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