1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
// Copyright 2016 ALRUX Inc.
//
// 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.
package levenshtein
// Params represents a set of parameter values for the various formulas involved
// in the calculation of the Levenshtein string metrics.
type Params struct {
insCost int
subCost int
delCost int
maxCost int
minScore float64
bonusPrefix int
bonusScale float64
bonusThreshold float64
}
var (
defaultParams = NewParams()
)
// NewParams creates a new set of parameters and initializes it with the default values.
func NewParams() *Params {
return &Params{
insCost: 1,
subCost: 1,
delCost: 1,
maxCost: 0,
minScore: 0,
bonusPrefix: 4,
bonusScale: .1,
bonusThreshold: .7,
}
}
// Clone returns a pointer to a copy of the receiver parameter set, or of a new
// default parameter set if the receiver is nil.
func (p *Params) Clone() *Params {
if p == nil {
return NewParams()
}
return &Params{
insCost: p.insCost,
subCost: p.subCost,
delCost: p.delCost,
maxCost: p.maxCost,
minScore: p.minScore,
bonusPrefix: p.bonusPrefix,
bonusScale: p.bonusScale,
bonusThreshold: p.bonusThreshold,
}
}
// InsCost overrides the default value of 1 for the cost of insertion.
// The new value must be zero or positive.
func (p *Params) InsCost(v int) *Params {
if v >= 0 {
p.insCost = v
}
return p
}
// SubCost overrides the default value of 1 for the cost of substitution.
// The new value must be zero or positive.
func (p *Params) SubCost(v int) *Params {
if v >= 0 {
p.subCost = v
}
return p
}
// DelCost overrides the default value of 1 for the cost of deletion.
// The new value must be zero or positive.
func (p *Params) DelCost(v int) *Params {
if v >= 0 {
p.delCost = v
}
return p
}
// MaxCost overrides the default value of 0 (meaning unlimited) for the maximum cost.
// The calculation of Distance() stops when the result is guaranteed to exceed
// this maximum, returning a lower-bound rather than exact value.
// The new value must be zero or positive.
func (p *Params) MaxCost(v int) *Params {
if v >= 0 {
p.maxCost = v
}
return p
}
// MinScore overrides the default value of 0 for the minimum similarity score.
// Scores below this threshold are returned as 0 by Similarity() and Match().
// The new value must be zero or positive. Note that a minimum greater than 1
// can never be satisfied, resulting in a score of 0 for any pair of strings.
func (p *Params) MinScore(v float64) *Params {
if v >= 0 {
p.minScore = v
}
return p
}
// BonusPrefix overrides the default value for the maximum length of
// common prefix to be considered for bonus by Match().
// The new value must be zero or positive.
func (p *Params) BonusPrefix(v int) *Params {
if v >= 0 {
p.bonusPrefix = v
}
return p
}
// BonusScale overrides the default value for the scaling factor used by Match()
// in calculating the bonus.
// The new value must be zero or positive. To guarantee that the similarity score
// remains in the interval 0..1, this scaling factor is not allowed to exceed
// 1 / BonusPrefix.
func (p *Params) BonusScale(v float64) *Params {
if v >= 0 {
p.bonusScale = v
}
// the bonus cannot exceed (1-sim), or the score may become greater than 1.
if float64(p.bonusPrefix)*p.bonusScale > 1 {
p.bonusScale = 1 / float64(p.bonusPrefix)
}
return p
}
// BonusThreshold overrides the default value for the minimum similarity score
// for which Match() can assign a bonus.
// The new value must be zero or positive. Note that a threshold greater than 1
// effectively makes Match() become the equivalent of Similarity().
func (p *Params) BonusThreshold(v float64) *Params {
if v >= 0 {
p.bonusThreshold = v
}
return p
}
|
