diff --git a/lib/and.js b/lib/and.js
index f18a4d0..43d5af9 100644
--- a/lib/and.js
+++ b/lib/and.js
@@ -25,10 +25,12 @@ function and(...predicates) {
         unform: value => unform(predicates[0], value),
         gen: () => gen(predicates[0]),
         describe: () => [and.name, ...describe(predicates)],
-        explain: (value, {via}) => {
+        explain: function*(value, {via}) {
             const problems = _.map(predicates, predicate => explainData(predicate, value, {via}));
             const found = _.find(problems, p => !_.isNull(p));
-            return _.isUndefined(found) ? null : {problems: found.problems};
+            if (found) {
+                yield found.problems[0];
+            }
         }
     };
 }
diff --git a/lib/def.js b/lib/def.js
index 61f2a81..f4f184b 100644
--- a/lib/def.js
+++ b/lib/def.js
@@ -20,7 +20,11 @@ function createArraySpec(predicate) {
     return {
         conform: (value, unwrap = false) => conform(value, unwrap, _.partial(_.includes, predicate)),
         describe: () => predicate,
-        explain: value => _.includes(predicate, value) ? null : getExplanation(value),
+        explain: function*(value) {
+            if (!_.includes(predicate, value)) {
+                yield getExplanation(value);
+            }
+        },
         gen: () => tcg.null.then(() => tcg.return(_.sample(predicate)))
     };
 }
@@ -29,9 +33,11 @@ function createFunctionSpec(predicate, gen) {
     return {
         conform: (value, unwrap = false) => conform(value, unwrap, predicate),
         unform: _.identify,
-        explain: (value, options) => {
+        explain: function*(value, options) {
             options.pred = _.isEmpty(predicate.name) || predicate.name === 'anonymous' ? `${predicate}` : predicate.name;
-            return predicate(value) ? null : getExplanation(value, options);
+            if (!predicate(value)) {
+                yield getExplanation(value, options);
+            }
         },
         gen: gen ? gen : () => functions.gen(predicate)
     };
@@ -39,13 +45,11 @@ function createFunctionSpec(predicate, gen) {
 
 function getExplanation(value, {path, pred = unknownString, via}) {
     return {
-        problems: [{
-            path,
-            pred,
-            val: value,
-            via,
-            'in': []
-        }]
+        path,
+        pred,
+        val: value,
+        via,
+        'in': []
     };
 }
 
diff --git a/lib/explainData.js b/lib/explainData.js
index 9a3ede6..0cdb255 100644
--- a/lib/explainData.js
+++ b/lib/explainData.js
@@ -1,14 +1,15 @@
 const _ = require('lodash');
 
 const {spec: specize} = require('./def');
-const {isFunction, isString} = require('./utils');
+const {isString} = require('./utils');
 
 function explainData(spec, value, {path =  [], via = []} = {}) {
     const lookup = specize(spec);
     if (lookup) {
         const name = specName(spec);
         const viaOut = _.isUndefined(name) ? via : [name, ...via];
-        return lookup.explain(value, {path, pred: name, via: viaOut});
+        const problems = [...lookup.explain(value, {path, pred: name, via: viaOut})];
+        return _.isEmpty(problems) ? null : {problems};
     } else {
         throw new Error(`Unable to resolve spec ${spec}`);
     }
diff --git a/lib/intIn.js b/lib/intIn.js
index 5c5ee3f..c3b042b 100644
--- a/lib/intIn.js
+++ b/lib/intIn.js
@@ -10,9 +10,7 @@ function intIn(start, end) {
         unform: _.identity,
         gen: () => tcg.intWithin(start, end - 1),
         describe: () => ['and', 'isInt', ['isIntInRange', start, end]],
-        explain: (value, {via}) => {
-            const problems = [];
-            return _.isEmpty(problems) ? null : {problems};
+        explain: function*(value, {via}) {
         }
     };
 }
diff --git a/lib/nilable.js b/lib/nilable.js
index 2918095..d2522b2 100644
--- a/lib/nilable.js
+++ b/lib/nilable.js
@@ -15,20 +15,18 @@ function nilable(predicate) {
         unform: _.identity,
         gen: () => tcg.null.then(() => _.random(10) < 2 ? tcg.null : gen(predicate)),
         describe: () => [nilable.name, ...describe([predicate])],
-        explain: (value, {via}) => {
-            return _.isNull(value) || isValid(predicate, value) ? null : 
-                {
-                    problems: [
-                        explainData(predicate, value, {path: ['pred'], via}).problems[0],
-                        {
-                            path: ['null'],
-                            pred: 'isNull',
-                            val: value,
-                            via,
-                            'in': []
-                        }
-                    ]
-                };
+        explain: function*(value, {via}) {
+            if (!(_.isNull(value) || isValid(predicate, value))) {
+                yield explainData(predicate, value, {path: ['pred'], via}).problems[0];
+                
+                yield {
+                    path: ['null'],
+                    pred: 'isNull',
+                    val: value,
+                    via,
+                    'in': []
+                }
+            }
         }
     };
 }
diff --git a/lib/or.js b/lib/or.js
index 1b8771f..ecf255b 100644
--- a/lib/or.js
+++ b/lib/or.js
@@ -25,9 +25,13 @@ function or(...predicates) {
         },
         gen: () => tcg.null.then(() => gen(_.sample(pairs)[1])),
         describe: () => [or.name, ...describe(predicates)],
-        explain: (value, {via}) => {
+        explain: function*(value, {via}) {
             const problems = _.map(pairs, ([k, predicate]) => explainData(predicate, value, {path: [k], via}));
-            return _.some(problems, _.isNull) ? null : {problems: _.flatten(_.map(problems, 'problems'))};
+            if (!_.some(problems, _.isNull)) {
+                for (let i = 0; i < problems.length; i++) {
+                    yield problems[i].problems[0];
+                }
+            }
         }
     };
 }
diff --git a/lib/plus.js b/lib/plus.js
index f0d1191..f91c372 100644
--- a/lib/plus.js
+++ b/lib/plus.js
@@ -17,44 +17,39 @@ function plus(spec) {
         unform: _.identity,
         gen: () => tcg.null.then(() => tcg.array(gen(spec), {size: _.random(1, 5)})),
         describe: () => [plus.name, ...describe([spec])],
-        explain: (values, {via}) => {
-            const problems = [];
-            explainEmptyInput(problems, values, via);
-            if (_.isEmpty(problems)) {
-                explainValidInput(problems, spec, values, via);
-            }
-            return _.isEmpty(problems) ? null : {problems};
+        explain: function*(values, {via}) {
+            yield* explainLength(values, via);
+            yield* explainInvalid(values, spec, via);
         }
     };
 }
 
-function explainEmptyInput(problems, values, via) {
-    if (values.length === 0) {
-        problems.push({
+function* explainLength(values, via) {
+    if (_.isEmpty(values)) {
+        yield {
             path: [],
             reason: 'Insufficient input',
             val: values,
             via,
             'in': []
-        });
+        };
     }
-    return problems;
 }
 
-function explainValidInput(problems, spec, values, via) {
+function* explainInvalid(values, spec, via) {
     const index = _.findIndex(values, value => !isValid(spec, value));
     if (index !== -1) {
         const val = values[index];
+        console.log('***', explainData(spec, val));
         const pred = explainData(spec, val).problems[0].pred;
-        problems.push({
+        yield {
             path: [],
             pred,
             val,
             via,
             'in': [index]
-        });    
+        };
     }
-    return problems;
 }
 
 module.exports = plus;
diff --git a/lib/tuple.js b/lib/tuple.js
index 19109df..20fea19 100644
--- a/lib/tuple.js
+++ b/lib/tuple.js
@@ -14,15 +14,17 @@ function tuple(...predicates) {
         unform: _.identity,
         gen: () => _.map(predicates, gen),
         describe: () => [tuple.name, ...describe(predicates)],
-        explain: (value, {via}) => {
+        explain: function*(value, {via}) {
             const f = new Function('values', `return values.length === ${predicates.length}`);
-            return explainPredicate(f, value, {via});
+            yield* explainPredicate(f, value, {via});
         }
     };
 }
 
-function explainPredicate(pred, value, options) {
-    return pred(value) ? null : explainData(pred, value, options);
+function* explainPredicate(pred, value, options) {
+    if (!pred(value)) {
+        yield explainData(pred, value, options).problems[0];
+    }
 }
 
 module.exports = tuple;