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Diffstat (limited to 'expr.c')
| -rw-r--r-- | expr.c | 242 |
1 files changed, 242 insertions, 0 deletions
@@ -0,0 +1,242 @@ +/* + * HardInfo - Displays System Information + * Copyright (C) 2003-2006 Leandro A. F. Pereira <leandro@linuxmag.com.br> + * + * 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, version 2. + * + * 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, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + */ +/* + * This is only used to compute sensor values, hence the only variable supported is '@'. + * The '`' operator (ln(x)) is not available, nor multi-line formulas. + */ + +#include <glib.h> +#include <string.h> +#include <stdio.h> +#include <ctype.h> +#include <math.h> +#include <expr.h> + +static MathToken *new_operator(gchar op) +{ + MathToken *t = g_new0(MathToken, 1); + + t->val.op = op; + t->type = TOKEN_OPERATOR; /* operator */ + + return t; +} + +static MathToken *new_variable(gchar var) +{ + MathToken *t = g_new0(MathToken, 1); + + t->val.op = '@'; + t->type = TOKEN_VARIABLE; /* variable */ + + return t; +} + +static MathToken *new_value(gfloat value) +{ + MathToken *t = g_new0(MathToken, 1); + + t->val.value = value; + t->type = TOKEN_VALUE; /* value */ + + return t; +} + +static inline gint priority(char operation) +{ + switch (operation) { + case '^': + return 3; + case '*': + case '/': + return 2; + case '+': + case '-': + return 1; + case '(': + return 0; + } + + return 0; +} + +GSList *math_infix_to_postfix(GSList *infix) +{ + MathToken *stack[500]; + gint t_sp = 0; + + GSList *postfix = NULL, *p; + MathToken *top; + + for (p = infix; p; p = p->next) { + MathToken *t = (MathToken *) p->data; + + if (t->type == TOKEN_OPERATOR && t->val.op == '(') { + stack[++t_sp] = t; + } else if (t->type == TOKEN_OPERATOR && t->val.op == ')') { + for (top = stack[t_sp]; t_sp != 0 && top->val.op != '('; top = stack[t_sp]) + postfix = g_slist_append(postfix, stack[t_sp--]); + t_sp--; + } else if (t->type != TOKEN_OPERATOR) { + postfix = g_slist_append(postfix, t); + } else if (t_sp == 0) { + stack[++t_sp] = t; + } else { + while (t_sp != 0 && priority(t->val.op) <= priority(stack[t_sp]->val.op)) + postfix = g_slist_append(postfix, stack[t_sp--]); + stack[++t_sp] = t; + } + } + + while (t_sp) + postfix = g_slist_append(postfix, stack[t_sp--]); + + return postfix; +} + +static inline gfloat __result(gfloat op1, gfloat op2, gchar operation) +{ + switch (operation) { + case '^': + return powf(op1, op2); + case '+': + return op1 + op2; + case '-': + return op1 - op2; + case '/': + return op1 / op2; + case '*': + return op1 * op2; + } + + return 0; +} + +gfloat math_postfix_eval(GSList *postfix, gfloat at_value) +{ + GSList *p; + gfloat stack[500]; + gint sp = 0; + + memset(stack, 0, sizeof(gfloat) * 500); + + for (p = postfix; p; p = p->next) { + MathToken *t = (MathToken *) p->data; + + if (t->type == TOKEN_VARIABLE) { + stack[++sp] = at_value; + } else if (t->type == TOKEN_VALUE) { + stack[++sp] = t->val.value; + } else { + gfloat op1, op2; + + op2 = stack[sp--]; + op1 = stack[sp]; + + stack[sp] = __result(op1, op2, t->val.op); + } + } + + return stack[sp]; +} + +GSList *math_string_to_infix(gchar *string) +{ + GSList *infix = NULL; + gchar *expr = string; + + for (; *expr; expr++) { + if (strchr("+-/*^()", *expr)) { + infix = g_slist_append(infix, new_operator(*expr)); + } else if (strchr("@", *expr)) { + infix = g_slist_append(infix, new_variable(*expr)); + } else if (strchr("-.1234567890", *expr)) { + gfloat value; + + sscanf(expr, "%f", &value); + + while (*expr && strchr(".1234567890", *expr)) + expr++; + expr--; + + infix = g_slist_append(infix, new_value(value)); + } else if (!isspace(*expr)) { + g_print("Invalid token: [%c][%d]\n", *expr, *expr); + math_infix_free(infix, TRUE); + return NULL; + } + } + + return infix; +} + +void math_infix_free(GSList *infix, gboolean free_tokens) +{ + GSList *p; + + if (!free_tokens) + for (p = infix; p; p = g_slist_delete_link(p, p)); + else + for (p = infix; p; p = g_slist_delete_link(p, p)) { + MathToken *t = (MathToken *)p->data; + g_free(t); + } +} + +GSList *math_string_to_postfix(gchar *string) +{ + GSList *infix; + GSList *postfix; + + infix = math_string_to_infix(string); + if (!infix) + return NULL; + + postfix = math_infix_to_postfix(infix); + math_infix_free(infix, FALSE); + + return postfix; +} + +gfloat math_string_eval(gchar *string, gfloat at_value) +{ + GSList *postfix; + gfloat val; + + postfix = math_string_to_postfix(string); + val = math_postfix_eval(postfix, at_value); + math_postfix_free(postfix, TRUE); + + return val; +} + +#ifdef MATH_TEST +int main(void) +{ + GSList *postfix; + + gchar *expr = "0.9*(@+(5.2*0.923+3*(2.0)))"; + + postfix = math_string_to_postfix(expr); + g_print("%s = %f (must be 18.71964)\n", expr, + math_postfix_eval(postfix, 10)); + math_postfix_free(postfix, TRUE); + + return 0; +} +#endif |