@*Intro. This is a simple filter that inputs the well-known DIMACS format for
satisfiability problems and outputs the format used by {\mc SAT0}, {\mc SAT1},
etc.

DIMACS format begins with zero or more optional comment lines, indicated by
their first character `\.c'. The next line should say `\.p \.{cnf} $n$ $m$',
where $n$ is the number of variables and $m$ is the number of clauses.
Then comes a string of $m$ ``clauses,'' which are sequences of
nonzero integers of absolute value $\le n$, followed by zero.
A literal for the $k$th variable is represented by $k$; its complement
is represented by $-k$.

SAT format is explained in the programs cited above.

@d buf_size 1024

@c
#include <stdio.h>
#include <stdlib.h>
char buf[buf_size];
int m,n,v;
main() {
  register int j,k,l,p;
  @<Read the preamble@>;
  if (m==0 || n==0) {
    fprintf(stderr,"I didn't find m or n!\n");
    exit(-1);
  }
  @<Read and translate the clauses@>;
}

@ @<Read the preamble@>=
while (1) {
  if (!fgets(buf,buf_size,stdin)) break;
  if (buf[0]=='c') @<Process a comment line and |continue|@>;
  if (buf[0]!='p' || buf[1]!=' ' ||
          buf[2]!='c' || buf[3]!='n' || buf[4]!='f') {
    fprintf(stderr,"Unrecognized input line: %s\n",buf);
    exit(-2);
  }
  sscanf(buf+5,"%i %i",&n,&m);
  break;
}

@ @<Process a comment line and |continue|@>=
{
  printf("~ %s",buf+1);
  continue;
}

@ @<Read and translate...@>=
j=k=l=p=0;
while (fscanf(stdin,"%i",&v)==1) {
  if (v==0) {
    if (j==0)
      fprintf(stderr,"Warning: Clause %d is empty!\n",k+1);
    printf("\n");
    if (k==m) {
      fprintf(stderr,"Too many clauses (more than %d)!\n",m);
      exit(-3);
    }
    k++,j=0;
  }@+else if (v>0) {
    if (v>n) {
      fprintf(stderr,"Too many variables (%d > %d)!\n",v,n);
      exit(-4);
    }
    printf(" %d",v);
    if (v>p) p=v;
    j++,l++;
  }@+else {
    if (v<-n) {
      fprintf(stderr,"Too many variables (%d < -%d)!\n",v,n);
      exit(-5);
    }
    printf(" ~%d",-v);
    if (-v>p) p=-v;
    j++,l++;
  }
}
if (j) {
  fprintf(stderr,"The last clause didn't end with 0!\n");
  printf("\n");
  k++;
}  
if (k<m) fprintf(stderr,"Too few clauses (%d < %d)!\n",k,m);
fprintf(stderr,"OK, I wrote out %d literals in %d clauses on %d variables.\n",
           l,k,p);

@*Index.