OR-Tools  8.2
lp_print_utils.cc
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1 // Copyright 2010-2018 Google LLC
2 // Licensed under the Apache License, Version 2.0 (the "License");
3 // you may not use this file except in compliance with the License.
4 // You may obtain a copy of the License at
5 //
6 // http://www.apache.org/licenses/LICENSE-2.0
7 //
8 // Unless required by applicable law or agreed to in writing, software
9 // distributed under the License is distributed on an "AS IS" BASIS,
10 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
11 // See the License for the specific language governing permissions and
12 // limitations under the License.
13 
15 
16 #include <cmath>
17 #include <cstdio>
18 #include <limits>
19 
20 #include "absl/strings/str_cat.h"
22 #include "ortools/base/logging.h"
25 
26 namespace operations_research {
27 namespace glop {
28 
29 // Returns a string "num/den" representing the rational approximation of x.
30 // The absolute difference between the output fraction and the input "x" will
31 // not exceed "precision".
32 std::string StringifyRational(const double x, const double precision) {
33  if (x == kInfinity) {
34  return "inf";
35  } else if (x == -kInfinity) {
36  return "-inf";
37  }
38  Fraction fraction = RationalApproximation(x, precision);
39  const int64 numerator = fraction.first;
40  const int64 denominator = fraction.second;
41  return denominator == 1 ? absl::StrCat(numerator)
42  : absl::StrCat(numerator, "/", denominator);
43 }
44 
45 std::string Stringify(const Fractional x, bool fraction) {
46  return fraction ? StringifyRational(ToDouble(x),
47  std::numeric_limits<double>::epsilon())
48  : Stringify(x);
49 }
50 
51 // Returns a string that pretty-prints a monomial ax with coefficient
52 // a and variable name x
53 std::string StringifyMonomial(const Fractional a, const std::string& x,
54  bool fraction) {
55  if (a == 0.0) return "";
56  return a > 0.0
57  ? absl::StrCat(
58  " + ",
59  a == 1.0 ? x : absl::StrCat(Stringify(a, fraction), " ", x))
60  : absl::StrCat(
61  " - ", a == -1.0
62  ? x
63  : absl::StrCat(Stringify(-a, fraction), " ", x));
64 }
65 
66 } // namespace glop
67 } // namespace operations_research
int64_t int64
std::string StringifyMonomial(const Fractional a, const std::string &x, bool fraction)
std::string Stringify(const Fractional x, bool fraction)
std::string StringifyRational(const double x, const double precision)
const double kInfinity
Definition: lp_types.h:83
static double ToDouble(double f)
Definition: lp_types.h:68
The vehicle routing library lets one model and solve generic vehicle routing problems ranging from th...
std::pair< int64, int64 > Fraction
Fraction RationalApproximation(const double x, const double precision)