public static bool Matches <T1>([NotNull] this IStructure structure, [CanBeNull] out T1 obj1)
where T1 : ZilObject
{
if (structure.HasLength(1) && structure.GetFirst() is T1 elem1)
{
obj1 = elem1;
return(true);
}
obj1 = default;
return(false);
}
static ZilObject PerformMember(Context ctx, [NotNull] ZilObject needle, [NotNull] IStructure haystack,
[NotNull] Func <ZilObject, ZilObject, bool> equality)
{
while (haystack != null && !haystack.IsEmpty)
{
if (equality(needle, haystack.GetFirst()))
{
return((ZilObject)haystack);
}
haystack = haystack.GetRest(1);
}
return(ctx.FALSE);
}
static bool CheckElements([NotNull] Context ctx, [NotNull] IStructure structure,
[NotNull] ZilListoidBase elements, bool segment, bool ignoreErrors)
{
foreach (var subpattern in elements)
{
ZilObject first;
if (subpattern is ZilVector vector)
{
var len = vector.GetLength();
if (len > 0 && vector[0] is ZilAtom atom)
{
int i;
// ReSharper disable once SwitchStatementMissingSomeCases
switch (atom.StdAtom)
{
case StdAtom.REST:
i = 1;
while (!structure.IsEmpty)
{
first = structure.GetFirst();
Debug.Assert(first != null);
if (!Check(ctx, first, vector[i]))
{
return(false);
}
i++;
if (i >= len)
{
i = 1;
}
structure = structure.GetRest(1);
Debug.Assert(structure != null);
}
// !<FOO [REST A B C]> must repeat A B C a whole number of times
// (ZILF extension)
if (segment && i != 1)
{
return(false);
}
return(true);
case StdAtom.OPT:
case StdAtom.OPTIONAL:
// greedily match OPT elements until the structure ends or a match fails
for (i = 1; i < len; i++)
{
if (structure.IsEmpty)
{
break;
}
first = structure.GetFirst();
Debug.Assert(first != null);
if (!Check(ctx, first, vector[i]))
{
break;
}
structure = structure.GetRest(1);
Debug.Assert(structure != null);
}
// move on to the next subpattern, if any
continue;
}
}
else if (len > 0 && vector[0] is ZilFix fix)
{
var count = fix.Value;
for (int i = 0; i < count; i++)
{
for (int j = 1; j < vector.GetLength(); j++)
{
if (structure.IsEmpty)
{
return(false);
}
first = structure.GetFirst();
Debug.Assert(first != null);
if (!Check(ctx, first, vector[j]))
{
return(false);
}
structure = structure.GetRest(1);
Debug.Assert(structure != null);
}
}
// move on to the next subpattern, if any
continue;
}
if (ignoreErrors)
{
return(false);
}
throw new InterpreterError(
InterpreterMessages.Unrecognized_0_1,
"vector in DECL pattern",
vector.ToStringContext(ctx, false));
}
if (structure.IsEmpty)
{
return(false);
}
first = structure.GetFirst();
Debug.Assert(first != null);
if (!Check(ctx, first, subpattern))
{
return(false);
}
structure = structure.GetRest(1);
Debug.Assert(structure != null);
}
return(!segment || structure.IsEmpty);
}
