diff --git a/app/imports/api/engine/computation/utility/collate.js b/app/imports/api/engine/computation/utility/collate.js
new file mode 100644
index 00000000..d6599d65
--- /dev/null
+++ b/app/imports/api/engine/computation/utility/collate.js
@@ -0,0 +1,12 @@
+// Collate the array with the given value or array of values, creating the
+// array if it doesn't exist
+export default function collate(array, toAdd){
+  if (Array.isArray(toAdd) && toAdd.length){
+    if (!array) array = [];
+    array.push(...toAdd);
+  } else if (toAdd) {
+    if (!array) array = [];
+    array.push(toAdd);
+  }
+  return array;
+}
diff --git a/app/imports/parser/ResolveContext.js b/app/imports/parser/ResolveContext.js
new file mode 100644
index 00000000..3edd2fa8
--- /dev/null
+++ b/app/imports/parser/ResolveContext.js
@@ -0,0 +1,20 @@
+export default class Context {
+  constructor({errors = [], rolls = []}){
+    this.errors = errors;
+    this.rolls = rolls;
+  }
+  error(e){
+    if (!e) return;
+    if (typeof e === 'string'){
+      this.errors.push({
+        type: 'error',
+        message: e,
+      });
+    } else {
+      this.errors.push(e);
+    }
+  }
+  roll(r){
+    this.rolls.push(r);
+  }
+}
diff --git a/app/imports/parser/compute.js b/app/imports/parser/compute.js
deleted file mode 100644
index 5386218b..00000000
--- a/app/imports/parser/compute.js
+++ /dev/null
@@ -1 +0,0 @@
-// Takes a parse tree and computes it down as far as possible into a real number
diff --git a/app/imports/parser/parseTree/AccessorNode.js b/app/imports/parser/parseTree/AccessorNode.js
deleted file mode 100644
index ad2d7cad..00000000
--- a/app/imports/parser/parseTree/AccessorNode.js
+++ /dev/null
@@ -1,54 +0,0 @@
-import ParseNode from '/imports/parser/parseTree/ParseNode.js';
-import ConstantNode from '/imports/parser/parseTree/ConstantNode.js';
-
-export default class AccessorNode extends ParseNode {
-  constructor({name, path}) {
-    super(...arguments);
-    this.name = name;
-    this.path = path;
-  }
-  compile(scope, context){
-    let value = scope && scope[this.name];
-    // For objects, get their value
-    this.path.forEach(name => {
-      if (value === undefined) return;
-      value = value[name];
-    });
-    let type = typeof value;
-    if (type === 'string' || type === 'number' || type === 'boolean'){
-      return new ConstantNode({value, type});
-    } else if (type === 'undefined'){
-      return new AccessorNode({
-        name: this.name,
-        path: this.path,
-      });
-    } else {
-      if (context) context.storeError({
-        type: 'error',
-        message: `${this.name} returned an unexpected type`
-      });
-      return new AccessorNode({
-        name: this.name,
-        path: this.path,
-      });
-    }
-  }
-  reduce(scope, context){
-    let result = this.compile(scope, context);
-    if (result instanceof AccessorNode){
-      if (context) context.storeError({
-        type: 'info',
-        message: `${result.toString()} not found, set to 0`
-      });
-      return new ConstantNode({
-        type: 'number',
-        value: 0,
-      });
-    } else {
-      return result;
-    }
-  }
-  toString(){
-    return `${this.name}.${this.path.join('.')}`;
-  }
-}
diff --git a/app/imports/parser/parseTree/ArrayNode.js b/app/imports/parser/parseTree/ArrayNode.js
deleted file mode 100644
index 2f31fa69..00000000
--- a/app/imports/parser/parseTree/ArrayNode.js
+++ /dev/null
@@ -1,39 +0,0 @@
-import ParseNode from '/imports/parser/parseTree/ParseNode.js';
-import ConstantNode from '/imports/parser/parseTree/ConstantNode.js';
-
-export default class ArrayNode extends ParseNode {
-  constructor({values}) {
-    super(...arguments);
-    this.values = values;
-  }
-  static fromConstantArray(array){
-    let values = array.map( value => {
-      let type = typeof value;
-      if (
-        type === 'string' ||
-        type === 'number' ||
-        type === 'boolean' ||
-        type === 'undefined'
-      ){
-        return new ConstantNode({value, type});
-      } else {
-        throw `Unexpected type in constant array: ${type}`
-      }
-    });
-    return new ArrayNode({values});
-  }
-  resolve(fn, scope, context){
-    let values = this.values.map(node => node[fn](scope, context));
-    return new ArrayNode({values});
-  }
-  toString(){
-    return `[${this.values.map(node => node.toString()).join(', ')}]`;
-  }
-  traverse(fn){
-    fn(this);
-    this.values.forEach(value => value.traverse(fn));
-  }
-  replaceChildren(fn){
-    this.values = this.values.map(node => node.replaceNodes(fn));
-  }
-}
diff --git a/app/imports/parser/parseTree/CallNode.js b/app/imports/parser/parseTree/CallNode.js
deleted file mode 100644
index 59c9e9ff..00000000
--- a/app/imports/parser/parseTree/CallNode.js
+++ /dev/null
@@ -1,126 +0,0 @@
-import ParseNode from '/imports/parser/parseTree/ParseNode.js';
-import ErrorNode from '/imports/parser/parseTree/ErrorNode.js';
-import ConstantNode from '/imports/parser/parseTree/ConstantNode.js';
-import functions from '/imports/parser/functions.js';
-
-export default class CallNode extends ParseNode {
-  constructor({functionName, args}) {
-    super(...arguments);
-    this.functionName = functionName;
-    this.args = args;
-  }
-  resolve(fn, scope, context){
-    let func = functions[this.functionName];
-    // Check that the function exists
-    if (!func) return new ErrorNode({
-      node: this,
-      error: `${this.functionName} is not a supported function`,
-      context,
-    });
-
-    // Resolve the arguments
-    let resolvedArgs = this.args.map(node => node[fn](scope, context));
-    // Check that the arguments match what is expected
-    let checkFailed = this.checkArugments({
-      fn,
-      context,
-      resolvedArgs,
-      argumentsExpected: func.arguments
-    });
-
-    if (checkFailed){
-      if (fn === 'reduce'){
-        return new ErrorNode({
-          node: this,
-          error: `Invalid arguments to ${this.functionName} function`,
-        });
-      } else {
-        return new CallNode({
-          functionName: this.functionName,
-          args: resolvedArgs,
-        });
-      }
-    }
-
-    // Map contant nodes to constants before attempting to run the function
-    let mappedArgs = resolvedArgs.map(node => {
-      if (node instanceof ConstantNode){
-        return node.value;
-      } else {
-        return node;
-      }
-    });
-
-    try {
-      // Run the function
-      let value = func.fn.apply(null, mappedArgs);
-
-      let type = typeof value;
-      if (type === 'number' || type === 'string' || type === 'boolean'){
-        // Convert constant results into constant nodes
-        return new ConstantNode({ value, type });
-      } else {
-        return value;
-      }
-    } catch (error) {
-      return new ErrorNode({
-        node: this,
-        error: error.message || error,
-        context,
-      });
-    }
-  }
-  toString(){
-    return `${this.functionName}(${this.args.map(node => node.toString()).join(', ')})`;
-  }
-  traverse(fn){
-    fn(this);
-    this.args.forEach(arg => arg.traverse(fn));
-  }
-  replaceChildren(fn){
-    this.args = this.args.map(arg => arg.replaceNodes(fn));
-  }
-  checkArugments({fn, context, argumentsExpected, resolvedArgs}){
-    // Check that the number of arguments matches the number expected
-    if (
-      !argumentsExpected.anyLength &&
-      argumentsExpected.length !== resolvedArgs.length
-    ){
-      context.storeError({
-        type: 'error',
-        message: 'Incorrect number of arguments ' +
-          `to ${this.functionName} function, ` +
-          `expected ${argumentsExpected.length} got ${resolvedArgs.length}`
-        });
-      return true;
-    }
-
-    let failed = false;
-    // Check that each argument is of the correct type
-    resolvedArgs.forEach((node, index) => {
-      let type;
-      if (argumentsExpected.anyLength){
-        type = argumentsExpected[0];
-      } else {
-        type = argumentsExpected[index];
-      }
-      if (typeof type === 'string'){
-        // Type being a string means a constant node with matching type
-        if (node.type !== type) failed = true;
-      } else {
-        // Otherwise check that the node is an instance of the given type
-        if (!(node instanceof type)) failed = true;
-      }
-      if (failed && fn === 'reduce'){
-        let typeName = typeof type === 'string' ? type : type.constructor.name;
-        let nodeName = node.type || node.constructor.name
-        context.storeError({
-          type: 'error',
-          message: `Incorrect arguments to ${this.functionName} function` +
-          `expected ${typeName} got ${nodeName}`
-        });
-      }
-    });
-    return failed;
-  }
-}
diff --git a/app/imports/parser/parseTree/ConstantNode.js b/app/imports/parser/parseTree/ConstantNode.js
deleted file mode 100644
index 708bfaba..00000000
--- a/app/imports/parser/parseTree/ConstantNode.js
+++ /dev/null
@@ -1,22 +0,0 @@
-import ParseNode from '/imports/parser/parseTree/ParseNode.js';
-
-export default class ConstantNode extends ParseNode {
-  constructor({value, type}){
-		super(...arguments);
-    // string, number, boolean, uncompiledNode
-    this.type = type;
-    this.value = value;
-  }
-  compile(){
-    return this;
-  }
-  toString(){
-    return `${this.value}`;
-  }
-  get isNumber(){
-    return this.type === 'number';
-  }
-  get isInteger(){
-    return this.type === 'number' && Number.isInteger(this.value);
-  }
-}
diff --git a/app/imports/parser/parseTree/ErrorNode.js b/app/imports/parser/parseTree/ErrorNode.js
deleted file mode 100644
index ff9565ee..00000000
--- a/app/imports/parser/parseTree/ErrorNode.js
+++ /dev/null
@@ -1,21 +0,0 @@
-import ParseNode from '/imports/parser/parseTree/ParseNode.js';
-
-export default class ErrorNode extends ParseNode {
-  constructor({node, error, context}) {
-		super(...arguments);
-    this.node = node;
-    this.error = error;
-    if (context){
-      context.storeError({
-        type: 'error',
-        message: error,
-      });
-    }
-  }
-  compile(){
-    return this;
-  }
-  toString(){
-    return this.error.toString();
-  }
-}
diff --git a/app/imports/parser/parseTree/IfNode.js b/app/imports/parser/parseTree/IfNode.js
deleted file mode 100644
index a94f21c2..00000000
--- a/app/imports/parser/parseTree/IfNode.js
+++ /dev/null
@@ -1,42 +0,0 @@
-import ParseNode from '/imports/parser/parseTree/ParseNode.js';
-import ConstantNode from '/imports/parser/parseTree/ConstantNode.js';
-
-export default class IfNode extends ParseNode {
-  constructor({condition, consequent, alternative}){
-		super(...arguments);
-    this.condition = condition;
-    this.consequent = consequent;
-    this.alternative = alternative;
-  }
-  toString(){
-    let {condition, consequent, alternative} = this;
-    return `${condition.toString()} ? ${consequent.toString()} : ${alternative.toString()}`
-  }
-  resolve(fn, scope, context){
-    let condition = this.condition[fn](scope, context);
-    if (condition instanceof ConstantNode){
-      if (condition.value){
-        return this.consequent[fn](scope, context);
-      } else {
-        return this.alternative[fn](scope, context);
-      }
-    } else {
-      return new IfNode({
-        condition: condition,
-        consequent: this.consequent,
-        alternative: this.alternative,
-      });
-    }
-  }
-  traverse(fn){
-    fn(this);
-    this.condition.traverse(fn);
-    this.consequent.traverse(fn);
-    this.alternative.traverse(fn);
-  }
-  replaceChildren(fn){
-    this.condition = this.condition.replaceNodes(fn);
-    this.consequent = this.consequent.replaceNodes(fn);
-    this.alternative = this.alternative.replaceNodes(fn);
-  }
-}
diff --git a/app/imports/parser/parseTree/_index.js b/app/imports/parser/parseTree/_index.js
new file mode 100644
index 00000000..571f7e7a
--- /dev/null
+++ b/app/imports/parser/parseTree/_index.js
@@ -0,0 +1,5 @@
+import accessor from './accessor.js';
+
+export default Object.freeze({
+  accessor,
+});
diff --git a/app/imports/parser/parseTree/accessor.js b/app/imports/parser/parseTree/accessor.js
new file mode 100644
index 00000000..5ebbf246
--- /dev/null
+++ b/app/imports/parser/parseTree/accessor.js
@@ -0,0 +1,66 @@
+import constant from './constant.js';
+
+const accessor = {
+  create({name, path}) {
+    return {
+      type: 'accessor',
+      path,
+      name,
+    };
+  },
+  compile(node, scope, context){
+    let value = scope && scope[node.name];
+    // For objects, get their value
+    node.path.forEach(name => {
+      if (value === undefined) return;
+      value = value[name];
+    });
+    let valueType = typeof value;
+    if (valueType === 'string' || valueType === 'number' || valueType === 'boolean'){
+      return {
+        result: constant.create({
+          value,
+          valueType
+        }),
+        context,
+      };
+    } else if (valueType === 'undefined'){
+      return {
+        result: accessor.create({
+          name: node.name,
+          path: node.path,
+        }),
+        context,
+      };
+    } else {
+      context.error(`${node.name} returned an unexpected type`);
+      return {
+        result: accessor.create({
+          name: node.name,
+          path: node.path,
+        }),
+        context,
+      };
+    }
+  },
+  reduce(node, scope, context){
+    let { result } = accessor.compile(node, scope, context);
+    if (result.type === 'accessor'){
+      context.error(`${accessor.toString(result)} not found, set to 0`);
+      return {
+        result: constant.create({
+          value: 0,
+          valueType: 'number',
+        }),
+        context
+      };
+    } else {
+      return {result, context};
+    }
+  },
+  toString(node){
+    return `${node.name}.${node.path.join('.')}`;
+  }
+}
+
+export default accessor;
diff --git a/app/imports/parser/parseTree/array.js b/app/imports/parser/parseTree/array.js
new file mode 100644
index 00000000..407ab92a
--- /dev/null
+++ b/app/imports/parser/parseTree/array.js
@@ -0,0 +1,46 @@
+import constant from './constant.js';
+import resolve, { toString, traverse } from '../resolve.js';
+
+const array = {
+  create({values}) {
+    return {
+      type: 'array',
+      values,
+    };
+  },
+  fromConstantArray(array){
+    let values = array.map( value => {
+      let valueType = typeof value;
+      if (
+        valueType === 'string' ||
+        valueType === 'number' ||
+        valueType === 'boolean' ||
+        valueType === 'undefined'
+      ){
+        return constant.create({value, valueType});
+      } else {
+        throw `Unexpected type in constant array: ${valueType}`
+      }
+    });
+    return array.create({values});
+  },
+  resolve(fn, node, scope){
+    let values = node.values.map(node => {
+      let { result } = resolve(fn, node, scope, context);
+      return result;
+    });
+    return {
+      result: array.create({values}),
+      context,
+    };
+  },
+  toString(node){
+    return `[${node.values.map(value => toString(value)).join(', ')}]`;
+  },
+  traverse(node, fn){
+    fn(node);
+    node.values.forEach(value => traverse(value, fn));
+  },
+}
+
+export default array;
diff --git a/app/imports/parser/parseTree/call.js b/app/imports/parser/parseTree/call.js
new file mode 100644
index 00000000..6893dbf4
--- /dev/null
+++ b/app/imports/parser/parseTree/call.js
@@ -0,0 +1,146 @@
+import error from './error.js';
+import constant from './constant.js';
+import functions from '/imports/parser/functions.js';
+import resolve, { toString, traverse, mergeResolvedNodes } from '../resolve.js';
+
+const call = {
+  create({functionName, args}) {
+    return {
+      type: 'call',
+      functionName,
+      args,
+    }
+  },
+  resolve(fn, node, scope, context){
+    let func = functions[node.functionName];
+    // Check that the function exists
+    if (!func) {
+      context.error(`${node.functionName} is not a supported function`);
+      return {
+        result: error.create({
+          node: node,
+          error: `${node.functionName} is not a supported function`,
+        }),
+        context,
+      };
+    }
+
+    // Resolve the arguments
+    let resolvedArgs = node.args.map(arg => {
+      let { result } = resolve(fn, arg, scope, context);
+      return result;
+    });
+
+    // Check that the arguments match what is expected
+    let checkFailed = call.checkArugments({
+      fn,
+      resolvedArgs,
+      argumentsExpected: func.arguments,
+      context,
+    });
+
+    if (checkFailed){
+      if (fn === 'reduce'){
+        context.error(`Invalid arguments to ${node.functionName} function`);
+        return {
+          result: error.create({
+            node: node,
+            error: `Invalid arguments to ${node.functionName} function`,
+          }),
+          context,
+        };
+      } else {
+        return {
+          result: call.create({
+            functionName: node.functionName,
+            args: resolvedArgs,
+          }),
+          context,
+        };
+      }
+    }
+
+    // Map contant nodes to constants before attempting to run the function
+    let mappedArgs = resolvedArgs.map(arg => {
+      if (arg.type === 'constant'){
+        return arg.value;
+      } else {
+        return arg;
+      }
+    });
+
+    try {
+      // Run the function
+      let value = func.fn.apply(null, mappedArgs);
+
+      let valueType = typeof value;
+      if (valueType === 'number' || valueType === 'string' || valueType === 'boolean'){
+        // Convert constant results into constant nodes
+        return {
+          result: constant.create({ value, valueType }),
+          context,
+        };
+      } else {
+        return {
+          result: value,
+          context,
+        };
+      }
+    } catch (error) {
+      context.error(error.message || error);
+      return {
+        result: error.create({
+          node: node,
+          error: error.message || error,
+        }),
+        context,
+      }
+    }
+  },
+  toString(node){
+    return `${node.functionName}(${node.args.map(arg => toString(arg)).join(', ')})`;
+  },
+  traverse(node, fn){
+    fn(node);
+    node.args.forEach(arg => traverse(arg, fn));
+  },
+  checkArugments({node, fn, argumentsExpected, resolvedArgs, context}){
+    // Check that the number of arguments matches the number expected
+    if (
+      !argumentsExpected.anyLength &&
+      argumentsExpected.length !== resolvedArgs.length
+    ){
+      context.error('Incorrect number of arguments ' +
+        `to ${node.functionName} function, ` +
+        `expected ${argumentsExpected.length} got ${resolvedArgs.length}`);
+      return true;
+    }
+
+    let failed = false;
+    // Check that each argument is of the correct type
+    resolvedArgs.forEach((node, index) => {
+      let type;
+      if (argumentsExpected.anyLength){
+        type = argumentsExpected[0];
+      } else {
+        type = argumentsExpected[index];
+      }
+      if (typeof type === 'string'){
+        // Type being a string means a constant node with matching type
+        if (node.valueType !== type) failed = true;
+      } else {
+        // Otherwise check that the node is an instance of the given type
+        if (!(node instanceof type)) failed = true;
+      }
+      if (failed && fn === 'reduce'){
+        let typeName = typeof type === 'string' ? type : type.constructor.name;
+        let nodeName = node.type;
+        context.error(`Incorrect arguments to ${node.functionName} function` +
+          `expected ${typeName} got ${nodeName}`);
+      }
+    });
+    return failed;
+  }
+}
+
+export default call;
diff --git a/app/imports/parser/parseTree/constant.js b/app/imports/parser/parseTree/constant.js
new file mode 100644
index 00000000..4220bc96
--- /dev/null
+++ b/app/imports/parser/parseTree/constant.js
@@ -0,0 +1,18 @@
+const constant = {
+  create({value, valueType}){
+    if (!valueType) throw `Expected valueType to be set, got ${valueType}`
+    return {
+      type: 'constant',
+      valueType,
+      value,
+    }
+  },
+  compile(node){
+    return node;
+  },
+  toString(node){
+    return `${node.value}`;
+  },
+}
+
+export default constant;
diff --git a/app/imports/parser/parseTree/error.js b/app/imports/parser/parseTree/error.js
new file mode 100644
index 00000000..8533061b
--- /dev/null
+++ b/app/imports/parser/parseTree/error.js
@@ -0,0 +1,17 @@
+const error = {
+  create({node, error}) {
+    return {
+      type: 'error',
+      node,
+      error,
+    }
+  },
+  compile(node){
+    return node;
+  },
+  toString(node){
+    return node.error.toString();
+  },
+}
+
+export default error;
diff --git a/app/imports/parser/parseTree/if.js b/app/imports/parser/parseTree/if.js
new file mode 100644
index 00000000..369ff924
--- /dev/null
+++ b/app/imports/parser/parseTree/if.js
@@ -0,0 +1,59 @@
+import resolve, {traverse, toString, mergeResolvedNodes} from '../resolve';
+import collate from '/imports/api/engine/computation/utility/collate.js';
+
+const ifNode = {
+  create({condition, consequent, alternative}){
+    return {
+      type: 'if',
+      condition,
+      consequent,
+      alternative,
+    };
+  },
+  toString(node){
+    let {condition, consequent, alternative} = node;
+    return `${toString(condition)} ? ${toString(consequent)} : ${toString(alternative)}`
+  },
+  resolve(fn, node, scope){
+    let rest, condition, consequent, alternative;
+    let resolved = {};
+
+    ({result: condition, ...rest} = resolve(fn, node.condition, scope));
+    mergeResolvedNodes(resolved, rest);
+
+    if (condition.type === 'constant'){
+      if (condition.value){
+        ({result: consequent, ...rest} = resolve(fn, node.consequent, scope));
+        mergeResolvedNodes(resolved, rest);
+        return {
+          result: consequent,
+          ...resolved
+        };
+      } else {
+        ({result: alternative, ...rest} = resolve(fn, node.alternative, scope));
+        mergeResolvedNodes(resolved, rest);
+        return {
+          result: alternative,
+          ...resolved
+        };
+      }
+    } else {
+      return {
+        result: ifNode.create({
+          condition: condition,
+          consequent: node.consequent,
+          alternative: node.alternative,
+        }),
+        ...resolved
+      };
+    }
+  },
+  traverse(node, fn){
+    fn(node);
+    traverse(node.condition, fn);
+    traverse(node.consequent, fn);
+    traverse(node.alternative, fn);
+  },
+}
+
+export default ifNode;
diff --git a/app/imports/parser/parseTree/index.js b/app/imports/parser/parseTree/index.js
new file mode 100644
index 00000000..dcb19e2d
--- /dev/null
+++ b/app/imports/parser/parseTree/index.js
@@ -0,0 +1,76 @@
+import resolve, {traverse, toString, mergeResolvedNodes} from '../resolve';
+
+const index = {
+  create({array, index}) {
+		return {
+      type: 'index',
+      array,
+      index,
+    }
+  },
+  resolve(fn, node, scope){
+    let index, array, rest;
+    let resolved = {};
+    ({result: index, ...rest} = resolve(fn, node.index, scope));
+    mergeResolvedNodes(resolved, rest);
+    ({result: array, ...rest} = resolve(fn, node.array, scope));
+    mergeResolvedNodes(resolved, rest);
+
+    if (
+      index.valueType === 'number' &&
+      Number.isInteger(index.value) &&
+      array.type === 'array'
+    ){
+      if (index.value < 1 || index.value > array.values.length){
+        mergeResolvedNodes(resolved, {
+          errors: [{
+            type: 'warning',
+            message: `Index of ${index.value} is out of range for an array` +
+              ` of length ${array.values.length}`,
+          }]
+        });
+      }
+      let selection = array.values[index.value - 1];
+      if (selection){
+        let result;
+        ({result, ...rest} = resolve(fn, selection, scope));
+        mergeResolvedNodes(resolved, rest)
+        return result;
+      }
+    } else if (fn === 'reduce'){
+      if (!(array instanceof ArrayNode)){
+        return new ErrorNode({
+          node: node,
+          error: 'Can not get the index of a non-array node: ' +
+            node.array.toString() + ' = ' + array.toString(),
+          context,
+        });
+      } else if (!index.isInteger){
+        return new ErrorNode({
+          node: node,
+          error: array.toString() + ' is not an integer index of the array',
+          context,
+        });
+      }
+    }
+    return new IndexNode({
+      index,
+      array,
+      previousNodes: [node],
+    });
+  },
+  toString(){
+    return `${node.array.toString()}[${node.index.toString()}]`;
+  },
+  traverse(fn){
+    fn(node);
+    node.array.traverse(fn);
+    node.index.traverse(fn);
+  },
+  replaceChildren(fn){
+    node.array = node.array.replaceNodes(fn);
+    node.index = node.index.replaceNodes(fn);
+  }
+}
+
+export default index;
diff --git a/app/imports/parser/parser.test.js b/app/imports/parser/parser.test.js
new file mode 100644
index 00000000..30f0b0b9
--- /dev/null
+++ b/app/imports/parser/parser.test.js
@@ -0,0 +1,11 @@
+import { parse } from './parser';
+import { assert } from 'chai';
+
+describe('Parser', function(){
+  it('parses valid text without error', function(){
+    assert.typeOf(parse('1'), 'object');
+  });
+  it('parses various operations', function(){
+    assert.typeOf(parse('1 + 2 * 3 / 4 * 1d8'), 'object');
+  });
+});
diff --git a/app/imports/parser/resolve.js b/app/imports/parser/resolve.js
new file mode 100644
index 00000000..86d2fad6
--- /dev/null
+++ b/app/imports/parser/resolve.js
@@ -0,0 +1,45 @@
+import nodeTypeIndex from './parseTree/index.js';
+import collate from '/imports/api/engine/computation/utility/collate.js';
+import Context from './ResolveContext.js';
+
+// Takes a parse ndoe and computes it to a set detail level
+// returns {result, context}
+export default function resolve(fn, node, scope, context = new Context()){
+  let type = nodeTypeIndex[node.type];
+  if (!type){
+    throw new Meteor.Error(`Parse node type: ${node.type} not implemented`);
+  }
+  if (type.resolve){
+    return type.resolve(fn, node, scope, context);
+  } else if (type[fn]) {
+    return type[fn](node, scope, context);
+  } else if (fn === 'reduce' && type.roll) {
+    return type.roll(node, scope, context)
+  } else if (type.compile){
+    return type.compile(node, scope, context)
+  } else {
+    throw new Meteor.Error('Compile not implemented on ' + node.type);
+  }
+}
+
+export function toString(node){
+  let type = nodeTypeIndex[node.type];
+  if (!type.toString){
+    throw new Meteor.Error('toString not implemented on ' + node.type);
+  }
+  return type.toString(node);
+}
+
+export function traverse(node, fn){
+  let type = nodeTypeIndex[node.type];
+  if (type.traverse){
+    return type.traverse(node, fn);
+  }
+  return fn(node);
+}
+
+export function mergeResolvedNodes(main, other){
+  main.errors = collate(main.errors, other.errors);
+  main.rolls = collate(main.rolls, other.rolls);
+  return main;
+}