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// Copyright (c) 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
part of cassowary;
class _Row {
final Map<_Symbol, double> cells;
double constant = 0.0;
_Row(this.constant) : this.cells = new Map<_Symbol, double>();
_Row.fromRow(_Row row)
: this.cells = new Map<_Symbol, double>.from(row.cells),
this.constant = row.constant;
double add(double value) => constant += value;
void insertSymbol(_Symbol symbol, [double coefficient = 1.0]) {
double val = _elvis(cells[symbol], 0.0);
if (_nearZero(val + coefficient)) {
cells.remove(symbol);
} else {
cells[symbol] = val + coefficient;
}
}
void insertRow(_Row other, [double coefficient = 1.0]) {
constant += other.constant * coefficient;
other.cells.forEach((s, v) => insertSymbol(s, v * coefficient));
}
void removeSymbol(_Symbol symbol) {
cells.remove(symbol);
}
void reverseSign() {
constant = -constant;
cells.forEach((s, v) => cells[s] = -v);
}
void solveForSymbol(_Symbol symbol) {
assert(cells.containsKey(symbol));
double coefficient = -1.0 / cells[symbol];
cells.remove(symbol);
constant *= coefficient;
cells.forEach((s, v) => cells[s] = v * coefficient);
}
void solveForSymbols(_Symbol lhs, _Symbol rhs) {
insertSymbol(lhs, -1.0);
solveForSymbol(rhs);
}
double coefficientForSymbol(_Symbol symbol) => _elvis(cells[symbol], 0.0);
void substitute(_Symbol symbol, _Row row) {
double coefficient = cells[symbol];
if (coefficient == null) {
return;
}
cells.remove(symbol);
insertRow(row, coefficient);
}
String toString() {
StringBuffer buffer = new StringBuffer();
buffer.write(constant);
cells.forEach((symbol, value) =>
buffer.write(" + " + value.toString() + " * " + symbol.toString()));
return buffer.toString();
}
}