Some improvements

parsley-grammar/src/main/java/com/albertoventurini/parsley/grammar/Grammar.java

@@ -10,13 +10,22 @@ public abstract class Grammar {
 
     protected abstract Rule commentRule();
 
+    /**
+     * Default whitespace predicate for grammars.
+     * @param c a character
+     * @return true if c is whitespace, false otherwise
+     */
     protected boolean whitespace(final char c) {
         return Character.isWhitespace(c);
     }
 
     public Optional<ParseTree> parse(final String text) {
-        final var ctx = new GrammarContext(text, commentRule(), this::whitespace);
+        final var ctx = new GrammarContext(text, commentRule()) {
+            @Override
+            protected boolean isWhitespace(final char c) {
+                return whitespace(c);
+            }
+        };
         return startRule().apply(ctx);
     }
-
 }

parsley-grammar/src/main/java/com/albertoventurini/parsley/grammar/GrammarContext.java

@@ -2,20 +2,15 @@ package com.albertoventurini.parsley.grammar;
 
 import com.albertoventurini.parsley.grammar.rules.Rule;
 
-import java.util.function.Predicate;
-
-public class GrammarContext extends ParseContext {
+public abstract class GrammarContext extends ParseContext {
     private final Rule commentRule;
-    private final Predicate<Character> whitespacePredicate;
     private boolean inComment;
 
     GrammarContext(
             final String string,
-            final Rule commentRule,
-            final Predicate<Character> whitespacePredicate) {
+            final Rule commentRule) {
         super(string);
         this.commentRule = commentRule;
-        this.whitespacePredicate = whitespacePredicate;
     }
 
     public void advanceToNextToken() {
@@ -63,9 +58,5 @@ public class GrammarContext extends ParseContext {
         }
     }
 
-    private boolean isWhitespace(final char c) {
-        return whitespacePredicate.test(c);
-//        return Character.isWhitespace(c) || c == '\n';
-//        return c != '\n' && Character.isWhitespace(c);
-    }
+    protected abstract boolean isWhitespace(final char c);
 }

parsley-grammar/src/main/java/com/albertoventurini/parsley/grammar/ParseContext.java

@@ -1,7 +1,5 @@
 package com.albertoventurini.parsley.grammar;
 
-import java.util.Arrays;
-
 class ParseContext {
     private final char[] charArr;
     private int cursor;
@@ -51,17 +49,13 @@ class ParseContext {
     }
 
     public String substring(final int start, final int end) {
-        return String.valueOf(Arrays.copyOfRange(charArr, start, end));
+        return new String(charArr, start, end-start);
     }
 
     public String substring(final int start) {
         return substring(start, cursor);
     }
 
-    public String substring() {
-        return String.valueOf(Arrays.copyOfRange(charArr, cursor, charArr.length));
-    }
-
     public boolean matches(final String s) {
         if (cursor + s.length() > charArr.length) {
             return false;