assign4.lex

%{

/*-------------------------------------------------------------------------*
 *---																																		---*
 *---		assign4.lex																											---*
 *---																																		---*
 *---	    This file defines the LEX-style tokenizer for the language		---*
 *---	at the bottom of page 173 of Fischer, Cytron, LeBlanc "Crafting		---*
 *---	 a Compiler" Addison-Wesley, 2010.																---*
 *---																																		---*
 *---		----		----		----		----		----		----		----		----		---*
 *---																																		---*
 *---	Version 1.0		2016 May 25		Joseph Phillips												---*
 *---																																		---*
 *-------------------------------------------------------------------------*/

#include	"assign4.h"
#include	"assign4.tab.h"

#undef YY_INPUT
#define YY_INPUT(buffer, result, maxSize)  { result = ourInput(buffer,maxSize); }

extern int ourInput(char* buffer, int maxSize);

%}

%%

[0-9]+ {
	printf("%s", yytext);
	yylval.number_=atoi(yytext);
	return(NUM);
}

[ \t\n] { /* ignore spaces */; }

\( { return(LPAREN); }
\) { return(RPAREN); }
\+ { return(PLUS); }
\* { return(STAR); }



%%

//  PURPOSE:  To hold the input file from which to read the program (if it is
//	not 'stdin').
FILE*	filePtr	= NULL;

//  PURPOSE:  To point to the beginning of the input yet to read (if being
//	typed from the command line).
char*	textPtr	= NULL;

//  PURPOSE:  To point to the end of all input (if being typed from the command
//	line).
char*	textEndPtr = NULL;

//  PURPOSE:  To hold the value that results from parse.
double result = 0.0;

//  PURPOSE:  To return 1 if the tokenizer should quit after EOF is reached.
//	Returns 0 otherwise.  No parameters.
int	yywrap(){
	return(1);
}

//  PURPOSE:  To show the error message pointed to by 'cPtr'.  Returns '0'.
int	yyerror	(const char *cPtr)
{
  printf("%s, sorry!\n",cPtr);
  return(1);
}

//  PURPOSE:  To get up to 'maxSize' more characters of input and put them
//	into 'buffer'.   Returns how many characters were obtained.
int ourInput(	char* buffer, int maxSize ) {
  unsigned int n;

  if (filePtr == NULL) {
    n	= MIN(maxSize, textEndPtr - textPtr);

    if (n > 0) {
      memcpy(buffer,textPtr,n);
      textPtr	+= n;
    }
  } else {
    errno	= 0;

    while  ( (n = fread(buffer,1,maxSize,yyin)) == 0 && ferror(yyin))
    {
      if (errno != EINTR) {
        fprintf(stderr,"Reading file failed: %s\n",strerror(errno));
				exit(EXIT_FAILURE);
      }

      errno	= 0;
      clearerr(yyin);
    }
  }

  return(n);
}

//  PURPOSE:  To parse and execute the program whose filename is given on the
//	command line at 'argv[1]' (if 'argc' >= 1), or that the user types in.
//	Returns 'EXIT_SUCCESS' on success or 'EXIT_FAILURE' otherwise.
int main (int argc, char* argv[]) {
  //  I.  Application validity check:

  //  II.  Parse and execute program:
  //  II.A.  Get program source:
  char line[LINE_LEN];

  if ( (argc >= 2)  &&  ( (filePtr = fopen(argv[1],"r")) != NULL ) )
  {
    yyin	= filePtr;
  } else {
    printf("Please enter an expression: ");
    textPtr	= fgets(line,LINE_LEN,stdin);
    textEndPtr	= textPtr + strlen(textPtr);
  }

  //  II.B.  Attempt to parse program:
  try {
    yyparse();
  }
  catch  (std::string*	errStrPtr)
  {
    fprintf(stderr,"Error: %s.\n",errStrPtr->c_str());
    delete(errStrPtr);
  }

  //  II.C.  Print output:
  printf("%g\n",result);

  //  II.D. Clean up:
  //  II.D.1.  Close file (if open):
  if  (filePtr != NULL)
    fclose(filePtr);

  fflush(stdout);

  //  III.  Finished:
  return(EXIT_SUCCESS);
}

assign4.y

%{

/*-------------------------------------------------------------------------*
 *---									                                                  ---*
 *---		assign4.y						                                            ---*
 *---								                                                   	---*
 *---	    This file defines the YACC-style grammar for the language	    ---*
 *---	at the bottom of page 173 of Fischer, Cytron, LeBlanc "Crafting	  ---*
 *---	 a Compiler" Addison-Wesley, 2010.			                         	---*
 *---									                                                  ---*
 *---	  ----	 ----	   ----	   ----	  ----	   ----	   ----	  ----	    ---*
 *---									                                                  ---*
 *---	Version 1.0		2016 May 25		Joseph Phillips	                      ---*
 *---									                                                  ---*
 *-------------------------------------------------------------------------*/

#include "assign4.h"

%}

%union
{
  double number_;
  NumberList* listPtr_;
}

%start			start
%nonassoc		LPAREN RPAREN
%nonassoc		STAR PLUS
%token	<number_>	NUM
%type	<number_>	start
%type	<number_>	expr
%type	<number_>	value
%type	<listPtr_>	values

%%

//  YOUR CODE HERE FOR GRAMMAR RULES
start : value
        {
          printf("start : value\n");
        };

value : NUM
        {
          printf("value : NUM\n");
        }
      | LPAREN expr RPAREN
        {
          printf("value : LPAREN expr RPAREN\n");
        };

expr  : PLUS value value
        {
          printf("expr : PLUS value value\n");
        }
      | STAR values
        {
          printf("expr : STAR values\n");
        }

values  : value value
          {
            printf("values : value value\n");
          }
        |
          {
            printf("values : \n");
          }