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Hide default case shorthands for Grammar to check for empty grammars

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This commit is contained in:
Suzanne Soy 2020-08-26 00:19:11 +00:00
parent 31dbe188f0
commit 139ed61fcd
2 changed files with 23 additions and 16 deletions
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37
MixFix.cs
View File

@ -15,29 +15,36 @@ using static MixFix.Fixity;
public static partial class MixFix { public static partial class MixFix {
public partial class Grammar { public partial class Grammar {
public static Grammar Sequence(params Grammar[] xs) { public static Grammar Sequence(params Grammar[] xs)
var filteredXs = xs.Where(x => !x.IsEmpty); => Sequence(xs.ToImmutableList());
if (filteredXs.Count() == 1) {
return filteredXs.Single().ElseThrow(() => new Exception("TODO: use an either to prove that this is safe."));
} else {
return Grammar.Sequence(filteredXs);
}
}
public static Grammar Or(params Grammar[] xs) public static Grammar Or(params Grammar[] xs)
=> OrCleaned(xs.ToImmutableList()); => Or(xs.ToImmutableList());
// TODO: instead hide the default constructor for Or. public static Grammar Sequence(IEnumerable<Grammar> xs) {
public static Grammar OrCleaned(IEnumerable<Grammar> xs) {
var filteredXs = xs.Where(x => !x.IsEmpty); var filteredXs = xs.Where(x => !x.IsEmpty);
if (filteredXs.Count() == 1) { if (filteredXs.Count() == 1) {
return filteredXs.Single().ElseThrow(() => new Exception("TODO: use an either to prove that this is safe.")); return filteredXs.Single().ElseThrow(() => new Exception("TODO: use an either to prove that this is safe."));
} else { } else {
return Grammar.Or(filteredXs); return new Grammar.Cases.Sequence(filteredXs);
} }
} }
public static Grammar Empty = Or(); public static Grammar Or(IEnumerable<Grammar> xs) {
var filteredXs = xs.Where(x => !x.IsEmpty);
if (filteredXs.Count() == 1) {
return filteredXs.Single().ElseThrow(() => new Exception("TODO: use an either to prove that this is safe."));
} else {
return new Grammar.Cases.Or(filteredXs);
}
}
public static Grammar RepeatOnePlus(Grammar g)
=> g.IsEmpty
? Grammar.Empty
: new Grammar.Cases.RepeatOnePlus(g);
public static Grammar Empty = new Grammar.Cases.Or();
public bool IsEmpty { public bool IsEmpty {
get => this.Match( get => this.Match(
@ -310,7 +317,7 @@ public static partial class MixFix {
parts: parts.ToImmutableList())); parts: parts.ToImmutableList()));
public static Grammar ToGrammar(this Hole precedenceGroups) public static Grammar ToGrammar(this Hole precedenceGroups)
=> Grammar.OrCleaned( => Grammar.Or(
precedenceGroups.Select(precedenceGroup => precedenceGroups.Select(precedenceGroup =>
Grammar.Rule(precedenceGroup))); Grammar.Rule(precedenceGroup)));
@ -324,7 +331,7 @@ public static partial class MixFix {
@operator.internalParts.Select(part => part.ToGrammar())); @operator.internalParts.Select(part => part.ToGrammar()));
public static Grammar ToGrammar(this IEnumerable<Operator> operators) public static Grammar ToGrammar(this IEnumerable<Operator> operators)
=> Grammar.OrCleaned( => Grammar.Or(
operators.Select(@operator => @operator.ToGrammar())); operators.Select(@operator => @operator.ToGrammar()));
public static Grammar ToGrammar(this DAGNode node) { public static Grammar ToGrammar(this DAGNode node) {

2
T4/VariantGenerator.cs
View File

@ -40,7 +40,7 @@ public static class VariantGenerator {
var Ty = @case.Value; var Ty = @case.Value;
w($" public static {name} {C}{Ty == null w($" public static {name} {C}{Ty == null
? $" = new Cases.{C}()" ? $" = new Cases.{C}()"
: $"({Ty} value) => new Cases.{C}(value)"};"); : $"({Ty} value, params Immutable.Uninstantiatable[] _) => new Cases.{C}(value)"};");
} }
} }