meankondo/src/rational_int.c

/*
Copyright 2015 Ian Jauslin

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

#ifndef RATIONAL_AS_FLOAT

#include "rational_int.h"
#include <stdio.h>
#include <stdlib.h>
#include "istring.h"
#include "array.h"

Q quot(long int p, long int q){
  Q ret;
  if(q==0){
    fprintf(stderr,"error: %ld/%ld is ill defined\n",p,q);
    exit(-1);
  }
  ret.numerator=p;
  ret.denominator=q;
  return(ret);
}

// add
Q Q_add(Q x1,Q x2){
  Q ret;
  ret.denominator=lcm(x1.denominator,x2.denominator);
  ret.numerator=x1.numerator*(ret.denominator/x1.denominator)+x2.numerator*(ret.denominator/x2.denominator);
  return(Q_simplify(ret));
}
//multiply
Q Q_prod(Q x1,Q x2){
  return(Q_simplify(quot(x1.numerator*x2.numerator,x1.denominator*x2.denominator)));
}
// inverse
Q Q_inverse(Q x1){
  if(x1.numerator>0){
    return(quot(x1.denominator,x1.numerator));
  }
  else if(x1.numerator<0){
    return(quot(-x1.denominator,-x1.numerator));
  }
  else{
    fprintf(stderr,"error: attempting to invert %ld/%ld\n",x1.numerator, x1.denominator);
    exit(-1);
  }
    
}
// quotient
Q Q_quot(Q x1, Q x2){
  if(x2.numerator>0){
    return(Q_simplify(quot(x1.numerator*x2.denominator,x1.denominator*x2.numerator)));
  }
  else if(x2.numerator<0){
    return(Q_simplify(quot(-x1.numerator*x2.denominator,-x1.denominator*x2.numerator)));
  }
  else{
    fprintf(stderr,"error: attempting to invert %ld/%ld\n",x2.numerator, x2.denominator);
    exit(-1);
  }
}

// compare
int Q_cmp(Q x1, Q x2){
  Q quo=Q_quot(x1,x2);
  if(quo.numerator > quo.denominator){
    return(1);
  }
  else if(quo.numerator < quo.denominator){
    return(-1);
  }
  else{
    return(0);
  }
}

// simplify
Q Q_simplify(Q x){
  return(quot(x.numerator/gcd(x.numerator,x.denominator),x.denominator/gcd(x.numerator,x.denominator)));
}
//simplify in place
int Q_simplify_inplace(Q* x){
  Q ret=Q_simplify(*x);
  *x=ret;
  return(0);
}

// greatest common divisor
long int gcd(long int x, long int y){
  long int ax=labs(x);
  long int ay=labs(y);
  int security=0;
  while(ax!=0 && ay!=0){
    if(ax>ay){ax=ax%ay;}
    else{ay=ay%ax;}

    security++;
    if(security>1000000){
      fprintf(stderr,"error: could not compute gcd( %ld , %ld ) after %d tries\n",x,y,security);
      exit(-1);
    }
  }
  // if both are negative, gcd should be negative (useful for simplification of fractions and product of square roots)
  if(x<0 && y<0){
    ax*=-1;
    ay*=-1;
  }
  if(labs(ay)>labs(ax)){return(ay);}
  else{return(ax);}
}

// least common multiple
long int lcm(long int x,long int y){
  if(x!=0 || y!=0){
    return((x*y)/gcd(x,y));
  }
  else{
    return(0);
  }
}

// approximate value as double
double Q_double_value(Q q){
  return(1.0*q.numerator/q.denominator);
}


// print to string
int Q_sprint(Q num, Char_Array* out){
  if(num.denominator!=1){
    char_array_snprintf(out,"%ld/%ld", num.numerator,num.denominator);
  }
  else{
    char_array_snprintf(out,"%ld",num.numerator);
  }

  return(0);
}

#define PP_NUMERATOR_MODE 1
#define PP_DENOMINATOR_MODE 2
// read from a string
int str_to_Q(char* str, Q* num){
  char* ptr;
  int mode;
  char* buffer=calloc(str_len(str)+1,sizeof(char));
  char* buffer_ptr=buffer;

  *num=quot(0,1);

  mode=PP_NUMERATOR_MODE;
  for(ptr=str;*ptr!='\0';ptr++){
    if(*ptr=='/'){
      sscanf(buffer,"%ld",&((*num).numerator));
      buffer_ptr=buffer;
      *buffer_ptr='\0';
      mode=PP_DENOMINATOR_MODE;
    }
    else{
      buffer_ptr=str_addchar(buffer_ptr,*ptr);
    }
  }

  // last step
  if(mode==PP_NUMERATOR_MODE){
    sscanf(buffer,"%ld",&((*num).numerator));
  }
  else if(mode==PP_DENOMINATOR_MODE){
    sscanf(buffer,"%ld",&((*num).denominator));
  }

  free(buffer);
  return(0);
}

#else
int null_declaration_so_that_the_compiler_does_not_complain;
#endif