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view lwlib/lw_expr.h @ 434:052c5f335a92
Fix bug in like terms collection in expression simplification
Like term collection would lose the actual "variable" part of the term if
the second term collected happened to have no coefficient. This would cause
the expression to take the value of the calculated coefficient which is
obviously wrong.
Thanks to hider <stego@satx.rr.com> for reporting the bug and providing a
proper test case.
Observation: this bug has been present since the first pre-release of
lwtools 3.0 when the algebraic expression system was introduced. Apparently
people tend not to create expressions that trigger the like terms handler.
The specific conditions require the symbol to be undefined and the second
operand to the addition has to have no coefficient so it's likely a fairly
rare scenario. Still, it is somewhat surprising that nobody tripped on it
before now.
author | William Astle <lost@l-w.ca> |
---|---|
date | Mon, 23 Jan 2017 22:58:36 -0700 |
parents | 6153cb49403c |
children |
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/* lwexpr.h Copyright © 2010 William Astle This file is part of LWTOOLS. LWTOOLS 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/>. */ #ifndef ___lw_expr_h_seen___ #define ___lw_expr_h_seen___ #include <stdio.h> #ifdef _MSC_VER #include "lw_win.h" // windows build #endif enum { lw_expr_type_oper, // operator term lw_expr_type_int, // integer lw_expr_type_var, // a "variable" (string for the name) lw_expr_type_special // a "special" reference (user defined) }; enum { lw_expr_oper_plus = 1, // addition lw_expr_oper_minus, // subtraction lw_expr_oper_times, // multiplication lw_expr_oper_divide, // division lw_expr_oper_mod, // modulus lw_expr_oper_intdiv, // integer division lw_expr_oper_bwand, // bitwise and lw_expr_oper_bwor, // bitwise or lw_expr_oper_bwxor, // bitwise xor lw_expr_oper_and, // boolean and lw_expr_oper_or, // boolean or lw_expr_oper_neg, // unary negation, 2's complement lw_expr_oper_com, // unary 1's complement lw_expr_oper_com8, // 8 bit complement lw_expr_oper_none = 0 }; typedef struct lw_expr_priv * lw_expr_t; struct lw_expr_opers { lw_expr_t p; struct lw_expr_opers *next; }; struct lw_expr_priv { int type; // type of term int value; // integer value void *value2; // misc pointer value struct lw_expr_opers *operands; // ptr to list of operands (for operators) }; typedef lw_expr_t lw_expr_fn_t(int t, void *ptr, void *priv); typedef lw_expr_t lw_expr_fn2_t(char *var, void *priv); typedef lw_expr_t lw_expr_fn3_t(char **p, void *priv); typedef int lw_expr_testfn_t(lw_expr_t e, void *priv); lw_expr_t lwexpr_create(void); void lw_expr_destroy(lw_expr_t E); lw_expr_t lw_expr_copy(lw_expr_t E); void lw_expr_add_operand(lw_expr_t E, lw_expr_t O); lw_expr_t lw_expr_build(int exprtype, ...); char *lw_expr_print(lw_expr_t E); int lw_expr_compare(lw_expr_t E1, lw_expr_t E2); void lw_expr_simplify(lw_expr_t E, void *priv); void lw_expr_set_special_handler(lw_expr_fn_t *fn); void lw_expr_set_var_handler(lw_expr_fn2_t *fn); void lw_expr_set_term_parser(lw_expr_fn3_t *fn); lw_expr_t lw_expr_parse(char **p, void *priv); lw_expr_t lw_expr_parse_compact(char **p, void *priv); int lw_expr_istype(lw_expr_t e, int t); int lw_expr_intval(lw_expr_t e); int lw_expr_specint(lw_expr_t e); void *lw_expr_specptr(lw_expr_t e); int lw_expr_whichop(lw_expr_t e); int lw_expr_type(lw_expr_t e); int lw_expr_operandcount(lw_expr_t e); void lw_expr_setwidth(int w); // run a function on all terms in an expression; if the function // returns non-zero for any term, return non-zero, else return // zero int lw_expr_testterms(lw_expr_t e, lw_expr_testfn_t *fn, void *priv); void lw_expr_setdivzero(void (*fn)(void *priv)); #endif /* ___lw_expr_h_seen___ */