Add toString() overrides to internal solver members

packages/cassowary/lib/constraint.dart

@@ -24,4 +24,29 @@ class Constraint {
       required ? requiredPriority : p.clamp(0.0, requiredPriority - 1.0);
 
   Constraint operator |(double p) => this..priority = p;
+
+  String toString() {
+    StringBuffer buffer = new StringBuffer();
+    buffer.write(expression.toString());
+
+    switch (relation) {
+      case Relation.equalTo:
+        buffer.write(" <= 0 ");
+        break;
+      case Relation.greaterThanOrEqualTo:
+        buffer.write(" >= 0 ");
+        break;
+      case Relation.lessThanOrEqualTo:
+        buffer.write(" <= 0 ");
+        break;
+    }
+
+    buffer.write(" | priority = ${priority}");
+
+    if (required) {
+      buffer.write(" (required)");
+    }
+
+    return buffer.toString();
+  }
 }

packages/cassowary/lib/expression.dart

@@ -156,4 +156,17 @@ class Expression extends _EquationMember {
 
     return this._applyMultiplicand(1.0 / m.value);
   }
+
+  String toString() {
+    StringBuffer buffer = new StringBuffer();
+
+    terms.forEach((t) => buffer.write("${t}"));
+
+    if (constant != 0.0) {
+      buffer.write(constant.sign > 0.0 ? "+" : "-");
+      buffer.write(constant.abs());
+    }
+
+    return buffer.toString();
+  }
 }

packages/cassowary/lib/param.dart

@@ -14,5 +14,8 @@ class Param extends _EquationMember {
 
   double get value => variable.value;
 
+  String get name => variable.name;
+  set name(String name) => variable.name = name;
+
   Expression asExpression() => new Expression([new Term(variable, 1.0)], 0.0);
 }

packages/cassowary/lib/row.dart

@@ -61,4 +61,15 @@ class _Row {
     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();
+  }
 }

packages/cassowary/lib/solver.dart

@@ -550,6 +550,42 @@ class Solver {
 
     return _elvis(entering, new _Symbol(_SymbolType.invalid, 0));
   }
+
+  String toString() {
+    StringBuffer buffer = new StringBuffer();
+    String separator = "\n~~~~~~~~~";
+
+    // Objective
+    buffer.writeln(separator + " Objective");
+    buffer.writeln(_objective.toString());
+
+    // Tableau
+    buffer.writeln(separator + " Tableau");
+    _rows.forEach((symbol, row) {
+      buffer.write(symbol.toString());
+      buffer.write(" | ");
+      buffer.writeln(row.toString());
+    });
+
+    // Infeasible
+    buffer.writeln(separator + " Infeasible");
+    _infeasibleRows.forEach((symbol) => buffer.writeln(symbol.toString()));
+
+    // Variables
+    buffer.writeln(separator + " Variables");
+    _vars.forEach((variable, symbol) =>
+        buffer.writeln("${variable.toString()} = ${symbol.toString()}"));
+
+    // Edit Variables
+    buffer.writeln(separator + " Edit Variables");
+    _edits.forEach((variable, editinfo) => buffer.writeln(variable));
+
+    // Constraints
+    buffer.writeln(separator + " Constraints");
+    _constraints.forEach((constraint, _) => buffer.writeln(constraint));
+
+    return buffer.toString();
+  }
 }
 
 class _Tag {

packages/cassowary/lib/symbol.dart

@@ -11,4 +11,26 @@ class _Symbol {
   int tick;
 
   _Symbol(this.type, this.tick);
+
+  String toString() {
+    String typeString = "unknown";
+    switch (type) {
+      case _SymbolType.invalid:
+        typeString = "i";
+        break;
+      case _SymbolType.external:
+        typeString = "v";
+        break;
+      case _SymbolType.slack:
+        typeString = "s";
+        break;
+      case _SymbolType.error:
+        typeString = "e";
+        break;
+      case _SymbolType.dummy:
+        typeString = "d";
+        break;
+    }
+    return "${typeString}${tick}";
+  }
 }

packages/cassowary/lib/term.dart

@@ -16,4 +16,19 @@ class Term extends _EquationMember {
 
   Expression asExpression() =>
       new Expression([new Term(this.variable, this.coefficient)], 0.0);
+
+  String toString() {
+    StringBuffer buffer = new StringBuffer();
+
+    buffer.write(coefficient.sign > 0.0 ? "+" : "-");
+
+    if (coefficient.abs() != 1.0) {
+      buffer.write(coefficient.abs());
+      buffer.write("*");
+    }
+
+    buffer.write(variable);
+
+    return buffer.toString();
+  }
 }

packages/cassowary/lib/variable.dart

@@ -6,7 +6,16 @@ part of cassowary;
 
 class Variable {
   double value = 0.0;
-  Variable(this.value);
+  String name;
+
+  int _tick;
+  static int _total = 0;
+
+  Variable(this.value) : _tick = _total++;
 
   // TODO(csg): Add external variable update callbacks here
+
+  String get debugName => _elvis(name, "variable${_tick}");
+
+  String toString() => "${debugName}(=${value})";
 }