong symbol after \"%c%c\"\n", PARSE_SYM_EQU1, PARSE_SYM_XOR2 );
                                    Flag = PARSE_FLAG_ERROR; 
                    break;
                }
            }
                        else
                        {
                                fprintf( pOutput, "Parse_FormulaParser(): Wrong symbol after \"%c\"\n", PARSE_SYM_EQU1 );
                                Flag = PARSE_FLAG_ERROR; 
                break;
                        }
                        Flag = PARSE_FLAG_OPER; 
            break;

                case PARSE_SYM_EQU2:
                        if ( Flag != PARSE_FLAG_VAR )
                        {
                                fprintf( pOutput, "Parse_FormulaParser(): There is no variable before Reverse Implication\n" );
                                Flag = PARSE_FLAG_ERROR; 
                break;
                        }
                        if ( pTemp[1] == PARSE_SYM_EQU3 )
            {   
                pTemp++; 
                Parse_StackOpPush( pStackOp, PARSE_OPER_FLR ); 
            }
                        else
                        {
                                fprintf( pOutput, "Parse_FormulaParser(): Wrong symbol after \"%c\"\n", PARSE_SYM_EQU2 );
                                Flag = PARSE_FLAG_ERROR; 
                break;
                        }
                        Flag = PARSE_FLAG_OPER; 
            break;

        case PARSE_SYM_LOWER:
                case PARSE_SYM_OPEN:
                        if ( Flag == PARSE_FLAG_VAR )
                                Parse_StackOpPush( pStackOp, PARSE_OPER_AND );
                        Parse_StackOpPush( pStackOp, PARSE_OPER_MARK );
                        // after an opening bracket, it feels like starting over again
                        Flag = PARSE_FLAG_START; 
            break;

        case PARSE_SYM_RAISE:
            fLower = 1;
                case PARSE_SYM_CLOSE:
                        if ( !Parse_StackOpIsEmpty( pStackOp ) )
            {
                                while ( 1 )
                            {
                                    if ( Parse_StackOpIsEmpty( pStackOp ) )
                                        {
                                                fprintf( pOutput, "Parse_FormulaParser(): There is no opening paranthesis\n" );
                                                Flag = PARSE_FLAG_ERROR; 
                        break;
                                        }
                                        Oper = Parse_StackOpPop( pStackOp );
                                        if ( Oper == PARSE_OPER_MARK )
                                                break;

                    // perform the given operation
                    if ( Parse_ParserPerformTopOp( dd, pStackFn, Oper ) == NULL )
                        {
                                fprintf( pOutput, "Parse_FormulaParser(): Unknown operation\n" );
                        free( pFormula );
                                return NULL;
                        }
                            }

                if ( fLower )
                {
                    bFunc = Parse_StackFnPop( pStackFn );
                    bFunc = Extra_bddMove( dd, bTemp = bFunc, -nVars );   Cudd_Ref( bFunc );
                    Cudd_RecursiveDeref( dd, bTemp );
                                        Parse_StackFnPush( pStackFn, bFunc );
                }
            }
                    else
                        {
                                fprintf( pOutput, "Parse_FormulaParser(): There is no opening paranthesis\n" );
                                Flag = PARSE_FLAG_ERROR; 
                break;
                        }
                        if ( Flag != PARSE_FLAG_ERROR )
                            Flag = PARSE_FLAG_VAR; 
            fLower = 0;
                        break;


                default:
            // scan the next name
            fFound = 0;
            for ( i = 0; pTemp[i] && pTemp[i] != ' ' && pTemp[i] != '\t' && pTemp[i] != '\r' && pTemp[i] != '\n'; i++ )
            {
                for ( v = 0; v < nVars; v++ )
                    if ( strncmp( pTemp, ppVarNames[v], i+1 ) == 0 && strlen(ppVarNames[v]) == (unsigned)(i+1) )
                    {
                        pTemp += i;
                        fFound = 1;
                        break;
                    }
                if ( fFound )
                    break;
            }
            if ( !fFound )
                        { 
                                fprintf( pOutput, "Parse_FormulaParser(): The parser cannot find var \"%s\" in the input var list.\n", pTemp ); 
                                Flag = PARSE_FLAG_ERROR; 
                break; 
                        }

                        // assume operation AND, if vars follow one another
                        if ( Flag == PARSE_FLAG_VAR )
                                Parse_StackOpPush( pStackOp, PARSE_OPER_AND );
                        Parse_StackFnPush( pStackFn, pbVars[v] );  Cudd_Ref( pbVars[v] );
            Flag = PARSE_FLAG_VAR; 
            break;
            }

                if ( Flag == PARSE_FLAG_ERROR )
                        break;      // error exit
                else if ( Flag == PARSE_FLAG_START )
                        continue;  //  go on parsing
                else if ( Flag == PARSE_FLAG_VAR )
                        while ( 1 )
                        {  // check if there are negations in the OpStack     
                                if ( Parse_StackOpIsEmpty(pStackOp) )
                                        break;
                Oper = Parse_StackOpPop( pStackOp );
                                if ( Oper != PARSE_OPER_NEG )
                {
                                        Parse_StackOpPush( pStackOp, Oper );
                                        break;
                }
                                else
                                {
                                Parse_StackFnPush( pStackFn, Cudd_Not(Parse_StackFnPop(pStackFn)) );
                                }
                        }
                else // if ( Flag == PARSE_FLAG_OPER )
                        while ( 1 )
                        {  // execute all the operations in the OpStack
                           // with precedence higher or equal than the last one
                                Oper1 = Parse_StackOpPop( pStackOp ); // the last operation
                                if ( Parse_StackOpIsEmpty(pStackOp) ) 
                                {  // if it is the only operation, push it back
                                        Parse_StackOpPush( pStackOp, Oper1 );
                                        break;
                                }
                                Oper2 = Parse_StackOpPop( pStackOp ); // the operation before the last one
                                if ( Oper2 >= Oper1 )  
                                {  // if Oper2 precedence is higher or equal, execute it
//                                      Parse_StackPush( pStackFn,  Operation( FunStack.Pop(), FunStack.Pop(), Oper2 ) );
                    if ( Parse_ParserPerformTopOp( dd, pStackFn, Oper2 ) == NULL )
                        {
                                fprintf( pOutput, "Parse_FormulaParser(): Unknown operation\n" );
                        free( pFormula );
                                return NULL;
                        }
                                        Parse_StackOpPush( pStackOp,  Oper1 );     // push the last operation back
                                }
                                else
                                {  // if Oper2 precedence is lower, push them back and done
                                        Parse_StackOpPush( pStackOp, Oper2 );
                                        Parse_StackOpPush( pStackOp, Oper1 );
                                        break;
                                }
                        }
    }

        if ( Flag != PARSE_FLAG_ERROR )
    {
                if ( !Parse_StackFnIsEmpty(pStackFn) )
            {   
                        bFunc = Parse_StackFnPop(pStackFn);
                        if ( Parse_StackFnIsEmpty(pStackFn) )
                                if ( Parse_StackOpIsEmpty(pStackOp) )
                {
                    Parse_StackFnFree(pStackFn);
                    Parse_StackOpFree(pStackOp);
                    Cudd_Deref( bFunc );
                    free( pFormula );
                                        return bFunc;
                }
                                else
                                        fprintf( pOutput, "Parse_FormulaParser(): Something is left in the operation stack\n" );
                        else
                                fprintf( pOutput, "Parse_FormulaParser(): Something is left in the function stack\n" );
            }
            else
                        fprintf( pOutput, "Parse_FormulaParser(): The input string is empty\n" );
    }
    free( pFormula );
        return NULL;
}

DdNode * Parse_ParserPerformTopOp( DdManager * dd, Parse_StackFn_t * pStackFn, int Oper )
{
    DdNode * bArg1, * bArg2, * bFunc;
    // perform the given operation
    bArg2 = Parse_StackFnPop( pStackFn );
    bArg1 = Parse_StackFnPop( pStackFn );
        if ( Oper == PARSE_OPER_AND )
                bFunc = Cudd_bddAnd( dd, bArg1, bArg2 );
        else if ( Oper == PARSE_OPER_XOR )
                bFunc = Cudd_bddXor( dd, bArg1, bArg2 );
        else if ( Oper == PARSE_OPER_OR )
                bFunc = Cudd_bddOr( dd, bArg1, bArg2 );
        else if ( Oper == PARSE_OPER_EQU )
                bFunc = Cudd_bddXnor( dd, bArg1, bArg2 );
        else if ( Oper == PARSE_OPER_FLR )
                bFunc = Cudd_bddOr( dd, Cudd_Not(bArg1), bArg2 );
        else if ( Oper == PARSE_OPER_FLL )
                bFunc = Cudd_bddOr( dd, Cudd_Not(bArg2), bArg1 );
        else
                return NULL;
    Cudd_Ref( bFunc );
    Cudd_RecursiveDeref( dd, bArg1 );
    Cudd_RecursiveDeref( dd, bArg2 );
        Parse_StackFnPush( pStackFn,  bFunc );
    return bFunc;
}

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