3 files changed, 18 insertions, 0 deletions
diff --git a/src/dice.js b/src/dice.js
index 9bc53d7..e96aca9 100644
--- a/src/dice.js
+++ b/src/dice.js
@@ -73,6 +73,21 @@ const explode = (die1, die2) => {
   }
 }
 
+const explodeUnder = (die1, die2) => {
+  return () => {
+    const explodeOn = roll(die1)
+    return die2().map(die => () => {
+      let lastRoll = die()
+      let total = lastRoll
+      while (lastRoll <= explodeOn) {
+        lastRoll = die()
+        total += lastRoll
+      }
+      return total
+    })
+  }
+}
+
 const keepHigh = (die1, die2) => {
   return () => {
     const numberToKeep = roll(die1)
@@ -174,6 +189,7 @@ exports.bonusAdd = bonusAdd
 exports.bonusSubtract = bonusSubtract
 exports.negative = negative
 exports.explode = explode
+exports.explodeUnder = explodeUnder
 exports.keepHigh = keepHigh
 exports.keepLow = keepLow
 exports.again = again
diff --git a/src/lexer.js b/src/lexer.js
index f316147..7eb95b0 100644
--- a/src/lexer.js
+++ b/src/lexer.js
@@ -23,6 +23,7 @@ newLexemeType('minus', '-')
 newLexemeType('(', '\\(')
 newLexemeType(')', '\\)')
 newLexemeType('E', 'E')
+newLexemeType('e', 'e')
 newLexemeType('K', 'K')
 newLexemeType('k', 'k')
 newLexemeType('A', 'A')
diff --git a/src/parser.js b/src/parser.js
index 0201d05..124d686 100644
--- a/src/parser.js
+++ b/src/parser.js
@@ -61,6 +61,7 @@ newSymbol('d', (parser) => {
   }
 })
 newDieOperation('E')
+newDieOperation('e')
 newDieOperation('K')
 newDieOperation('k')
 newDieOperation('A')