141 lines
3.8 KiB
C++
141 lines
3.8 KiB
C++
// $Id$
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//
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// Cassowary Incremental Constraint Solver
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// Original Smalltalk Implementation by Alan Borning
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// This C++ Implementation by Greg J. Badros, <gjb@cs.washington.edu>
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// http://www.cs.washington.edu/homes/gjb
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// (C) 1998, 1999 Greg J. Badros and Alan Borning
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// See ../LICENSE for legal details regarding this software
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//
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// ClFDBinaryOneWayConstraint.cc
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#define CONFIG_H_INCLUDED
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#endif
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#include <cassowary/ClFDBinaryOneWayConstraint.h>
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#include <cassowary/ClLinearConstraint.h>
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#include <cassowary/ClTypedefs.h>
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#include <cassowary/ClLinearExpression.h>
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void
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ClFDBinaryOneWayConstraint::EnsurePreconditionsForCn(const ClConstraint &cn)
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{
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ClVarSet setRO = cn.ReadOnlyVars();
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if (setRO.size() > 1)
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throw ExCLTooDifficultSpecial("Only 0 or 1 read only variables are allowed");
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const ClLinearExpression &expr = cn.Expression();
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const ClVarToNumberMap &terms = expr.Terms();
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if (terms.size() > 2)
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throw ExCLTooDifficultSpecial("Cannot have more than 2 variables");
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if (terms.size() == 0)
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throw ExCLTooDifficultSpecial("Must have at least 1 variable");
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if (terms.size() == 2 && setRO.size() == 0)
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throw ExCLTooDifficultSpecial("Both variables cannot be read-write, one must be read-only");
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if (terms.size() == 1 && setRO.size() == 1)
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throw ExCLTooDifficultSpecial("Single read-only variable in LinearConstraint -- must not be read-only.");
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ClVariable clv = (*terms.begin()).first;
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/* GJB:FIXME:: iterate over all the variables */
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if (!clv->IsFDVariable()) {
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throw ExCLTooDifficultSpecial("FD constraint contains non-FD variables");
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}
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}
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bool
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ClFDBinaryOneWayConstraint::FCanConvertCn(const ClConstraint &cn)
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{
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try {
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EnsurePreconditionsForCn(cn);
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return true;
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} catch (...) {
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return false;
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}
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}
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ClFDBinaryOneWayConstraint::ClFDBinaryOneWayConstraint(const ClConstraint &cn)
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:ClFDConstraint(cn.strength(), cn.weight())
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{
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EnsurePreconditionsForCn(cn);
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list<FDNumber> l;
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/* GJB:FIXME:: varargs inteface, with sentinel as first arg? */
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l.push_back(9);
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l.push_back(10);
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l.push_back(12);
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l.push_back(14);
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l.push_back(20);
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ClVarSet setRO = cn.ReadOnlyVars();
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ClVariable clvRO = clvNil;
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ClVariable clvROLinear = clvNil;
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Number coeffRO = 0;
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ClVariable clvRW = clvNil;
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Number coeffRW = 0;
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if (setRO.size() == 1) {
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const ClVariable &clv = *(setRO.begin());
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if (clv->IsFDVariable())
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clvRO = clv;
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else
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clvRO = new ClFDVariable(clv.Name(),clv.IntValue(),l);
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clvROLinear = clv;
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}
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const ClLinearExpression &expr = cn.Expression();
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const ClVarToNumberMap &terms = expr.Terms();
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for (ClVarToNumberMap::const_iterator it = terms.begin();
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it != terms.end();
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++it) {
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ClVariable clv = (*it).first;
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if (clv == clvROLinear) {
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coeffRO = (*it).second;
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} else {
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if (clv->IsFDVariable())
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clvRW = clv;
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else
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clvRW = new ClFDVariable(clv.Name(),clv.Value(),l);
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coeffRW = (*it).second;
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}
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}
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assert(!clvRW.IsNil());
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if (coeffRW == 0) {
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throw ExCLTooDifficultSpecial("RW variable's coefficient must be non-zero");
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}
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bool fInequality = cn.IsInequality();
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bool fStrictInequality = cn.IsStrictInequality();
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double rhs_constant = expr.Constant();
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// now we have:
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// coeffRW * clvRW + coeffRO * clvRO <REL> rhs_constant
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// where <REL> is >= if fInequality, or = if !fInequality
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//
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// need:
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// clvRW <REL> coefficient * clvRO + constant
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//
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// so:
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// coefficient = -coeffRO/coeffRW
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// constant = rhs_constant/coeffRW
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if (fStrictInequality)
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_rel = cnGT;
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else if (fInequality)
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_rel = cnGEQ;
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else
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_rel = cnEQ;
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if (coeffRW < 0)
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_rel = ReverseInequality(_rel);
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_coefficient = -coeffRO/coeffRW;
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_constant = -rhs_constant/coeffRW;
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_vRW = clvRW;
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_vRO = clvRO;
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return;
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}
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