C# VList.Slice方法代码示例

		static VList<Pair<VList<LNode>,LNode>> GetCases(VList<LNode> body, IMessageSink sink)
		{
			var pairs = VList<Pair<VList<LNode>,LNode>>.Empty;
			for (int i = 0; i < body.Count; i++) {
				bool isDefault;
				if (body[i].Calls(S.Lambda, 2)) {
					var key = new VList<LNode>(body[i][0].WithoutOuterParens());
					pairs.Add(Pair.Create(key, AutoStripBraces(body[i][1])));
				} else if ((isDefault = IsDefaultLabel(body[i])) || body[i].CallsMin(S.Case, 1)) {
					var alts = isDefault ? VList<LNode>.Empty : body[i].Args.SmartSelect(pat => AutoStripBraces(pat));
					int bodyStart = ++i;
					for (; i < body.Count && !IsDefaultLabel(body[i]) && !body[i].CallsMin(S.Case, 1); i++) {
					}
					LNode handler;
					if (i == bodyStart + 1)
						handler = body[bodyStart];
					else
						handler = F.Braces(body.Slice(bodyStart, i - bodyStart));
					pairs.Add(Pair.Create(alts, handler));
					i--;
				} else {
					Reject(sink, body[i], "expected 'case _:' or '_ => _'");
					break;
				}
			}
			return pairs;
		}

		static bool CaptureGroup(ref int c, ref int p, VList<LNode> cArgs, VList<LNode> pArgs, ref MMap<Symbol, LNode> captures, ref VList<LNode> attrs)
		{
			Debug.Assert(IsParamsCapture(pArgs[p]));
			// The goal now is to find a sequence of nodes in cArgs that matches
			// the sequence pArgs[p+1 .. p+x] where x is the maximum value such
			// that none of the nodes in the sequence are $(params caps).
			int saved_p = p, saved_c = c;
			var savedCaptures = captures.AsImmutable();
			var savedAttrs = attrs;
			int captureSize = 0;
			for (;; captureSize++) {
				for (p++, c += captureSize; ; c++, p++) {
					// If we run out of pArgs, great, we're done; if we run out 
					// of cArgs, the match fails, unless all remaining pArgs are 
					// $(params caps).
					if (p >= pArgs.Count || IsParamsCapture(pArgs[p])) {
						goto done_group;
					} else {
						if (c >= cArgs.Count)
							return false;
						if (!MatchesPatternNested(cArgs[c], pArgs[p], ref captures, ref attrs))
							goto continue_group;
					}
				}
				continue_group:;
				p = saved_p;
				c = saved_c;
				attrs = savedAttrs;
				captures = savedCaptures.AsMutable();
			}
		done_group:
			AddCapture(captures, pArgs[saved_p], cArgs.Slice(saved_c, captureSize));
			return true;
		}

		/// <summary>Given the contents of case statement like `matchCode` or 
		/// `switch`, this method gets a list of the cases.</summary>
		/// <returns>The first item in each pair is a list of the cases associated
		/// with a single handler (for `default:`, the list is empty). The second 
		/// item is the handler code.</returns>
		static internal VList<Pair<VList<LNode>, VList<LNode>>> GetCases(VList<LNode> body, IMessageSink sink)
		{
			var pairs = VList<Pair<VList<LNode>, VList<LNode>>>.Empty;
			for (int i = 0; i < body.Count; i++)
			{
				bool isDefault;
				if (body[i].Calls(S.Lambda, 2))
				{
					var alts = body[i][0].WithoutOuterParens().AsList(S.Tuple).SmartSelect(AutoStripBraces);
					pairs.Add(Pair.Create(alts, body[i][1].AsList(S.Braces)));
				} else
				if ((isDefault = IsDefaultLabel(body[i])) || body[i].CallsMin(S.Case, 1))
				{
					var alts = isDefault ? VList<LNode>.Empty : body[i].Args.SmartSelect(AutoStripBraces);
					int bodyStart = ++i;
					for (; i < body.Count && !IsDefaultLabel(body[i]) && !body[i].CallsMin(S.Case, 1); i++) { }
					var handler = new VList<LNode>(body.Slice(bodyStart, i - bodyStart));
					pairs.Add(Pair.Create(alts, handler));
					i--;	// counteract i++ when loop repeats (redo)
				} else
				{
					Reject(sink, body[i], "expected 'case _:' or '_ => _'");
					break;
				}
			}
			return pairs;
		}