/* Infix notation calculator--calc */

%{
#include <config.h>
/* We don't need perfect functions for these tests. */
#undef malloc
#undef memcmp
#undef realloc
#include <stdio.h>

#if STDC_HEADERS
# include <stdlib.h>
# include <string.h>
#else
char *strcat(char *dest, const char *src);
#endif
#include <ctype.h>
#include <assert.h>

extern void perror (const char *s);

/* Exercise pre-prologue dependency to %union.  */
typedef int value_t;

value_t global_result = 0;
int global_count = 0;

%}

%parse-param "value_t *result", "result"
%parse-param "int *count",      "count"

/* Exercise %union. */
%union
{
  value_t ival;
};

%{
#if YYPURE
#  define LOC     (*yylloc)
#  define VAL     (*yylval)
#else
#  define LOC     (yylloc)
#  define VAL     (yylval)
#endif

#if YYPURE
#  if YYLSP_NEEDED
#    define LEX_FORMALS     YYSTYPE *yylval, YYLTYPE *yylloc
#    define LEX_ARGS        yylval, yylloc
#    define USE_LEX_ARGS    (void) yylval; (void) yylloc;
#  else
#    define LEX_FORMALS     YYSTYPE *yylval
#    define LEX_ARGS        yylval
#    define USE_LEX_ARGS    (void) yylval
#  endif
#  define LEX_PRE_FORMALS   LEX_FORMALS,
#  define LEX_PRE_ARGS      LEX_ARGS,
#else
#  define LEX_FORMALS       void
#  define LEX_PRE_FORMALS
#  define LEX_ARGS
#  define LEX_PRE_ARGS
#  define USE_LEX_ARGS
#endif

static int power (int base, int exponent);
static void yyerror (const char *s);
static int yylex (LEX_FORMALS);
static int yygetc (LEX_FORMALS);
static void yyungetc (LEX_PRE_FORMALS int c);
%}

/* Bison Declarations */
%token CALC_EOF 0 "end of input"
%token <ival> NUM "number"
%type  <ival> exp

%nonassoc '=' /* comparison	       */
%left '-' '+'
%left '*' '/'
%left NEG     /* negation--unary minus */
%right '^'    /* exponentiation        */



/* Grammar follows */
%%
input:
  line
| input line         { ++*count; ++global_count; }
;

line:
  '\n'
| exp '\n'           { *result = global_result = $1; }
;

exp:
  NUM                { $$ = $1;             }
| exp '=' exp
  {
     if ($1 != $3)
       fprintf (stderr, "calc: error: %d != %d\n", $1, $3);
     $$ = $1;
  }
| exp '+' exp        { $$ = $1 + $3;        }
| exp '-' exp        { $$ = $1 - $3;        }
| exp '*' exp        { $$ = $1 * $3;        }
| exp '/' exp        { $$ = $1 / $3;        }
| '-' exp  %prec NEG { $$ = -$2;            }
| exp '^' exp        { $$ = power ($1, $3); }
| '(' exp ')'        { $$ = $2;             }
| '(' error ')'      { $$ = 0;              }
;
%%
/* The input. */
FILE *yyin;

static void
yyerror (const char *s)
{
#if YYLSP_NEEDED
  fprintf (stderr, "%d.%d-%d.%d: ",
	   LOC.first_line, LOC.first_column,
	   LOC.last_line, LOC.last_column);
#endif
  fprintf (stderr, "%s\n", s);
}


#if YYLSP_NEEDED
static YYLTYPE last_yylloc;
#endif
static int
yygetc (LEX_FORMALS)
{
  int res = getc (yyin);
  USE_LEX_ARGS;
#if YYLSP_NEEDED
  last_yylloc = LOC;
  if (res == '\n')
    {
      LOC.last_line++;
      LOC.last_column = 1;
    }
  else
    LOC.last_column++;
#endif
  return res;
}


static void
yyungetc (LEX_PRE_FORMALS int c)
{
  USE_LEX_ARGS;
#if YYLSP_NEEDED
  /* Wrong when C == `\n'. */
  LOC = last_yylloc;
#endif
  ungetc (c, yyin);
}

static int
read_signed_integer (LEX_FORMALS)
{
  int c = yygetc (LEX_ARGS);
  int sign = 1;
  int n = 0;

  USE_LEX_ARGS;
  if (c == '-')
    {
      c = yygetc (LEX_ARGS);
      sign = -1;
    }

  while (isdigit (c))
    {
      n = 10 * n + (c - '0');
      c = yygetc (LEX_ARGS);
    }

  yyungetc (LEX_PRE_ARGS c);

  return sign * n;
}



/*---------------------------------------------------------------.
| Lexical analyzer returns an integer on the stack and the token |
| NUM, or the ASCII character read if not a number.  Skips all   |
| blanks and tabs, returns 0 for EOF.                            |
`---------------------------------------------------------------*/

static int
yylex (LEX_FORMALS)
{
  static int init = 1;
  int c;

  if (init)
    {
      init = 0;
#if YYLSP_NEEDED
      LOC.last_column = 1;
      LOC.last_line = 1;
#endif
    }

#if YYLSP_NEEDED
  LOC.first_column = LOC.last_column;
  LOC.first_line = LOC.last_line;
#endif

  /* Skip white space.  */
  while ((c = yygetc (LEX_ARGS)) == ' ' || c == '\t')
    {
#if YYLSP_NEEDED
      LOC.first_column = LOC.last_column;
      LOC.first_line = LOC.last_line;
#endif
    }

  /* process numbers   */
  if (c == '.' || isdigit (c))
    {
      yyungetc (LEX_PRE_ARGS c);
      VAL.ival = read_signed_integer (LEX_ARGS);
      return NUM;
    }

  /* Return end-of-file.  */
  if (c == EOF)
    return CALC_EOF;

  /* Return single chars. */
  return c;
}

static int
power (int base, int exponent)
{
  int res = 1;
  if (exponent < 0)
    exit (1);
  for (/* Niente */; exponent; --exponent)
    res *= base;
  return res;
}

int
main (int argc, const char **argv)
{
  value_t result = 0;
  int count = 0;
  yyin = NULL;

  if (argc == 2)
    yyin = fopen (argv[1], "r");
  else
    yyin = stdin;

  if (!yyin)
    {
      perror (argv[1]);
      exit (1);
    }

#if YYDEBUG
  yydebug = 1;
#endif
  yyparse (&result, &count);
  assert (global_result == result);
  assert (global_count  == count);

  return 0;
}