add shortcut ~@ for unquote-splice

src/Reader.php

@@ -27,6 +27,8 @@ class Reader
             return $this->readSpecialForm($tokens, $index, 'quasiquote');
         } elseif ($tokens[$index] == "~") {
             return $this->readSpecialForm($tokens, $index, 'unquote');
+        } elseif ($tokens[$index] == "~@") {
+            return $this->readSpecialForm($tokens, $index, 'unquote-splice');
         } elseif ($tokens[$index] == '(') {
             return $this->readList($tokens, $index);
         } elseif ($tokens[$index] == '[') {

src/Tokenizer.php

@@ -101,6 +101,14 @@ class Tokenizer
                     // Other special characters
                     $addCurrent();
                     $tokens[] = $c;
+                } elseif ($c == '@') {
+                    // If the last token was ~ then add @ to it
+                    if (count($tokens) > 0 && $tokens[count($tokens) - 1] == '~') {
+                        $tokens[count($tokens) - 1] .= $c;
+                    } else {
+                        // Otherwise treat it like normal character
+                        $current .= $c;
+                    }
                 } else {
                     // All other characters
                     $current .= $c;

test/ReaderTest.php

@@ -28,6 +28,7 @@ class ReaderTest extends TestCase
             ["'", 'quote'],
             ['`', 'quasiquote'],
             ['~', 'unquote'],
+            ['~@', 'unquote-splice'],
         ];
     }
 

test/TokenizerTest.php

@@ -76,6 +76,9 @@ class TokenizerTest extends TestCase
             // Other non-alphabet characters are symbols
             ["(aa!@#$%^&*-_=+bb<>,./?\\|cc)", ['(', "aa!@#$%^&*-_=+bb<>,./?\\|cc", ')']],
 
+            // @ after ~ is single token, @ anywhere else is normal character
+            ['aa@~@@bb', ['aa@', '~@', '@bb']],
+
             // Strings
             ['"abc"', ['"abc"']],
             ['aa"bb"cc', ['aa', '"bb"', 'cc']],