numeric_evaluator.h

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/*
 This file is part of libeval, a simple math expression evaluator
 
 Copyright (C) 2017 Michael Geselbracht, [email protected]
 
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
 
/*
An evaluator object is used to replace an input string that represents
a mathematical expression by its result.
 
Example: Consider the input "3+4". The result of this expression is "7".
The NumericEvaluator can be used like this:
 
 NumericEvaluator eval;
 eval.process("3+4");
 printf("3+4", eval.result());
 
The same example with error checking. Please note that even a valid input string may result
in an empty output string or "NaN".
 
 NumericEvaluator eval;
 bool ret = eval.process("3+4");
 assert(ret == eval.isValid()); // isValid() reflects return value of process().
 if (eval.isValid()) printf("3+4=%s\n", eval.result());
 
Using variables
Expressions can refer to variables if they were defined by previous expressions.
A variable can be defined by an expression or by the setVar() method.
Expressions that define/set variables do not have a result.
 
 eval.process("x=1; y=2"); // Result is NaN
 eval.setVar("z", 3);
 eval.process("x+y+z");
 printf("x+y+z=%s\n", eval.result());
 
Input string storage
An evaluator object can store and retrieve the original input string using a pointer
as key. This can be used to restore the input string of a text entry field.
 
 eval.process("25.4-0.7", &eval);
 printf("%s = %s\n", eval.textInput(&eval), eval.result());
 
Unit conversion
The evaluator uses a default unit and constants can be specified with a unit.
As long as no units are used the default unit is not relevant.
Supported units are millimeters (mm), Mil (mil) and inch (")
 
 eval.process("1\"");
 printf("1\" = %s\n", eval.result());
 eval.process("12.7 - 0.1\" - 50mil");
 printf("12.7 - 0.1\" - 50mil = %s\n", eval.result());
*/
 
#ifndef NUMERIC_EVALUATOR_H_
#define NUMERIC_EVALUATOR_H_
 
#include <cstddef>
#include <map>
#include <string>
 
#include <eda_units.h>
 
// This namespace is used for the lemon parser
namespace numEval
{
 struct TokenType
 {
 union
 {
 double dValue;
 int iValue;
 };
 
 bool valid;
 char text[32];
 };
 
} // namespace numEval
 
class NUMERIC_EVALUATOR
{
 enum class Unit { Invalid, UM, MM, CM, Inch, Mil, Degrees, SI };
 
public:
 NUMERIC_EVALUATOR( EDA_UNITS aUnits );
 ~NUMERIC_EVALUATOR();
 
 /* clear() should be invoked by the client if a new input string is to be processed. It
 * will reset the parser. User defined variables are retained.
 */
 void Clear();
 
 void SetDefaultUnits( EDA_UNITS aUnits );
 
 void LocaleChanged();
 
 /* Used by the lemon parser */
 void parseError(const char* s);
 void parseOk();
 void parseSetResult(double);
 
 /* Check if previous invocation of process() was successful */
 inline bool IsValid() const { return !m_parseError; }
 
 /* Result of string processing. Undefined if !isValid() */
 inline wxString Result() const { return wxString::FromUTF8( m_token.token ); }
 
 /* Evaluate input string.
 * Result can be retrieved by result().
 * Returns true if input string could be evaluated, otherwise false.
 */
 bool Process( const wxString& aString );
 
 /* Retrieve the original text before evaluation. */
 wxString OriginalText() const;
 
 /* Add/set variable with value */
 void SetVar( const wxString& aString, double aValue );
 
 /* Get value of variable. Returns 0.0 if not defined. */
 double GetVar( const wxString& aString );
 
 /* Remove single variable */
 void RemoveVar( const wxString& aString ) { m_varMap.erase( aString ); }
 
 /* Remove all variables */
 void ClearVar() { m_varMap.clear(); }
 
protected:
 /* Token type used by the tokenizer */
 struct Token
 {
 int token;
 numEval::TokenType value;
 };
 
 /* Begin processing of a new input string */
 void newString( const wxString& aString );
 
 /* Tokenizer: Next token/value taken from input string. */
 Token getToken();
 
 /* Used by processing loop */
 void parse( int token, numEval::TokenType value );
 
private:
 void* m_parser; // the current lemon parser state machine
 
 /* Token state for input string. */
 struct TokenStat
 {
 TokenStat() :
 input( nullptr ),
 token( nullptr ),
 inputLen( 0 ),
 outputLen( 0 ),
 pos( 0 )
 {};
 
 const char* input; // current input string ("var=4")
 char* token; // output token ("var", type:VAR; "4", type:VALUE)
 size_t inputLen; // strlen(input)
 size_t outputLen; // At least 64, up to input length
 size_t pos; // current index
 } m_token;
 
 char m_localeDecimalSeparator;
 
 /* Parse progress. Set by parser actions. */
 bool m_parseError;
 bool m_parseFinished;
 
 Unit m_defaultUnits; // Default unit for values
 
 wxString m_originalText;
 
 std::map<wxString, double> m_varMap;
};
 
 
#endif /* NUMERIC_EVALUATOR_H_ */