Fixed various parser bugs, implemented unary operators

app/imports/parser/parseTree/UnaryOperatorNode.js

@@ -0,0 +1,33 @@
+import ParseNode from '/imports/parser/parseTree/ParseNode.js';
+import ConstantNode from '/imports/parser/parseTree/ConstantNode.js';
+
+export default class UnaryOperatorNode extends ParseNode {
+  constructor({operator, right}) {
+		super(...arguments);
+    this.operator = operator;
+    this.right = right;
+  }
+  resolve(fn, scope, context){
+    let rightNode = this.right[fn](scope, context);
+    if (rightNode.type !== 'number'){
+      return new UnaryOperatorNode({
+        operator: this.operator,
+        right: rightNode,
+      });
+    }
+    let right = rightNode.value;
+    let result;
+    switch(this.operator){
+      case '-': result = -right; break;
+      case '+': result = +right; break;
+    }
+    return new ConstantNode({
+      value: result,
+      type: typeof result,
+    });
+  }
+  toString(){
+    let {right, operator} = this;
+    return `${operator}${right.toString()}`;
+  }
+}