Implement threshold under

3 files changed, 18 insertions, 0 deletions

diff --git a/src/dice.js b/src/dice.js
index e580c9d..53d337d 100644
--- a/src/dice.js
+++ b/src/dice.js
@@ -214,6 +214,21 @@ const threshold = (die1, die2) => {
   }
 }
 
+const thresholdLow = (die1, die2) => {
+  return () => {
+    const cutoff = roll(die1)
+
+    return die2().map(die => {
+      return () => {
+        if (die() <= cutoff) {
+          return 1
+        } else {
+          return 0
+        }
+      }
+    })
+  }
+}
 
 exports.pool = pool
 exports.roll = roll
@@ -231,3 +246,4 @@ exports.keepLow = keepLow
 exports.again = again
 exports.againUnder = againUnder
 exports.threshold = threshold
+exports.thresholdLow = thresholdLow
diff --git a/src/lexer.js b/src/lexer.js
index f33dc87..ba3d3a5 100644
--- a/src/lexer.js
+++ b/src/lexer.js
@@ -29,6 +29,7 @@ newLexemeType('k', 'k')
 newLexemeType('A', 'A')
 newLexemeType('a', 'a')
 newLexemeType('T', 'T')
+newLexemeType('t', 't')
 
 const lex = (expressionString) => {
   let lexemes = []
diff --git a/src/parser.js b/src/parser.js
index f8e2a5b..adb4b9b 100644
--- a/src/parser.js
+++ b/src/parser.js
@@ -67,6 +67,7 @@ newDieOperation('k')
 newDieOperation('A')
 newDieOperation('a')
 newDieOperation('T')
+newDieOperation('t')
 
 newInfix('bigPlus', 20, { type: 'add' })
 newInfix('bigMinus', 20, { type: 'subtract' })