KiCad PCB EDA Suite
numeric_evaluator.h
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1 /*
2  This file is part of libeval, a simple math expression evaluator
3 
4  Copyright (C) 2017 Michael Geselbracht, mgeselbracht3@gmail.com
5 
6  This program is free software: you can redistribute it and/or modify
7  it under the terms of the GNU General Public License as published by
8  the Free Software Foundation, either version 3 of the License, or
9  (at your option) any later version.
10 
11  This program is distributed in the hope that it will be useful,
12  but WITHOUT ANY WARRANTY; without even the implied warranty of
13  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14  GNU General Public License for more details.
15 
16  You should have received a copy of the GNU General Public License
17  along with this program. If not, see <https://www.gnu.org/licenses/>.
18 */
19 
20 /*
21 An evaluator object is used to replace an input string that represents
22 a mathematical expression by its result.
23 
24 Example: Consider the input "3+4". The result of this expression is "7".
25 The NumericEvaluator can be used like this:
26 
27  NumericEvaluator eval;
28  eval.process("3+4");
29  printf("3+4", eval.result());
30 
31 The same example with error checking. Please note that even a valid input string may result
32 in an empty output string or "NaN".
33 
34  NumericEvaluator eval;
35  bool ret = eval.process("3+4");
36  assert(ret == eval.isValid()); // isValid() reflects return value of process().
37  if (eval.isValid()) printf("3+4=%s\n", eval.result());
38 
39 Using variables
40 Expressions can refer to variables if they were defined by previous expressions.
41 A variable can be defined by an expression or by the setVar() method.
42 Expressions that define/set variables do not have a result.
43 
44  eval.process("x=1; y=2"); // Result is NaN
45  eval.setVar("z", 3);
46  eval.process("x+y+z");
47  printf("x+y+z=%s\n", eval.result());
48 
49 Input string storage
50 An evaluator object can store and retrieve the original input string using a pointer
51 as key. This can be used to restore the input string of a text entry field.
52 
53  eval.process("25.4-0.7", &eval);
54  printf("%s = %s\n", eval.textInput(&eval), eval.result());
55 
56 Unit conversion
57 The evaluator uses a default unit and constants can be specified with a unit.
58 As long as no units are used the default unit is not relevant.
59 Supported units are millimeters (mm), Mil (mil) and inch (")
60 
61  eval.process("1\"");
62  printf("1\" = %s\n", eval.result());
63  eval.process("12.7 - 0.1\" - 50mil");
64  printf("12.7 - 0.1\" - 50mil = %s\n", eval.result());
65 */
66 
67 #ifndef NUMERIC_EVALUATOR_H_
68 #define NUMERIC_EVALUATOR_H_
69 
70 #include <cstddef>
71 #include <map>
72 #include <string>
73 
74 #include <base_units.h>
75 
76 // This namespace is used for the lemon parser
77 namespace numEval
78 {
79 
80  struct TokenType
81  {
82  union
83  {
84  double dValue;
85  int iValue;
86  };
87 
88  bool valid;
89  char text[32];
90  };
91 
92 } // namespace numEval
93 
95 {
96  enum class Unit { Invalid, Metric, Inch, Mil };
97 
98 public:
99  NUMERIC_EVALUATOR( EDA_UNITS aUnits, bool aUseMils = false );
101 
102  /* clear() should be invoked by the client if a new input string is to be processed. It
103  * will reset the parser. User defined variables are retained.
104  */
105  void Clear();
106 
107  /* Used by the lemon parser */
108  void parseError(const char* s);
109  void parseOk();
110  void parseSetResult(double);
111 
112  /* Check if previous invokation of process() was successful */
113  inline bool IsValid() const { return !m_parseError; }
114 
115  /* Result of string processing. Undefined if !isValid() */
116  inline wxString Result() const { return wxString::FromUTF8( m_token.token ); }
117 
118  /* Evaluate input string.
119  * Result can be retrieved by result().
120  * Returns true if input string could be evaluated, otherwise false.
121  */
122  bool Process( const wxString& aString );
123 
124  /* Retrieve the original text before evaluation. */
125  wxString OriginalText() const;
126 
127  /* Add/set variable with value */
128  void SetVar( const wxString& aString, double aValue );
129 
130  /* Get value of variable. Returns 0.0 if not defined. */
131  double GetVar( const wxString& aString );
132 
133  /* Remove single variable */
134  void RemoveVar( const wxString& aString ) { m_varMap.erase( aString ); }
135 
136  /* Remove all variables */
137  void ClearVar() { m_varMap.clear(); }
138 
139 protected:
140  /* Token type used by the tokenizer */
141  struct Token
142  {
143  int token;
145  };
146 
147  /* Begin processing of a new input string */
148  void newString( const wxString& aString );
149 
150  /* Tokenizer: Next token/value taken from input string. */
151  Token getToken();
152 
153  /* Used by processing loop */
154  void parse( int token, numEval::TokenType value );
155 
156 private:
157  void* m_parser; // the current lemon parser state machine
158 
159  /* Token state for input string. */
160  struct TokenStat
161  {
162  enum { OutLen = 32 };
163  TokenStat() : input( 0 ), token( 0 ), inputLen( 0 ), pos( 0 ) { /* empty */ }
164  const char* input; // current input string ("var=4")
165  char* token; // output token ("var", type:VAR; "4", type:VALUE)
166  size_t inputLen; // strlen(input)
167  size_t pos; // current index
168  }
169  m_token;
170 
172 
173  /* Parse progress. Set by parser actions. */
176 
177  Unit m_defaultUnits; // Default unit for values
178 
179  wxString m_originalText;
180 
181  std::map<wxString, double> m_varMap;
182 };
183 
184 
185 #endif /* NUMERIC_EVALUATOR_H_ */
EDA_UNITS
Definition: common.h:196
std::map< wxString, double > m_varMap
void SetVar(const wxString &aString, double aValue)
Implementation of conversion functions that require both schematic and board internal units.
struct NUMERIC_EVALUATOR::TokenStat m_token
wxString OriginalText() const
numEval::TokenType value
bool Process(const wxString &aString)
void RemoveVar(const wxString &aString)
void parse(int token, numEval::TokenType value)
void parseSetResult(double)
void newString(const wxString &aString)
wxString Result() const
NUMERIC_EVALUATOR(EDA_UNITS aUnits, bool aUseMils=false)
double GetVar(const wxString &aString)
void parseError(const char *s)