private static Dictionary <Symbol, LNode> ScanForVariables(LNode code)
{
var nameTable = new Dictionary <Symbol, LNode>();
code.ReplaceRecursive(n =>
{
if (n.IsId)
{
nameTable[n.Name] = n;
}
else
{
LNode id = LNodeExt.GetCaptureIdentifier(n);
if (id != null)
{
if (!nameTable.ContainsKey(n.Name))
{
nameTable[id.Name] = n;
}
return(n);
}
}
return(null);
});
return(nameTable);
}
private static void DoDeconstruct(LNode arg, IMacroContext context, bool printErrorOnFailure)
{
LNode patternSpec = arg.Args[0, LNode.Missing], input = arg.Args[1, LNode.Missing];
if (!arg.Calls(S.Assign, 2))
{
if (arg.Calls(S.Lambda, 2))
{
G.Swap(ref patternSpec, ref input);
}
else
{
context.Sink.Error(arg, "expected an assignment (`patterns = input`)");
return;
}
}
// Build list of patterns out of the binary operator series p1 | p2 | p3
var patterns = new FVList <LNode>();
while (patternSpec.Calls(S.OrBits, 2) && !patternSpec.IsParenthesizedExpr())
{
patterns.Add(patternSpec[1]);
patternSpec = patternSpec[0];
}
patterns.Add(patternSpec);
// Remove outer braces, then run macros
patterns = patterns.SmartSelect(p => p.Calls(S.Braces, 1) ? p[0] : p);
input = input.Calls(S.Braces, 1) ? input[0] : input;
input = context.PreProcess(input);
// Perform matching & capturing
foreach (var pattern in patterns)
{
IDictionary <Symbol, LNode> captures;
if (LNodeExt.MatchesPattern(input, pattern, out captures))
{
if (captures.Count == 0)
{
context.Write(printErrorOnFailure ? Severity.Warning : Severity.Error, pattern,
"This pattern has no effect, since it does not use `$` to capture any variables.");
}
SetSyntaxVariables(captures, context);
return;
}
}
if (printErrorOnFailure)
{
context.Sink.Error(arg, "Deconstruction failed.");
}
}
public static LNode staticMatches(LNode node, IMacroContext context)
{
if (node.ArgCount != 2)
{
return(null);
}
LNode candidate = context.PreProcess(UnwrapBraces(node[0]));
LNode pattern = UnwrapBraces(node[1]);
MMap <Symbol, LNode> captures = new MMap <Symbol, LNode>();
if (LNodeExt.MatchesPattern(candidate, pattern, ref captures, out LNodeList _))
{
SetSyntaxVariables(captures, context);
return(F.True);
}
return(F.False);
}
public static LNode static_matchCode(LNode node, IMacroContext context)
{
if (node.AttrNamed(S.Static) == null && !node.HasSpecialName)
{
return(null); // handled by normal matchCode macro
}
var args_body = context.GetArgsAndBody(false);
VList <LNode> args = args_body.Item1, body = args_body.Item2;
if (args.Count != 1)
{
return(Reject(context, args[1], "Expected only one expression to match"));
}
var expression = context.PreProcess(AutoStripBraces(args[0]));
var cases = GetCases(body, context.Sink);
// The `default:` case is represented by an empty list of patterns.
if (cases.WithoutLast(1).Any(pair => pair.Key.IsEmpty))
{
context.Write(Severity.Error, node, "The `default:` case must be the last one, because the cases are tested in the order they appear, so no case after `default:` can be matched.");
}
MMap <Symbol, LNode> captures = new MMap <Symbol, LNode>();
foreach (Pair <VList <LNode>, VList <LNode> > pair in cases)
{
var patterns = pair.Key.IsEmpty ? new VList <LNode>((LNode)null) : pair.Key;
foreach (var pattern in patterns)
{
captures.Clear();
VList <LNode> _;
if (pattern == null || LNodeExt.MatchesPattern(expression, pattern, ref captures, out _))
{
captures[_hash] = expression; // define $#
captures.Remove(__);
return(ReplaceCaptures(pair.Value.AsLNode(S.Splice), captures));
}
}
}
return(F.Call(S.Splice)); // none of the cases matched
}
static LNode TryReplaceHere(LNode node, LNode pattern, LNode replacement, MMap <Symbol, LNode> captures, Pair <LNode, LNode>[] allPatterns)
{
if (LNodeExt.MatchesPattern(node, pattern, ref captures, out LNodeList attrs))
{
foreach (var pair in captures)
{
var input = pair.Value.AsList(S.Splice);
int c;
var output = Replace(input, allPatterns, out c);
if (output != input)
{
captures[pair.Key] = output.AsLNode(S.Splice);
}
}
return(ReplaceCaptures(replacement, captures).PlusAttrs(attrs));
}
return(null);
}
/// <summary>Finds capture variables like <c>$x</c> and replaces them with values
/// from <c>captures</c> (e.g. <c>captures[(Symbol)"x"]</c> for <c>$x</c>)</summary>
public static LNode ReplaceCaptures(LNode outputSpec, MMap <Symbol, LNode> captures)
{
if (captures.Count != 0)
{
// TODO: EXPAND SPLICES! Generally it works anyway though because
// the macro processor has built-in support for #splice.
return(outputSpec.ReplaceRecursive(n => {
LNode id, cap;
if ((id = LNodeExt.GetCaptureIdentifier(n)) != null)
{
if (captures.TryGetValue(id.Name, out cap))
{
return cap;
}
}
return null;
}));
}
return(outputSpec);
}
public static LNode replace(LNode node, IMacroContext context)
{
var args_body = context.GetArgsAndBody(true);
var args = args_body.A;
var body = args_body.B;
if (args.Count == 1 && args[0].Calls(S.Tuple))
{
args = args[0].Args; // LESv2
}
if (args.Count >= 1)
{
bool preprocess = node.Calls("replacePP");
var patterns = new Pair <LNode, LNode> [args.Count];
for (int i = 0; i < patterns.Length; i++)
{
var pair = args[i];
if (pair.Calls(S.Lambda, 2))
{
LNode pattern = pair[0], repl = pair[1];
if (preprocess)
{
pattern = context.PreProcess(pattern);
repl = context.PreProcess(repl);
}
if (pattern.Calls(S.Braces))
{
if (pattern.ArgCount == 1)
{
pattern = pattern.Args[0];
}
else
{
context.Write(Severity.Error, pattern, "The braces must contain only a single statement. To search for braces literally, use `{{ ... }}`");
}
}
if (repl.Calls(S.Braces))
{
repl = repl.Args.AsLNode(S.Splice);
}
// Avoid StackOverflowException when pattern is $Id (sadly, it
// is uncatchable so it can crash LeMP.exe and even Visual Studio)
if (LNodeExt.GetCaptureIdentifier(pattern) != null)
{
return(Reject(context, pattern, "The left side of `=>` cannot be a capture. Remove the `$`."));
}
patterns[i] = Pair.Create(pattern, repl);
}
else
{
string msg = "Expected 'pattern => replacement'.";
if (pair.Descendants().Any(n => n.Calls(S.Lambda, 2)))
{
msg += " " + "(Using '=>' already? Put the pattern on the left-hand side in parentheses.)";
}
return(Reject(context, pair, msg));
}
}
int replacementCount;
var output = Replace(body, patterns, out replacementCount);
if (replacementCount == 0)
{
context.Sink.Warning(node, "No patterns recognized; no replacements were made.");
}
return(output.AsLNode(S.Splice));
}
return(null);
}
