diff --git a/HISTORY.md b/HISTORY.md
index a24db427..255cfa1d 100755
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -87,8 +87,9 @@
 * Threads: optimized FOREACH performance for large linked lists
 * German translation update (FINDFIRST, WORD, TEMPORARY?)
 * Threads: also allow numbers as sprite names in SET
-* updated "animation library" (purged unused blocks)
-* updated "audioComp library" (purged unused blocks)
+* updated "animation" library (purged unused blocks)
+* updated "audioComp" library (purged unused blocks)
+* updated "frequency distribution" library (changed PIPE to use EMPTY prim)
 
 ### 2019-05-29
 * Threads, Objects: added "Find First" primitive to lists category
diff --git a/libraries/frequency_distribution_module.xml b/libraries/frequency_distribution_module.xml
index a375a57c..3365773c 100644
--- a/libraries/frequency_distribution_module.xml
+++ b/libraries/frequency_distribution_module.xml
@@ -1 +1 @@
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\ No newline at end of file
+<blocks app="Snap! 5.0, http://snap.berkeley.edu" version="1"><block-definition s="$flash analyze %&apos;data&apos;" type="reporter" category="lists"><comment x="0" y="0" w="149" collapsed="false">returns a frequency analysis of the argument list, represented as a two-column table, where the first column contains the unique values and the second column their occurrences</comment><header></header><code></code><translations></translations><inputs><input type="%l"></input></inputs><script><block s="doReport"><block s="evaluate"><block s="reportJSFunction"><list><l>list</l></list><l>var dict = new Map(),&#xD;    result = [],&#xD;    data = list.asArray(),&#xD;    len = data.length,&#xD;    i;&#xD;for (i = 0; i &lt; len; i += 1) {&#xD;    if (dict.has(data[i])) {&#xD;        dict.set(data[i], dict.get(data[i]) + 1);&#xD;    } else {&#xD;        dict.set(data[i], 1);&#xD;    }&#xD;}&#xD;dict.forEach(function (value, key) {&#xD;    result.push(new List([key, value]));&#xD;});&#xD;return new List(result);</l></block><list><block var="data"/></list></block></block></script></block-definition><block-definition s="$flash group %&apos;data&apos; by %&apos;fn&apos;" type="reporter" category="lists"><header></header><code></code><translations></translations><inputs><input type="%l"></input><input type="%repRing"></input></inputs><script><block s="doReport"><block s="evaluate"><block s="reportJSFunction"><list><l>data</l><l>fn</l><l>proc</l></list><l>return proc.reportAtomicGroup(data, fn);</l></block><list><block var="data"/><block var="fn"/></list></block></block></script></block-definition><block-definition s="$flash sort %&apos;data&apos; by %&apos;fn&apos;" type="reporter" category="lists"><header></header><code></code><translations></translations><inputs><input type="%l"></input><input type="%predRing"></input></inputs><script><block s="doReport"><block s="evaluate"><block s="reportJSFunction"><list><l>data</l><l>fn</l><l>proc</l></list><l>return proc.reportAtomicSort(data, fn);</l></block><list><block var="data"/><block var="fn"/></list></block></block></script></block-definition><block-definition s="histogram of %&apos;data&apos; from: %&apos;floor&apos; to: %&apos;ceiling&apos; interval: %&apos;interval&apos;" type="reporter" category="lists"><header></header><code></code><translations></translations><inputs><input type="%l"></input><input type="%n"></input><input type="%n"></input><input type="%n">1</input></inputs><script><block s="doReport"><custom-block s="fill %l key: %repRing from: %n to: %n interval: %repRing with: %repRing"><custom-block s="$flash sort %l by %predRing"><custom-block s="$flash analyze %l"><block var="data"/></custom-block><block s="reifyPredicate"><autolambda><block s="reportLessThan"><block s="reportListItem"><l>1</l><l/></block><block s="reportListItem"><l>1</l><l/></block></block></autolambda><list></list></block></custom-block><block s="reifyReporter"><autolambda><block s="reportListItem"><l>1</l><l/></block></autolambda><list></list></block><block var="floor"/><block var="ceiling"/><block s="reifyReporter"><autolambda><block s="reportSum"><l></l><block var="interval"/></block></autolambda><list></list></block><block s="reifyReporter"><autolambda><block s="reportNewList"><list><l></l><l>0</l></list></block></autolambda><list></list></block></custom-block></block></script></block-definition><block-definition s="histogram of %&apos;data&apos; grouped by: %&apos;key&apos; from: %&apos;floor&apos; to: %&apos;ceiling&apos; interval: %&apos;interval&apos;" type="reporter" category="lists"><header></header><code></code><translations></translations><inputs><input type="%l"></input><input type="%repRing"></input><input type="%n"></input><input type="%n"></input><input type="%repRing"></input></inputs><script><block s="doReport"><custom-block s="fill %l key: %repRing from: %n to: %n interval: %repRing with: %repRing"><custom-block s="$flash sort %l by %predRing"><custom-block s="$flash group %l by %repRing"><block var="data"/><block var="key"/></custom-block><block s="reifyPredicate"><autolambda><block s="reportLessThan"><block s="reportListItem"><l>1</l><l/></block><block s="reportListItem"><l>1</l><l/></block></block></autolambda><list></list></block></custom-block><block s="reifyReporter"><autolambda><block s="reportListItem"><l>1</l><l/></block></autolambda><list></list></block><block var="floor"/><block var="ceiling"/><block var="interval"/><block s="reifyReporter"><autolambda><block s="reportNewList"><list><l></l><l>0</l><block s="reportNewList"><list></list></block></list></block></autolambda><list></list></block></custom-block></block></script></block-definition><block-definition s="fill %&apos;data&apos; key: %&apos;key&apos; from: %&apos;floor&apos; to: %&apos;ceiling&apos; interval: %&apos;interval&apos; with: %&apos;generator&apos;" type="reporter" category="lists"><comment x="0" y="0" w="103" collapsed="false">add missing entries to a sorted list. 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