Lex and parse keepHigh

2 files changed, 15 insertions, 0 deletions

diff --git a/src/lexer.js b/src/lexer.js
index 85579fb..fd0d0a3 100644
--- a/src/lexer.js
+++ b/src/lexer.js
@@ -25,6 +25,7 @@ newLexemeType('-', '-')
 newLexemeType('(', '\\(')
 newLexemeType(')', '\\)')
 newLexemeType('E', 'E')
+newLexemeType('K', 'K')
 newSkippableLexeme('whitespace', '\\s+')
 
 const lex = (expressionString) => {
diff --git a/src/parser.js b/src/parser.js
index 9479abc..5e9960a 100644
--- a/src/parser.js
+++ b/src/parser.js
@@ -6,6 +6,8 @@ let throwSyntaxError = () => {
   throw new Error('Syntax error: unexpected token')
 }
 
+const dieBindingPower = 30
+
 let newSymbol = (type, nud, lbp, led) => {
   symbols[type] = {
     type,
@@ -33,6 +35,16 @@ newSymbol('(', function(parser) {
 
 newSymbol(')')
 
+const newDieOperation = (symbol, nud = null) => {
+  newSymbol(symbol, nud, dieBindingPower, (left, parser) => {
+    return {
+      type: symbol,
+      left: left,
+      right: parser.expression(dieBindingPower - 1)
+    }
+  })
+}
+
 newSymbol('d', (parser) => {
   return {
     type: 'd',
@@ -55,6 +67,8 @@ newSymbol('E', null, 30, (left, parser) => {
   }
 })
 
+newDieOperation('K')
+
 newSymbol('+', null, 20, (left, parser) => {
   return {
     type: 'add',