kicad/include/libeval/numeric_evaluator.h

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2017-11-23 10:36:24 +00:00
/*
This file is part of libeval, a simple math expression evaluator
Copyright (C) 2017 Michael Geselbracht, mgeselbracht3@gmail.com
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. The default
unit is taken from the global (Kicad) variable g_UserUnit.
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 "grammar.h"
#include <stddef.h>
#include <string>
#include <string>
#include <map>
// 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 NumericEvaluator {
enum class Unit { Invalid, Metric, Inch, Mil };
public:
NumericEvaluator();
~NumericEvaluator();
/* Initialization and destruction. init() is invoked be the constructor and should not be needed
* by the user.
* clear() should be invoked by the user if a new input string is to be processed. It will reset
* the parser. User defined variables are retained.
*/
void init();
void clear();
/* Set the decimal separator for the input string. Defaults to '.' */
void setDecimalSeparator(char sep);
/* Enable or disable support for input string storage.
* If enabled the input string is saved if process(const char*, const void*) is used.
*/
void enableTextInputStorage(bool w) { bClTextInputStorage = w; }
/* Used by the lemon parser */
void parse(int token, numEval::TokenType value);
void parseError(const char* s);
void parseOk();
void parseSetResult(double);
/* Check if previous invokation of process() was successful */
inline bool isValid() const { return !bClError; }
/* Result of string processing. Undefined if !isValid() */
inline const char* result() const { return clToken.token; }
/* Evaluate input string.
* Result can be retrieved by result().
* Returns true if input string could be evaluated, otherwise false.
*/
bool process(const char* s);
/* Like process(const char*) but also stores input string in a std:map with key pObj. */
bool process(const char* s, const void* pObj);
/* Retrieve old input string with key pObj. */
const char* textInput(const void* pObj) const;
/* Add/set variable with value */
void setVar(const std::string&, double value);
/* Get value of variable. Returns 0.0 if not defined. */
double getVar(const std::string&);
/* Remove single variable */
void removeVar(const std::string& s) { clVarMap.erase(s); }
/* Remove all variables */
void clearVar() { clVarMap.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 char* s);
/* Tokenizer: Next token/value taken from input string. */
Token getToken();
private:
void* pClParser; // the current lemon parser state machine
/* Token state for input string. */
struct TokenStat {
enum { OutLen=32 };
TokenStat() : input(0), token(0), inputLen(0) { /* empty */ }
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 pos; // current index
} clToken;
char cClDecSep; // decimal separator ('.')
/* Parse progress. Set by parser actions. */
bool bClError;
bool bClParseFinished;
bool bClTextInputStorage; // Enable input string storage used by process(const char*, const void*)
Unit eClUnitDefault; // Default unit for values
std::map<const void*, std::string> clObjMap; // Map pointer to text entry -> (original) input string
std::map<std::string, double> clVarMap;
};
#endif /* NUMERIC_EVALUATOR_H_ */