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