added string interpolation support

TestHScript.hx

@@ -252,6 +252,14 @@ class TestHScript extends TestCase {
 		assertScript('var newMap = [{a:"a"}=>"foo", objKey=>"bar"]; newMap[objKey];', 'bar', vars);
 	}
 
+	function testStringInterpolation():Void {
+		assertScript("var a = 5; 'a is ${a}'", 'a is 5');
+		assertScript("var a = 5; 'a is ${a + 1}'", 'a is 6');
+		assertScript("var a = 5; 'a is ${if (a > 3) \"big\" else \"small\"}'", 'a is big');
+		assertScript("var a = 5; 'a is ${switch (a) { case 0: \"zero\"; case 5: \"five\"; default: \"other\"; }}'", 'a is five');
+		assertScript("'Hello, ${{var val = false; if (val) \"world\" else {var num = 5 + 3; 'userid_${num}';}}}!'", 'Hello, userid_8!');
+	}
+
 	static function main() {
 		#if ((haxe_ver < 4) && php)
 		// uncaught exception: The each() function is deprecated. This message will be suppressed on further calls (errno: 8192)

hscript/Expr.hx

@@ -21,10 +21,15 @@
  */
 package hscript;
 
+enum StringKind {
+	DoubleQuotes;
+	SingleQuotes;
+}
+
 enum Const {
 	CInt( v : Int );
 	CFloat( f : Float );
-	CString( s : String );
+	CString( s : String , ?kind : StringKind);
 }
 
 #if hscriptPos

hscript/Parser.hx

@@ -354,6 +354,19 @@ class Parser {
 				e = mk(EIdent(id));
 			return isBlock(e) ? e : parseExprNext(e);
 		case TConst(c):
+			if (c.match(CString(_, SingleQuotes)))
+			{
+				var ex = makeInterpolatedStr(tk);
+				if (ex.length == 1)
+					return parseExprNext(ex[0]);
+				else
+				{
+					var result = ex[0];
+					for (i in 1...ex.length)
+						result = makeBinop("+", result, ex[i]);
+					return parseExprNext(mk(EParent(result), p1));
+				}
+			}
 			return parseExprNext(mk(EConst(c)));
 		case TPOpen:
 			tk = token();
@@ -644,6 +657,143 @@ class Parser {
 		}
 	}
 
+	function makeInterpolatedStr(tk:Token):Array<Expr> {
+		var ex = new Array();
+		var s = switch(tk)
+		{
+		case TConst(c):
+			switch(c)
+			{
+			case CString(s):
+				s;
+			case _:
+				null;
+			}
+		case _:
+			null;
+		}
+
+		if (s == null)
+			error(ECustom("Invalid string literal"), tokenMin, tokenMax);
+
+		var nextStr = "";
+		function pushNextStr() {
+			if (nextStr != "") {
+				ex.push(mk(EConst(CString(nextStr)), tokenMin, tokenMax));
+				nextStr = "";
+			}
+		}
+
+		var i = 0;
+		var c = s.charCodeAt(i);
+		while (true)
+		{
+			if (StringTools.isEof(c))
+			{
+				pushNextStr();
+				break;
+			}
+
+			if (c != "$".code)
+			{
+				nextStr += String.fromCharCode(c);
+				c = s.charCodeAt(++i);
+				continue;
+			}
+
+			c = s.charCodeAt(++i);
+			if (c >= 48 && c <= 57 || c == "$".code)
+			{
+				nextStr += "$" + String.fromCharCode(c);
+				c = s.charCodeAt(++i);
+				continue;
+			}
+
+			if( idents[c] ) {
+				var id = String.fromCharCode(c);
+				while( true ) {
+					c = s.charCodeAt(++i);
+					if( StringTools.isEof(c) ) c = 0;
+					if( !idents[c] ) {
+						break;
+					}
+					id += String.fromCharCode(c);
+				}
+				pushNextStr();
+				ex.push(mk(EIdent(id), tokenMin, tokenMax));
+				nextStr = "";
+			}
+			else if (c == "{".code)
+			{
+				pushNextStr();
+				nextStr = "";
+				var lastInput = input;
+				var lastReadPos = readPos;
+				var lastChar = char;
+				var lastTokens = tokens;
+
+				function reset()
+				{
+					input = s;
+					readPos = i;
+					char = -1;
+					#if hscriptPos
+					tokens = new List();
+					#else
+					tokens = new haxe.ds.GenericStack<Token>();
+					#end
+				}
+				reset();
+				var brOpens = -1;
+				while( true ) {
+					var tk = token();
+					if ( tk == TBrOpen )
+					{
+						if (brOpens == -1)
+							brOpens = 0;
+						brOpens++;
+					}
+					else if ( tk == TBrClose )
+					{
+						if (brOpens == -1)
+							unexpected(tk);
+						brOpens--;
+						if (brOpens <= 0)
+							break;
+					}
+					if( tk == TEof )
+						error(EUnterminatedString, currentPos, currentPos);
+				}
+				var endPos = readPos - 1;
+				reset();
+				// cool hack to quickly close expressions
+				input = s.substring(i, endPos) + ";}";
+				readPos = 0;
+				var a = new Array();
+				while( true ) {
+					var tk = token();
+					if( tk == TEof ) break;
+					push(tk);
+					parseFullExpr(a);
+				}
+				pushNextStr();
+				ex.push(mk(EBlock(a),0));
+				nextStr = "";
+				input = lastInput;
+				i = endPos + 1;
+				c = s.charCodeAt(i);
+				readPos = lastReadPos;
+				char = lastChar;
+				tokens = lastTokens;
+			}
+			else
+			{
+				nextStr += "$";
+			}
+		}
+		return ex;
+	}
+
 	function parseStructure(id) {
 		#if hscriptPos
 		var p1 = tokenMin;
@@ -1385,6 +1535,10 @@ class Parser {
 	inline function readChar() {
 		return StringTools.fastCodeAt(input, readPos++);
 	}
+
+	inline function peekChar() {
+		return StringTools.fastCodeAt(input, readPos);
+	}
 
 	function readString( until ) {
 		var c = 0;
@@ -1438,7 +1592,36 @@ class Parser {
 				esc = true;
 			else if( c == until )
 				break;
-			else {
+			else if (c == '$'.code && peekChar() == '{'.code)
+			{
+				b.addChar('$'.code);
+				var brOpens = -1;
+				while (true)
+				{
+					c = readChar();
+					if (StringTools.isEof(c))
+					{
+						line = old;
+						error(EUnterminatedString, p1, p1);
+						break;
+					}
+					b.addChar(c);
+					if ( c == '{'.code )
+					{
+						if (brOpens == -1)
+							brOpens = 0;
+						brOpens++;
+					}
+					else if ( c == '}'.code )
+					{
+						if (brOpens == -1)
+							invalidChar(c);
+						brOpens--;
+						if (brOpens <= 0)
+							break;
+					}
+				}
+			} else {
 				if( c == 10 ) line++;
 				b.addChar(c);
 			}
@@ -1589,7 +1772,8 @@ class Parser {
 			case "}".code: return TBrClose;
 			case "[".code: return TBkOpen;
 			case "]".code: return TBkClose;
-			case "'".code, '"'.code: return TConst( CString(readString(char)) );
+			case "'".code: return TConst( CString(readString(char), SingleQuotes) );
+			case '"'.code: return TConst( CString(readString(char), DoubleQuotes) );
 			case "?".code:
 				char = readChar();
 				if( char == ".".code )