String Interpolation

src/scanner.c

@@ -23,6 +23,7 @@ static Token identifier(Scanner *scanner);
 static Token number(Scanner *scanner);
 static Token string(Scanner *scanner);
 static void skipWhitespace(Scanner *scanner);
+static Token interpolatedString(Scanner *scanner);
 
 /**
  * Initialize the scanner's state
@@ -111,6 +112,11 @@ Token scanToken(Scanner *scanner) {
     return makeToken(scanner, TOKEN_MODULO);
   case '"':
     return string(scanner);
+  case '$':
+    if (match(scanner, '"')) {
+      return interpolatedString(scanner);
+    }
+    break;
   }
 
   return errorToken(scanner, "Unexpected character.");
@@ -277,6 +283,20 @@ static Token number(Scanner *scanner) {
   return makeToken(scanner, TOKEN_NUMBER);
 }
 
+static Token interpolatedString(Scanner *scanner) {
+  while (peek(scanner) != '"' && !isAtEnd(scanner)) {
+    advance(scanner);
+  }
+
+  if (isAtEnd(scanner)) {
+    return errorToken(scanner, "Unterminated interpolated string.");
+  }
+
+  advance(scanner); // closing quote
+
+  return makeToken(scanner, TOKEN_INTERPOLATED_STRING);
+}
+
 static Token string(Scanner *scanner) {
   TRACELN("scanner.string()");
 

src/token.c

@@ -44,6 +44,8 @@ const char *tokenTypeToString(TokenType type) {
     return "TOKEN_IDENTIFIER";
   case TOKEN_STRING:
     return "TOKEN_STRING";
+  case TOKEN_INTERPOLATED_STRING:
+    return "TOKEN_INTERPOLATED_STRING";
   case TOKEN_NUMBER:
     return "TOKEN_NUMBER";
   case TOKEN_AND:

src/token.h

@@ -30,6 +30,7 @@ typedef enum {
   // Literals.
   TOKEN_IDENTIFIER,
   TOKEN_STRING,
+  TOKEN_INTERPOLATED_STRING,
   TOKEN_NUMBER,
   // Keywords.
   TOKEN_AND,

tests/strings/string_interpolation.lox

@@ -0,0 +1,3 @@
+var name = "World";
+
+print $"Hello {name}";

tests/strings/string_interpolation.lox.err

@@ -0,0 +1,81 @@
+== is ==
+0000    2 OP_GET_GLOBAL       0 'typeof'
+0002    | OP_GET_LOCAL        1
+0004    | OP_CALL             1
+0006    | OP_GET_LOCAL        2
+0008    | OP_EQUAL
+0009    | OP_RETURN
+0010    3 OP_NIL
+0011    | OP_RETURN
+== is_function ==
+0000    6 OP_GET_GLOBAL       0 'is'
+0002    | OP_GET_LOCAL        1
+0004    | OP_CONSTANT         1 'function'
+0006    | OP_CALL             2
+0008    | OP_RETURN
+0009    7 OP_NIL
+0010    | OP_RETURN
+== is_number ==
+0000   10 OP_GET_GLOBAL       0 'is'
+0002    | OP_GET_LOCAL        1
+0004    | OP_CONSTANT         1 'number'
+0006    | OP_CALL             2
+0008    | OP_RETURN
+0009   11 OP_NIL
+0010    | OP_RETURN
+== is_string ==
+0000   14 OP_GET_GLOBAL       0 'is'
+0002    | OP_GET_LOCAL        1
+0004    | OP_CONSTANT         1 'string'
+0006    | OP_CALL             2
+0008    | OP_RETURN
+0009   15 OP_NIL
+0010    | OP_RETURN
+== is_bool ==
+0000   18 OP_GET_GLOBAL       0 'is'
+0002    | OP_GET_LOCAL        1
+0004    | OP_CONSTANT         1 'bool'
+0006    | OP_CALL             2
+0008    | OP_RETURN
+0009   19 OP_NIL
+0010    | OP_RETURN
+== is_nil ==
+0000   22 OP_GET_GLOBAL       0 'is'
+0002    | OP_GET_LOCAL        1
+0004    | OP_CONSTANT         1 'nil'
+0006    | OP_CALL             2
+0008    | OP_RETURN
+0009   23 OP_NIL
+0010    | OP_RETURN
+== is_empty ==
+0000   26 OP_GET_GLOBAL       0 'is_string'
+0002    | OP_GET_LOCAL        1
+0004    | OP_CALL             1
+0006    | OP_JUMP_IF_FALSE    6 -> 19
+0009    | OP_POP
+0010    | OP_GET_GLOBAL       1 'len'
+0012    | OP_GET_LOCAL        1
+0014    | OP_CALL             1
+0016    | OP_CONSTANT         2 '0.000000'
+0018    | OP_EQUAL
+0019    | OP_RETURN
+0020   27 OP_NIL
+0021    | OP_RETURN
+== <script> ==
+0000    3 OP_CLOSURE          1 <fn is>
+0002    | OP_DEFINE_GLOBAL    0 'is'
+0004    7 OP_CLOSURE          3 <fn is_function>
+0006    | OP_DEFINE_GLOBAL    2 'is_function'
+0008   11 OP_CLOSURE          5 <fn is_number>
+0010    | OP_DEFINE_GLOBAL    4 'is_number'
+0012   15 OP_CLOSURE          7 <fn is_string>
+0014    | OP_DEFINE_GLOBAL    6 'is_string'
+0016   19 OP_CLOSURE          9 <fn is_bool>
+0018    | OP_DEFINE_GLOBAL    8 'is_bool'
+0020   23 OP_CLOSURE         11 <fn is_nil>
+0022    | OP_DEFINE_GLOBAL   10 'is_nil'
+0024   27 OP_CLOSURE         13 <fn is_empty>
+0026    | OP_DEFINE_GLOBAL   12 'is_empty'
+0028   28 OP_NIL
+0029    | OP_RETURN
+[line 3] Error at '$"Hello {name}"' (TOKEN_INTERPOLATED_STRING): Expect expression.

tests/strings/string_interpolation.lox.exit

@@ -0,0 +1 @@
+65