equation_module.cpp

/*
 * Copyright (C) 2000, 2013 Thierry Crozat
 *
 * 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 <http://www.gnu.org/licenses/>.
 *
 * Contact: criezy01@gmail.com
 */

#include "equation_parser.h"
#include "modules.h"
#include <math.h>
#include <ctype.h>
#include <stdio.h>
#ifdef USE_READLINE
#include <readline/readline.h>
#include <readline/history.h>
#endif

void printEquationModuleHelp(int mode) {
	switch (mode) {
	case 1:
		printf("The recognized constants are:\n");
		printf("  - PI        %f\n", M_PI);
		break;
	case 2:
		printf("The recognized functions are:\n");
		printf("  - sqrt(x)   The square root of x.\n");
		printf("  - cbrt(x)   The cubic root of x.\n");
		printf("  - pow(x, y) x raised to the power of y.\n");
		printf("  - exp(x)    The exponential of x (e raised to the power of x).\n");
		printf("  - log10(x)  The base 10 logarithm of x.\n");
		printf("  - log(x)    The natural logarithm of x.\n");
		printf("  - ln(x)     Same as log(x)\n");
		printf("  - round(x)  Round x to the nearest integer.\n");
		printf("  - ceil(x)   Round x up (the smallest integer bigger or equal to x).\n");
		printf("  - floor(x)  Round x down (the biggest integer smaller or equal to x).\n");
		printf("  - fabs(x)   Absolute value of x (x if x is positive, -x otherwise).\n");
		printf("  - abs(x)    Same as fabs(x)\n");
		printf("  - sign(x)   The sign of x (-1 for a negative value, 1 otherwise).\n");
		printf("  - cos(x)    The cosine of x.\n");
		printf("  - sin(x)    The sine of x.\n");
		printf("  - tan(x)    The tangent of x.\n");
		printf("  - asin(x)   The arc sine of x.\n");
		printf("  - acos(x)   The arc cosine of x.\n");
		printf("  - atan(x)   The arc tangent of x.\n");
		printf("  - atan2(y, x)  The angle between the x axis and the segment defined by the points (0,0)\n");
		printf("              and (x,y), which corresponds to the phase of the complex number x + iy.\n");
		printf("  - sinh(x)   The hyperbolic sine of x.\n");
		printf("  - cosh(x)   The hyperbolic cosine of x.\n");
		printf("  - tanh(x)   The hyperbolic tangent of x.\n");
		printf("  - asinh(x)  The arc hyperbolic sine of x.\n");
		printf("  - acosh(x)  The arc hyperbolic cosine of x.\n");
		printf("  - atanh(x)  The arc hyperbolic tangent of x.\n");
		printf("  - degToRad(x)  Converts an angle in degrees to radians.\n");
		printf("  - radToDeg(x)  Converts an angle in radians to degrees.\n");
		printf("  - min(x, y) The minimum of the two given values.\n");
		printf("  - max(x, y) The maximum of the two given values.\n");
		printf("  - urand(min, max)  A random number between min and max (uniform distribution).\n");
		printf("  - nrand(mean, sigma) A random number with a normal (Gaussian) distribution.\n");
		printf("  - rands(s)  Set a seed for the urand() and nrand() functions and return the seed.\n");
		printf("  - if (x, y, z) If x is true (not equal to zero) return y, otherwise return z.\n");
		printf("  - print(x [, y, \"text\", z...])  Print the passed values and strings.\n");
		break;
	case 3:
		printf("The recognized operators are:\n");
		printf("  - x + y     Add y to x.\n");
		printf("  - x - y     Substract y from x.\n");
		printf("  - x * y     Multiply x and y.\n");
		printf("  - x / y     Divide x by y.\n");
		printf("  - x %% y     Floating-point remainder of dividing x by y.\n");
		printf("  - x^y       Raise x to the power of y (same as pow(x, y)).\n");
		printf("  - +x or -x  Unary plus and minus operators (change the sign of x).\n");
		printf("  - x && y    Logical and (return true - i.e. 1 - if x and y are not null).\n");
		printf("  - x || y    Logical or (return true - i.e. 1 - if either x or y - or both - is not null).\n");
		printf("  - x == y    Test equality (return true - i.e. 1 - if x is equal to y).\n");
		printf("  - x != y    Test inequality (return true - i.e. 1 - if x and y are different).\n");
		printf("  - x < y     Return true if x is smaller than y.\n");
		printf("  - x <= y    Return true if x is smaller or equal than y.\n");
		printf("  - x > y     Return true if x is greater than y.\n");
		printf("  - x >= y    Return true if x is greater or equal than y.\n");
		printf("  - x = y     Asignement (set x to y and return y).\n");
		printf("  - x += y    Add y to x and store the result in x.\n");
		printf("  - x -= y    Substract y from x and store the result in y.\n");
		printf("  - x *= y    Multiply x and y and store the result in y.\n");
		printf("  - x /= y    Divide x by y and store the result in y.\n");
		printf("  - ++x       Prefix increment operator (add 1 to x).\n");
		printf("  - --x       Prefix decrement operator (remove 1 from x).\n");
		break;
	case 4:
		printf("The recognized debug commands are:\n");
		printf("  - tree <equation>  Prints the parser tree for the given equation.\n");
		break;
	case 5:
		printf("You can define or undefine variables that can then be used in equations:\n");
		printf("  - define VAR [value] Define a variable with the given name. A value or equation can optionally\n");
		printf("                       be specified to initialize the variable. Otherwise it is initialized to 0.\n");
		printf("  - undefine VAR       Undefine the variable with the given name.\n");
		printf("  - variables          List the defined variables.\n");
		break;
	default:
		printf("Evaluates C-like mathematical expressions.\n");
		printf("Type 'help topic' to get help on a specific topic.\n");
		printf("Topics are: 'constants', 'functions', 'operators', 'variables', 'debug'\n");
		printf("Type 'quit' or 'exit' to quit the program.\n");
		break;
	}
}

String readLine(const char* prompt, bool strip_eol) {
#ifdef USE_READLINE
	char *line = readline(prompt);
	String str = line;
	if (line != NULL && *line != 0)
		add_history(line);
	free(line);
	if (!strip_eol)
	str += "\n";
	return str;
#else
	if (prompt != NULL && *prompt != 0)
		printf("%s", prompt);
	return readLine(strip_eol, stdin);
#endif
}

String readLine(bool strip_eol, FILE* stream) {
	char buffer[256];
	String line;
	while (!feof(stream) && (line.isEmpty() || line[line.length() - 1] != '\n')) {
		if (fgets(buffer, 256, stream) != NULL)
			line += buffer;
	}
	if (strip_eol)
		return line.left(-2);
	return line;
}

void runEquationModule() {
	printf("Starting simple equation mode.\nType 'help' to get some help.\n");
	EquationParser parser;
	const int max_variables = 256;
	StringList variables;
	double variable_values[max_variables];
	while (1) {
		// Read a line
		String line = readLine("> ");
		if (line.isEmpty())
			continue;

		// Check if it is exit
		if (line == "exit" || line == "quit")
			break;

		// Check if it is help
		if (line.startsWith("help") && (line.length() == 4 || isspace(line[4]))) {
			String topic = line.right(4).trimmed();
			int t = 0;
			if (topic == "constants")
				t = 1;
			else if (topic == "functions")
				t = 2;
			else if (topic == "operators")
				t = 3;
			else if (topic == "debug")
				t = 4;
			else if (topic == "variables")
				t = 5;
			printEquationModuleHelp(t);
			continue;
		}
		
		if (line.startsWith("undefine ")) {
			String name = line.right(9).trimmed();
			int idx = variables.indexOf(name);
			if (idx != -1) {
				variables.removeAt(idx);
				for ( ; idx < variables.size() ; ++idx)
					variable_values[idx] = variable_values[idx + 1];
			} else
				printf("Variable '%s' does not exist.", name.c_str());
			continue;
		}
		
		if (line == "variables") {
			int nb = variables.size();
			switch (nb) {
			case 0:
				printf("There is no variable defined.\n");
				break;
			case 1:
				printf("There is 1 variable defined:\n");
				break;
			default:
				printf("There are %d variables defined:\n", nb);
				break;
			}
			for (int i = 0 ; i < nb ; ++i)
				printf("%s = %f\n", variables[i].c_str(), variable_values[i]);
			continue;
		}

		// Handle Equation
#ifdef PARSER_TREE_DEBUG
		bool tree_debug = false;
#endif
		int var_index = -1;
		String equation;
		if (line.startsWith("tree") && (line.length() == 4 || isspace(line[4]))) {
#ifdef PARSER_TREE_DEBUG
			equation = line.right(4).trimmed();
			tree_debug = true;
#else
			printf("The parser tree debugging feature is disabled. You need to recompile the executable with the feature enabled before you can use it.\n");
#endif
		} else if (line.startsWith("define ")) {
			String name = line.right(7).trimmed();
			int space_idx = name.findSpace();
			if (space_idx != -1) {
				equation = name.right(space_idx).trimmed();
				name = name.left(space_idx - 1);
			}
			var_index = variables.indexOf(name);
			if (var_index == -1) {
				if (variables.size() == max_variables) {
					printf("Cannot define variable %s as the maximum number of variables has been reached.", name.c_str());
					printf("You need to undefine variables before you can define new variables.");
				} else {
					var_index = variables.size();
					variables << name;
					variable_values[var_index] = 0.;
				}		
			}
		} else
			equation = line;
		if (equation.isEmpty())
			continue;

		// Parse the equation
		if (!parser.parse(equation, variables)) {
			if (parser.nbErrors() == 0)
				printf("Syntax error...\n");
			else {
				printf("Equation contains %d error(s):\n", parser.nbErrors());
				for (int error = 0 ; error < parser.nbErrors() ; ++error)
					printf("  %d: %s\n", error+1, parser.getError(error).c_str());
			}
			continue;
		}
#ifdef PARSER_TREE_DEBUG
		if (tree_debug)
			EquationParser::debugPrint(parser.getParserTreeDescription());
#endif
		double value = parser.evaluate(variable_values);
		printf("%.12g\n", value);
		if (var_index != -1)
			variable_values[var_index] = value;
	}
}