Add array slicing syntax ary[begin:end]

... which evaluates to a copy of the elements with indices in the range
[begin,end), where either index might be omitted, defaulting to 0 or the
length of the string respectively

src/script/C4Aul.h

@@ -132,6 +132,7 @@ enum C4AulBCCType
 {
 	AB_ARRAYA_R,  // array access
 	AB_ARRAYA_V,  // not creating a reference
+	AB_ARRAY_SLICE, // array slicing
 	AB_VARN_R,    // a named var
 	AB_VARN_V,
 	AB_PARN_R,    // a named parameter

src/script/C4AulExec.cpp

@@ -591,6 +591,26 @@ C4Value C4AulExec::Exec(C4AulBCC *pCPos, bool fPassErrors)
 				PopValue();
 				break;
 			}
+			case AB_ARRAY_SLICE:
+			{
+				C4Value &Array = pCurVal[-2];
+				C4Value &StartIndex = pCurVal[-1];
+				C4Value &EndIndex = pCurVal[0];
+
+				// Typcheck
+				if (!Array.ConvertTo(C4V_Array) || Array.GetType() == C4V_Any)
+					throw new C4AulExecError(pCurCtx->Obj, FormatString("array slice: can't access %s as an array!", Array.GetTypeName()).getData());
+				if (!StartIndex.ConvertTo(C4V_Int))
+					throw new C4AulExecError(pCurCtx->Obj, FormatString("array slice: start index of type %s, int expected!", StartIndex.GetTypeName()).getData());
+				if (!EndIndex.ConvertTo(C4V_Int))
+					throw new C4AulExecError(pCurCtx->Obj, FormatString("array slice: end index of type %s, int expected!", EndIndex.GetTypeName()).getData());
+
+				Array.SetArray(Array.GetData().Array->GetSlice(StartIndex._getInt(), EndIndex._getInt()));
+
+				// Remove both indices
+				PopValues(2);
+				break;
+			}
 
 			case AB_STACK:
 				if (pCPos->Par.i < 0)

src/script/C4AulParse.cpp

@@ -833,6 +833,7 @@ static const char * GetTTName(C4AulBCCType e)
 	{
 	case AB_ARRAYA_R: return "ARRAYA_R";  // array access
 	case AB_ARRAYA_V: return "ARRAYA_V";  // not creating a reference
+	case AB_ARRAY_SLICE: return "ARRAY_SLICE";
 	case AB_VARN_R: return "VARN_R";    // a named var
 	case AB_VARN_V: return "VARN_V";
 	case AB_PARN_R: return "PARN_R";    // a named parameter
@@ -1103,6 +1104,7 @@ void C4AulParseState::AddBCC(C4AulBCCType eType, intptr_t X)
 		iStack-=X-1;
 		break;
 
+	case AB_ARRAY_SLICE:
 	case AB_PROPSET:
 		iStack -= 2;
 		break;
@@ -1940,7 +1942,7 @@ int C4AulParseState::Parse_Params(int iMaxCnt, const char * sWarn, C4AulFunc * p
 				{
 				case AB_INT: from = (a->CPos-1)->Par.i ? C4V_Int : C4V_Any; break;
 				case AB_STRING: from = C4V_String; break;
-				case AB_ARRAY: from = C4V_Array; break;
+				case AB_ARRAY: case AB_ARRAY_SLICE: from = C4V_Array; break;
 				case AB_BOOL: from = C4V_Bool; break;
 //          case AB_UNOP: case AB_BINOP: from = C4ScriptOpMap[(a->CPos-1)->Par.i].RetType; break;
 				case AB_FUNC:
@@ -2594,11 +2596,37 @@ void C4AulParseState::Parse_Expression2(int iParentPrio)
 		}
 		case ATT_BOPEN2:
 		{
-			// Access the array
+			// parse either [index], or [start:end] in which case either index is optional
 			Shift();
-			Parse_Expression();
-			Match(ATT_BCLOSE2);
-			AddBCC(AB_ARRAYA_R);
+			if (TokenType == ATT_COLON)
+				AddBCC(AB_INT, 0); // slice with first index missing -> implicit start index zero
+			else
+				Parse_Expression();
+
+			if (TokenType == ATT_BCLOSE2)
+			{
+				Shift();
+				AddBCC(AB_ARRAYA_R);
+			}
+			else if (TokenType == ATT_COLON)
+			{
+				Shift();
+				if (TokenType == ATT_BCLOSE2)
+				{
+					Shift();
+					AddBCC(AB_INT, INT_MAX); // second index missing -> implicit end index GetLength()
+				}
+				else
+				{
+					Parse_Expression();
+					Match(ATT_BCLOSE2);
+				}
+				AddBCC(AB_ARRAY_SLICE);
+			}
+			else
+			{
+				UnexpectedToken("']' or ':'");
+			}
 			break;
 		}
 		case ATT_CALL:

src/script/C4ValueList.cpp

@@ -253,6 +253,30 @@ C4ValueArray * C4ValueArray::IncRef()
 	return this;
 }
 
+C4ValueArray * C4ValueArray::GetSlice(int32_t startIndex, int32_t endIndex)
+{
+	// adjust indices so that the default end index works and that negative numbers count backwards from the end of the string
+	if (startIndex > iSize) startIndex = iSize;
+	else if (startIndex < -iSize) throw new C4AulExecError(NULL, "Array slice: invalid start index");
+	else if (startIndex < 0) startIndex += iSize;
+
+	if (endIndex > iSize) endIndex = iSize;
+	else if (endIndex < -iSize) throw new C4AulExecError(NULL, "Array slice: invalid end index");
+	else if (endIndex < 0) endIndex += iSize;
+
+	if (startIndex == 0 && endIndex == iSize)
+	{
+		return IncRef();
+	}
+	else
+	{
+		C4ValueArray* NewArray = new C4ValueArray(std::max(0, endIndex - startIndex));
+		for (int i = startIndex; i < endIndex; ++i)
+			NewArray->pData[i - startIndex] = pData[i];
+		return NewArray;
+	}
+}
+
 C4ValueArray * C4ValueArray::SetLength(int32_t size)
 {
 	if (iRefCnt > 1)

src/script/C4ValueList.h

@@ -81,6 +81,8 @@ public:
 	// Add Reference, return self or new copy if necessary
 	C4ValueArray * IncRef();
 	C4ValueArray * IncElementRef();
+	// Return sub-array [startIndex, endIndex), or reference for [0, iSize)
+	C4ValueArray * GetSlice(int32_t startIndex, int32_t endIndex);
 	// Change length, return self or new copy if necessary
 	C4ValueArray * SetLength(int32_t size);
 	void DecRef();