From 8b46bbb1c0b3aefea7fa683b53165e497a14056d Mon Sep 17 00:00:00 2001
From: Jon Siwek <jsiwek@ncsa.illinois.edu>
Date: Mon, 7 Jan 2013 13:29:05 -0600
Subject: [PATCH] Change substring index notation to use a colon (addresses
 #422).

String slice notation is written as `s[1:2]` instead of `s[1, 2]`
because the later is ambiguous with composite index types.
---
 src/Expr.cc                                  | 16 +++++++++++++-
 src/Expr.h                                   |  2 +-
 src/parse.y                                  |  8 +++++++
 testing/btest/core/leaks/string-indexing.bro | 22 ++++++++++----------
 testing/btest/language/string-indexing.bro   | 22 ++++++++++----------
 5 files changed, 46 insertions(+), 24 deletions(-)

diff --git a/src/Expr.cc b/src/Expr.cc
index eef0e7b69e..b3127d6a7f 100644
--- a/src/Expr.cc
+++ b/src/Expr.cc
@@ -2801,12 +2801,26 @@ bool AssignExpr::DoUnserialize(UnserialInfo* info)
 	return UNSERIALIZE(&is_init);
 	}
 
-IndexExpr::IndexExpr(Expr* arg_op1, ListExpr* arg_op2)
+IndexExpr::IndexExpr(Expr* arg_op1, ListExpr* arg_op2, bool is_string_slice)
 : BinaryExpr(EXPR_INDEX, arg_op1, arg_op2)
 	{
 	if ( IsError() )
 		return;
 
+	if ( is_string_slice )
+		{
+		if ( ! IsString(op1->Type()->Tag()) )
+			ExprError("slice notation indexing can apply only to strings");
+		}
+	else if ( IsString(op1->Type()->Tag()) )
+		{
+		if ( arg_op2->Exprs().length() != 1 )
+			ExprError("invalid string index expression");
+		}
+
+	if ( IsError() )
+		return;
+
 	int match_type = op1->Type()->MatchesIndex(arg_op2);
 	if ( match_type == DOES_NOT_MATCH_INDEX )
 		SetError("not an index type");
diff --git a/src/Expr.h b/src/Expr.h
index ea17c735b5..ac3ab0f4f2 100644
--- a/src/Expr.h
+++ b/src/Expr.h
@@ -646,7 +646,7 @@ protected:
 
 class IndexExpr : public BinaryExpr {
 public:
-	IndexExpr(Expr* op1, ListExpr* op2);
+	IndexExpr(Expr* op1, ListExpr* op2, bool is_string_slice = false);
 
 	int CanAdd() const;
 	int CanDel() const;
diff --git a/src/parse.y b/src/parse.y
index a16b742728..090786647e 100644
--- a/src/parse.y
+++ b/src/parse.y
@@ -418,6 +418,14 @@ expr:
 			$$ = new IndexExpr($1, $3);
 			}
 
+	|	expr '[' expr ':' expr ']'
+			{
+			set_location(@1, @6);
+			ListExpr* le = new ListExpr($3);
+			le->Append($5);
+			$$ = new IndexExpr($1, le, true);
+			}
+
 	|	expr '$' TOK_ID
 			{
 			set_location(@1, @3);
diff --git a/testing/btest/core/leaks/string-indexing.bro b/testing/btest/core/leaks/string-indexing.bro
index 40af2317e6..f9ea000ef9 100644
--- a/testing/btest/core/leaks/string-indexing.bro
+++ b/testing/btest/core/leaks/string-indexing.bro
@@ -11,16 +11,16 @@ event new_connection(c: connection)
 	{
 	local s = "0123456789";
 	print s[1];
-	print s[1,2];
-	print s[1,6];
-	print s[0,20];
+	print s[1:2];
+	print s[1:6];
+	print s[0:20];
 	print s[-2];
-	print s[-3,-1];
-	print s[-1,-10];
-	print s[-1,0];
-	print s[-1,5];
-	print s[20, 23];
-	print s[-20, 23];
-	print s[0,5][2];
-	print s[0,5][1,3][0];
+	print s[-3:1];
+	print s[-1:10];
+	print s[-1:0];
+	print s[-1:5];
+	print s[20:23];
+	print s[-20:23];
+	print s[0:5][2];
+	print s[0:5][1:3][0];
 	}
diff --git a/testing/btest/language/string-indexing.bro b/testing/btest/language/string-indexing.bro
index d05c1b6c5e..f991b3c5fa 100644
--- a/testing/btest/language/string-indexing.bro
+++ b/testing/btest/language/string-indexing.bro
@@ -3,15 +3,15 @@
 
 local s = "0123456789";
 print s[1];
-print s[1,2];
-print s[1,6];
-print s[0,20];
+print s[1:2];
+print s[1:6];
+print s[0:20];
 print s[-2];
-print s[-3,-1];
-print s[-1,-10];
-print s[-1,0];
-print s[-1,5];
-print s[20, 23];
-print s[-20, 23];
-print s[0,5][2];
-print s[0,5][1,3][0];
+print s[-3:-1];
+print s[-1:-10];
+print s[-1:0];
+print s[-1:5];
+print s[20:23];
+print s[-20:23];
+print s[0:5][2];
+print s[0:5][1:3][0];