diff --git a/app/imports/parser/grammar.js b/app/imports/parser/grammar.js
index c158d3ea..310a2ad8 100644
--- a/app/imports/parser/grammar.js
+++ b/app/imports/parser/grammar.js
@@ -79,7 +79,7 @@ let ParserRules = [
     {"name": "exponentExpression", "symbols": ["callExpression", "_", (lexer.has("exponentOperator") ? {type: "exponentOperator"} : exponentOperator), "_", "exponentExpression"], "postprocess": d => operator(d, 'exponent')},
     {"name": "exponentExpression", "symbols": ["callExpression"], "postprocess": id},
     {"name": "callExpression", "symbols": ["name", "_", "arguments"], "postprocess": 
-        d => new CallNode ({type: "call", fn: d[0], arguments: d[2]})
+        d => new CallNode ({functionName: d[0].name, args: d[2]})
           },
     {"name": "callExpression", "symbols": ["indexExpression"], "postprocess": id},
     {"name": "arguments$ebnf$1$subexpression$1", "symbols": ["expression"], "postprocess": d => d[0]},
diff --git a/app/imports/parser/grammar.ne b/app/imports/parser/grammar.ne
index 3f6c7fc6..4e199c11 100644
--- a/app/imports/parser/grammar.ne
+++ b/app/imports/parser/grammar.ne
@@ -103,7 +103,7 @@ exponentExpression ->
 
 callExpression ->
   name _ arguments {%
-    d => new CallNode ({type: "call", fn: d[0], arguments: d[2]})
+    d => new CallNode ({functionName: d[0].name, args: d[2]})
   %}
 | indexExpression {% id %}
 
diff --git a/app/imports/parser/parseTree/ArrayNode.js b/app/imports/parser/parseTree/ArrayNode.js
index 43f592ad..b74fc455 100644
--- a/app/imports/parser/parseTree/ArrayNode.js
+++ b/app/imports/parser/parseTree/ArrayNode.js
@@ -2,12 +2,12 @@ import ParseNode from '/imports/parser/parseTree/ParseNode.js';
 
 export default class ArrayNode extends ParseNode {
   constructor({values}) {
-		super();
+    super(...arguments);
     this.values = values;
   }
-  compile(){
-    let values = this.values.map(node => node.compile());
-    return new ArrayNode({values});
+  compile(scope){
+    let values = this.values.map(node => node.compile(scope));
+    return new ArrayNode({values, previousNodes: [this]});
   }
   toString(){
     return `[${this.values.map(node => node.toString()).join(', ')}]`;
diff --git a/app/imports/parser/parseTree/CallNode.js b/app/imports/parser/parseTree/CallNode.js
index 8ad1dfb5..52ab227c 100644
--- a/app/imports/parser/parseTree/CallNode.js
+++ b/app/imports/parser/parseTree/CallNode.js
@@ -1 +1,82 @@
-//TODO
+import ParseNode from '/imports/parser/parseTree/ParseNode.js';
+import ErrorNode from '/imports/parser/parseTree/ErrorNode.js';
+import ConstantNode from '/imports/parser/parseTree/ConstantNode.js';
+
+export default class CallNode extends ParseNode {
+  constructor({functionName, args}) {
+    super(...arguments);
+    this.functionName = functionName;
+    this.args = args;
+  }
+  compile(scope){
+    return this.resolve('compile', scope);
+  }
+  roll(scope){
+    return this.resolve('roll', scope);
+  }
+  reduce(scope){
+    return this.resolve('reduce', scope);
+  }
+  resolve(fn, scope){
+    let func = functions[this.functionName];
+    if (!func) return new ErrorNode({
+      node: this,
+      error: `${this.functionName} is not a function`,
+      previousNodes: [this],
+    });
+    let args = castArgsToType({fn, scope, args: this.args, type: func.argumentType});
+    if (args.failed){
+      if (fn === 'reduce'){
+        return new ErrorNode({
+          node: this,
+          error: 'Could not convert all arguments to the correct type',
+          previousNodes: [this],
+        });
+      } else {
+        return new CallNode({
+          functionName: this.functionName,
+          args: args,
+          previousNodes: [this],
+        });
+      }
+    } else {
+      let value = func.fn.apply(null, args);
+      console.log({args})
+      return new ConstantNode({
+        value,
+        type: 'number',
+        previousNodes: [this],
+      });
+    }
+
+  }
+  toString(){
+    return `${this.functionName}(${this.args.map(node => node.toString()).join(', ')})`;
+  }
+}
+
+const functions = {
+  'min': {
+    comment: 'Returns the lowest of the given numbers',
+    argumentType: 'number',
+    resultType: 'number',
+    fn: Math.min,
+  },
+}
+
+function castArgsToType({fn, scope, args, type}){
+  let resolvedArgs = args.map(node => node[fn](scope))
+  let result = [];
+  if (type === 'number'){
+    resolvedArgs.forEach(node => {
+      if (node.isNumber){
+        result.push(node.value);
+      } else {
+        resolvedArgs.failed = true;
+      }
+    })
+  }
+  if (resolvedArgs.failed) return resolvedArgs;
+  console.log({result})
+  return result;
+}
diff --git a/app/imports/parser/parseTree/ConstantNode.js b/app/imports/parser/parseTree/ConstantNode.js
index 4d3198fd..268011eb 100644
--- a/app/imports/parser/parseTree/ConstantNode.js
+++ b/app/imports/parser/parseTree/ConstantNode.js
@@ -1,12 +1,12 @@
 import ParseNode from '/imports/parser/parseTree/ParseNode.js';
 
 export default class ConstantNode extends ParseNode {
-  constructor({value, type, errors}){
-		super();
+  constructor({value, type, rollTable}){
+		super(...arguments);
     // string, number, boolean, numberArray, uncompiledNode
     this.type = type;
     this.value = value;
-    if (errors) this.errors = errors;
+    if (rollTable) this.rollTable = rollTable;
   }
   compile(){
     return this;
@@ -18,6 +18,6 @@ export default class ConstantNode extends ParseNode {
     return this.type === 'number';
   }
   get isInteger(){
-    return this.isNumberNode && Number.isInteger(this.value);
+    return this.type === 'number' && Number.isInteger(this.value);
   }
 }
diff --git a/app/imports/parser/parseTree/ErrorNode.js b/app/imports/parser/parseTree/ErrorNode.js
index bbef94c3..44fe2434 100644
--- a/app/imports/parser/parseTree/ErrorNode.js
+++ b/app/imports/parser/parseTree/ErrorNode.js
@@ -2,7 +2,7 @@ import ParseNode from '/imports/parser/parseTree/ParseNode.js';
 
 export default class ErrorNode extends ParseNode {
   constructor({node, error}) {
-		super();
+		super(...arguments);
     this.node = node;
     this.error = error;
   }
diff --git a/app/imports/parser/parseTree/IfNode.js b/app/imports/parser/parseTree/IfNode.js
index a801e4bd..66334d84 100644
--- a/app/imports/parser/parseTree/IfNode.js
+++ b/app/imports/parser/parseTree/IfNode.js
@@ -1,9 +1,8 @@
 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();
+		super(...arguments);
     this.condition = condition;
     this.consequent = consequent;
     this.alternative = alternative;
@@ -12,33 +11,26 @@ export default class IfNode extends ParseNode {
     let {condition, consequent, alternative} = this;
     return `${condition.toString()} ? ${consequent.toString()} : ${alternative.toString()}`
   }
-  compile(){
-    let condition = this.condition.compile();
-    let consequent = this.consequent.compile();
-    let alternative = this.alternative.compile();
-    if (
-      condition.type !== 'string' &&
-			condition.type !== 'number' &&
-			condition.type !== 'boolean'
-    ){
-      // Handle unresolved condition
-      return new ConstantNode({
-        value: `${condition.value}) ${consequent.value} else ${alternative.value}`,
-        type: 'uncompiledNode',
-        errors: [
-          ...condition.errors,
-          ...consequent.errors,
-          ...alternative.errors,
-        ],
-      });
+  compile(scope){
+    return this.resolve('compile', scope);
+  }
+  roll(scope){
+    return this.resolve('roll', scope);
+  }
+  reduce(scope){
+    return this.resolve('reduce', scope);
+  }
+  resolve(fn, scope){
+    let condition = this.condition[fn](scope);
+    let consequent = this.consequent[fn](scope);
+    let alternative = this.alternative[fn](scope);
+    this.resolve(condition, consequent, alternative);
+    if (condition.value){
+      consequent.inheritDetails([condition, this]);
+      return consequent;
     } else {
-			// So long as the condition reolves, return the correct alternative,
-			// even if it's unresolved
-      if (condition.value){
-        return consequent;
-      } else {
-        return alternative;
-      }
+      alternative.inheritDetails([condition, this]);
+      return alternative;
     }
   }
 }
diff --git a/app/imports/parser/parseTree/IndexNode.js b/app/imports/parser/parseTree/IndexNode.js
index 158da8c6..8014d942 100644
--- a/app/imports/parser/parseTree/IndexNode.js
+++ b/app/imports/parser/parseTree/IndexNode.js
@@ -2,23 +2,35 @@ import ParseNode from '/imports/parser/parseTree/ParseNode.js';
 
 export default class IndexNode extends ParseNode {
   constructor({array, index}) {
-		super();
+		super(...arguments);
     this.array = array;
     this.index = index;
   }
-  compile(){
-    let index = this.index.compile();
-    if (index.constructor.name === 'ConstantNode' && index.type === 'number'){
-      let selection = this.array.values[index.value];
+  resolve(fn, scope){
+    let index = this.index[fn](scope);
+    if (index.isInteger){
+      let selection = this.array.values[index.value - 1];
       if (selection){
-        return selection.compile();
+        let result = selection[fn](scope);
+        result.inheritDetails([index, this]);
+        return result;
       }
     }
     return new IndexNode({
-      array: this.array.compile(),
-      index: this.index.compile(),
+      array: this.array[fn](scope),
+      index: this.index[fn](scope),
+      previousNodes: [this],
     });
   }
+  compile(scope){
+    return this.resolve('compile', scope);
+  }
+  roll(scope){
+    return this.resolve('roll', scope);
+  }
+  reduce(scope){
+    return this.resolve('reduce', scope);
+  }
   toString(){
     return `${this.array.toString()}[${this.index.toString()}]`;
   }
diff --git a/app/imports/parser/parseTree/OperatorNode.js b/app/imports/parser/parseTree/OperatorNode.js
index fa75f315..5b6830d8 100644
--- a/app/imports/parser/parseTree/OperatorNode.js
+++ b/app/imports/parser/parseTree/OperatorNode.js
@@ -3,22 +3,32 @@ import ConstantNode from '/imports/parser/parseTree/ConstantNode.js';
 
 export default class OperatorNode extends ParseNode {
   constructor({left, right, operator, fn}) {
-		super();
+		super(...arguments);
     this.left = left;
     this.right = right;
     this.fn = fn;
     this.operator = operator;
   }
-  compile(){
-    let leftNode = this.left.compile();
-    let rightNode = this.right.compile();
+  compile(scope){
+    return this.resolve('compile', scope);
+  }
+  roll(scope){
+    return this.resolve('roll', scope);
+  }
+  reduce(scope){
+    return this.resolve('reduce', scope);
+  }
+  resolve(fn, scope){
+    let leftNode = this.left[fn](scope);
+    let rightNode = this.right[fn](scope);
     let left, right;
     if (leftNode.type !== 'number' || rightNode.type !== 'number'){
       return new OperatorNode({
         left: leftNode,
         right: rightNode,
         operator: this.operator,
-        fn: this.fn
+        fn: this.fn,
+        previousNodes: [this],
       });
     } else {
       left = leftNode.value;
@@ -44,7 +54,11 @@ export default class OperatorNode extends ParseNode {
       case '>=': result = left >= right; break;
       case '<=': result = left <= right; break;
     }
-    return new ConstantNode({value: result, type: typeof result});
+    return new ConstantNode({
+      value: result,
+      type: typeof result,
+      previousNodes: [this, leftNode, rightNode],
+    });
   }
   toString(){
     let {left, right, operator} = this;
diff --git a/app/imports/parser/parseTree/ParenthesisNode.js b/app/imports/parser/parseTree/ParenthesisNode.js
index 22da9c4b..2df81c3e 100644
--- a/app/imports/parser/parseTree/ParenthesisNode.js
+++ b/app/imports/parser/parseTree/ParenthesisNode.js
@@ -2,15 +2,24 @@ import ParseNode from '/imports/parser/parseTree/ParseNode.js';
 
 export default class ParenthesisNode extends ParseNode {
   constructor({content}) {
-		super();
+		super(...arguments);
     this.content = content;
   }
-  compile(){
-    let content = this.content.compile();
+  compile(scope){
+    return this.resolve('compile', scope);
+  }
+  roll(scope){
+    return this.resolve('roll', scope);
+  }
+  reduce(scope){
+    return this.resolve('reduce', scope);
+  }
+  resolve(fn, scope){
+    let content = this.content[fn](scope);
     if (content.constructor.name === 'ConstantNode'){
       return content;
     } else {
-      return new ParenthesisNode({content});
+      return new ParenthesisNode({content, previousNodes: [this]});
     }
   }
   toString(){
diff --git a/app/imports/parser/parseTree/ParseNode.js b/app/imports/parser/parseTree/ParseNode.js
index 0d8686d3..03f054ac 100644
--- a/app/imports/parser/parseTree/ParseNode.js
+++ b/app/imports/parser/parseTree/ParseNode.js
@@ -1,4 +1,17 @@
 export default class ParseNode {
+  constructor({previousNodes, detail}){
+    this.inheritDetails(previousNodes);
+    if (detail) this.pushDetails([detail]);
+  }
+  inheritDetails(nodes){
+    if (!nodes || !nodes.length) return;
+    nodes.forEach(node => this.pushDetails(node.details));
+  }
+  pushDetails(details){
+    if (!details || !details.length) return;
+    if (!this.details) this.details = [];
+    details.forEach(detail => this.details.push(detail));
+  }
   compile(){
     // Returns a ParseNode, a ConstantNode if possible
     throw new Meteor.Error('Compile not implemented on ' + this.constructor.name);
@@ -7,11 +20,11 @@ export default class ParseNode {
     throw new Meteor.Error('toString not implemented on ' + this.constructor.name);
   }
 	// Compile, but turn rolls into arrays
-  roll(){
-    return this.compile();
+  roll(scope){
+    return this.compile(scope);
   }
 	// Compile, turn rolls into arrays, and reduce those arrays into single values
-	reduce(){
-		return this.roll();
+	reduce(scope){
+		return this.roll(scope);
 	}
 }
diff --git a/app/imports/parser/parseTree/RollArrayNode.js b/app/imports/parser/parseTree/RollArrayNode.js
index d8d60236..fe21abd3 100644
--- a/app/imports/parser/parseTree/RollArrayNode.js
+++ b/app/imports/parser/parseTree/RollArrayNode.js
@@ -1,8 +1,9 @@
 import ParseNode from '/imports/parser/parseTree/ParseNode.js';
+import ConstantNode from '/imports/parser/parseTree/ConstantNode.js';
 
 export default class RollArrayNode extends ParseNode {
   constructor({values}) {
-		super();
+		super(...arguments);
     this.values = values;
   }
   compile(){
@@ -12,6 +13,11 @@ export default class RollArrayNode extends ParseNode {
     return `[${this.values.join(', ')}]`;
   }
   reduce(){
-    //TODO sum and return values
+    let total = this.values.reduce((a, b) => a + b);
+    return new ConstantNode({
+      value: total,
+      type: 'number',
+      previousNodes: [this],
+    });
   }
 }
diff --git a/app/imports/parser/parseTree/RollNode.js b/app/imports/parser/parseTree/RollNode.js
index d2f99379..8f141832 100644
--- a/app/imports/parser/parseTree/RollNode.js
+++ b/app/imports/parser/parseTree/RollNode.js
@@ -1,17 +1,17 @@
 import ParseNode from '/imports/parser/parseTree/ParseNode.js';
-import ArrayNode from '/imports/parser/parseTree/ArrayNode.js';
+import RollArrayNode from '/imports/parser/parseTree/RollArrayNode.js';
 import ErrorNode from '/imports/parser/parseTree/ErrorNode.js';
 
 export default class RollNode extends ParseNode {
   constructor({left, right}) {
-		super();
+		super(...arguments);
     this.left = left;
     this.right = right;
   }
-  compile(){
-    let left = this.left.compile();
-    let right = this.right.compile();
-    return new RollNode({left, right});
+  compile(scope){
+    let left = this.left.compile(scope);
+    let right = this.right.compile(scope);
+    return new RollNode({left, right, previousNodes: [this]});
   }
   toString(){
     if (
@@ -22,19 +22,21 @@ export default class RollNode extends ParseNode {
       return `${this.left.toString()}d${this.right.toString()}`;
     }
   }
-  roll(){
-    let left = this.left.reduce();
-    let right = this.right.reduce();
+  roll(scope){
+    let left = this.left.reduce(scope);
+    let right = this.right.reduce(scope);
     if (!left.isInteger){
       return new ErrorNode({
         node: this,
-        error: 'Number of dice is not an integer'
+        error: 'Number of dice is not an integer',
+        previousNodes: [this, left, right],
       });
     }
     if (!right.isInteger){
       return new ErrorNode({
         node: this,
-        error: 'Dice size is not an integer'
+        error: 'Dice size is not an integer',
+        previousNodes: [this, left, right],
       });
     }
     let number = left.value;
@@ -44,14 +46,18 @@ export default class RollNode extends ParseNode {
     });
     let diceSize = right.value;
     let randomSrc = DDP.randomStream('diceRoller');
-    let rolls = [];
+    let values = [];
     for (let i = 0; i < number; i++){
       let roll = ~~(randomSrc.fraction() * diceSize) + 1
-      rolls.push(roll);
+      values.push(roll);
     }
-    return new ArrayNode({values: rolls});
+    return new RollArrayNode({
+      values,
+      detail: {number, diceSize, values},
+      previousNodes: [this, left, right],
+    });
   }
-  reduce(){
-    this.roll().reduce();
+  reduce(scope){
+    return this.roll(scope).reduce(scope);
   }
 }
diff --git a/app/imports/parser/parseTree/SymbolNode.js b/app/imports/parser/parseTree/SymbolNode.js
index cb855b72..35c2ffab 100644
--- a/app/imports/parser/parseTree/SymbolNode.js
+++ b/app/imports/parser/parseTree/SymbolNode.js
@@ -1,9 +1,10 @@
 import ParseNode from '/imports/parser/parseTree/ParseNode.js';
 import ConstantNode from '/imports/parser/parseTree/ConstantNode.js';
+import ErrorNode from '/imports/parser/parseTree/ErrorNode.js';
 
 export default class SymbolNode extends ParseNode {
   constructor({name}){
-		super();
+		super(...arguments);
     this.name = name;
   }
   toString(){
@@ -13,12 +14,11 @@ export default class SymbolNode extends ParseNode {
     let value = scope && scope[this.name];
     let type = typeof value;
     if (type === 'string' || type === 'number' || type === 'boolean'){
-      return new ConstantNode({value, type});
+      return new ConstantNode({value, type, previousNodes: [this]});
     } else if (type === 'undefined'){
-      return new ConstantNode({
-        value: this.name,
-        type: 'uncompiledNode',
-        errors: [`${this.name} could not be resolved`]
+      return new ErrorNode({
+        node: this,
+        error: `${this.name} could not be resolved`,
       });
     } else {
       throw new Meteor.Error(`Unexpected case: ${this.name} resolved to ${value}`);
diff --git a/app/imports/ui/pages/Parser.vue b/app/imports/ui/pages/Parser.vue
index abcc4e4b..ba8d7683 100644
--- a/app/imports/ui/pages/Parser.vue
+++ b/app/imports/ui/pages/Parser.vue
@@ -18,6 +18,21 @@
           readonly
           label="compiled"
         />
+        <v-text-field
+          v-model="rolled"
+          readonly
+          label="rolled"
+        />
+        <v-text-field
+          v-model="reduced"
+          readonly
+          label="reduced"
+        />
+        <v-textarea
+          v-model="reducedJson"
+          readonly
+          label="reduced"
+        />
       </v-card-text>
     </v-card>
   </div>
@@ -32,6 +47,9 @@ export default {
     output: null,
     compiled: null,
     string: null,
+    rolled: null,
+    reduced: null,
+    reducedJson: null,
   }},
   watch: {
     input(val){
@@ -41,7 +59,11 @@ export default {
       this.output = JSON.stringify(output, null, 2);
       if (!output) return;
       this.string = output;
-      this.compiled = output.compile();
+      let scope = {cat: 1, dog: 2, mouse: 3};
+      this.compiled = output.compile(scope);
+      this.rolled = output.roll(scope);
+      this.reduced = output.reduce(scope);
+      this.reducedJson = JSON.stringify(this.reduced, null, 2)
     }
   },
 }
diff --git a/app/package-lock.json b/app/package-lock.json
index 711f73f9..8f43e02d 100644
--- a/app/package-lock.json
+++ b/app/package-lock.json
@@ -2805,7 +2805,7 @@
     },
     "signal-exit": {
       "version": "3.0.2",
-      "resolved": "https://registry.npmjs.org/signal-exit/-/signal-exit-3.0.2.tgz",
+      "resolved": false,
       "integrity": "sha1-tf3AjxKH6hF4Yo5BXiUTK3NkbG0="
     },
     "simpl-schema": {