197 lines
6.2 KiB
C++
197 lines
6.2 KiB
C++
/*
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This file is part of libeval, a simple math expression evaluator
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Copyright (C) 2017 Michael Geselbracht, mgeselbracht3@gmail.com
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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/*
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An evaluator object is used to replace an input string that represents
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a mathematical expression by its result.
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Example: Consider the input "3+4". The result of this expression is "7".
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The NumericEvaluator can be used like this:
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NumericEvaluator eval;
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eval.process("3+4");
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printf("3+4", eval.result());
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The same example with error checking. Please note that even a valid input string may result
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in an empty output string or "NaN".
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NumericEvaluator eval;
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bool ret = eval.process("3+4");
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assert(ret == eval.isValid()); // isValid() reflects return value of process().
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if (eval.isValid()) printf("3+4=%s\n", eval.result());
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Using variables
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Expressions can refer to variables if they were defined by previous expressions.
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A variable can be defined by an expression or by the setVar() method.
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Expressions that define/set variables do not have a result.
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eval.process("x=1; y=2"); // Result is NaN
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eval.setVar("z", 3);
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eval.process("x+y+z");
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printf("x+y+z=%s\n", eval.result());
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Input string storage
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An evaluator object can store and retrieve the original input string using a pointer
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as key. This can be used to restore the input string of a text entry field.
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eval.process("25.4-0.7", &eval);
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printf("%s = %s\n", eval.textInput(&eval), eval.result());
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Unit conversion
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The evaluator uses a default unit and constants can be specified with a unit.
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As long as no units are used the default unit is not relevant. The default
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unit is taken from the global (Kicad) variable g_UserUnit.
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Supported units are millimeters (mm), Mil (mil) and inch (")
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eval.process("1\"");
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printf("1\" = %s\n", eval.result());
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eval.process("12.7 - 0.1\" - 50mil");
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printf("12.7 - 0.1\" - 50mil = %s\n", eval.result());
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*/
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#ifndef NUMERIC_EVALUATOR_H_
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#define NUMERIC_EVALUATOR_H_
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#include "grammar.h"
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#include <stddef.h>
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#include <string>
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#include <string>
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#include <map>
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// This namespace is used for the lemon parser
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namespace numEval
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{
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struct TokenType
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{
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union {
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double dValue;
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int iValue;
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};
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bool valid;
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char text[32];
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};
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} // namespace numEval
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class NumericEvaluator {
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enum class Unit { Invalid, Metric, Inch, Mil };
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public:
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NumericEvaluator();
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~NumericEvaluator();
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/* Initialization and destruction. init() is invoked be the constructor and should not be needed
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* by the user.
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* clear() should be invoked by the user if a new input string is to be processed. It will reset
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* the parser and clear the original expression value for a requested object (if pObj != null).
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*/
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void init();
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void clear(const void* pObj = nullptr);
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/* Set the decimal separator for the input string. Defaults to '.' */
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void setDecimalSeparator(char sep);
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/* Enable or disable support for input string storage.
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* If enabled the input string is saved if process(const char*, const void*) is used.
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*/
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void enableTextInputStorage(bool w) { bClTextInputStorage = w; }
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/* Used by the lemon parser */
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void parseError(const char* s);
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void parseOk();
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void parseSetResult(double);
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/* Check if previous invokation of process() was successful */
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inline bool isValid() const { return !bClError; }
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/* Result of string processing. Undefined if !isValid() */
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inline const char* result() const { return clToken.token; }
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/* Evaluate input string.
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* Result can be retrieved by result().
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* Returns true if input string could be evaluated, otherwise false.
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*/
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bool process(const char* s);
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/* Like process(const char*) but also stores input string in a std:map with key pObj. */
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bool process(const char* s, const void* pObj);
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/* Retrieve old input string with key pObj. */
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const char* textInput(const void* pObj) const;
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/* Add/set variable with value */
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void setVar(const std::string&, double value);
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/* Get value of variable. Returns 0.0 if not defined. */
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double getVar(const std::string&);
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/* Remove single variable */
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void removeVar(const std::string& s) { clVarMap.erase(s); }
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/* Remove all variables */
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void clearVar() { clVarMap.clear(); }
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protected:
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/* Token type used by the tokenizer */
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struct Token {
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int token;
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numEval::TokenType value;
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};
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/* Begin processing of a new input string */
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void newString(const char* s);
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/* Tokenizer: Next token/value taken from input string. */
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Token getToken();
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/* Used by processing loop */
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void parse(int token, numEval::TokenType value);
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private:
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void* pClParser; // the current lemon parser state machine
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/* Token state for input string. */
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struct TokenStat {
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enum { OutLen=32 };
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TokenStat() : input(0), token(0), inputLen(0), pos(0) { /* empty */ }
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const char* input; // current input string ("var=4")
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char* token; // output token ("var", type:VAR; "4", type:VALUE)
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size_t inputLen; // strlen(input)
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size_t pos; // current index
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} clToken;
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char cClDecSep; // decimal separator ('.')
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/* Parse progress. Set by parser actions. */
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bool bClError;
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bool bClParseFinished;
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bool bClTextInputStorage; // Enable input string storage used by process(const char*, const void*)
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Unit eClUnitDefault; // Default unit for values
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std::map<const void*, std::string> clObjMap; // Map pointer to text entry -> (original) input string
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std::map<std::string, double> clVarMap;
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};
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#endif /* NUMERIC_EVALUATOR_H_ */
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