Add hasLength and isRandomAccessRange

dlang · Dec 16, 2021 · a94b148 · a94b148
1 parent 564bc56
commit a94b148
Show file tree

Hide file tree

Showing 2 changed files with 44 additions and 11 deletions.
diff --git a/std/range/primitives.d b/std/range/primitives.d
@@ -1030,7 +1030,7 @@ See_Also:
  */
 enum bool isBidirectionalRange(R) = isForwardRange!R
     && is(typeof((R r) => r.popBack))
-    && is(ReturnType!((R r) => r.back) == ElementType!R);
+    && is(ReturnType!((R r) => r.back) == ReturnType!((R r) => r.front));
 
 ///
 @safe unittest
@@ -1561,14 +1561,8 @@ characters, but instead the number of encoding units, and as such is not useful
 with range-oriented algorithms. To use strings as random-access ranges with
 length, use $(REF representation, std, string) or $(REF byCodeUnit, std, utf).
 */
-template hasLength(R)
-{
-    static if (is(typeof(((R* r) => r.length)(null)) Length))
-        enum bool hasLength = is(Length == size_t) &&
-                              !(isAutodecodableString!R && !isAggregateType!R);
-    else
-        enum bool hasLength = false;
-}
+enum bool hasLength(R) = is(typeof(((R* r) => r.length)(null)) == size_t)
+        && (!isAutodecodableString!R || isAggregateType!R);
 
 ///
 @safe unittest

diff --git a/std2xalpha/range/primitives.d b/std2xalpha/range/primitives.d
@@ -15,18 +15,21 @@ version (std_use_public_import)
 else
 {
     import v1 = std.range.primitives;
+    // Unchanged in this version.
     alias isInputRange = v1.isInputRange;
+    // TODO
     alias put = v1.put;
+    // Unchanged in this version.
     alias isOutputRange = v1.isOutputRange;
+    // Unchanged in this version.
     alias isForwardRange = v1.isForwardRange;
+    // Unchanged in this version.
     alias isBidirectionalRange = v1.isBidirectionalRange;
-    alias isRandomAccessRange = v1.isRandomAccessRange;
     alias hasMobileElements = v1.hasMobileElements;
     alias ElementEncodingType = v1.ElementEncodingType;
     alias hasSwappableElements = v1.hasSwappableElements;
     alias hasAssignableElements = v1.hasAssignableElements;
     alias hasLvalueElements = v1.hasLvalueElements;
-    alias hasLength = v1.hasLength;
     alias isInfinite = v1.isInfinite;
     alias hasSlicing = v1.hasSlicing;
     alias walkLength = v1.walkLength;
@@ -146,3 +149,39 @@ unittest
     static assert(is(ElementType!(string) == immutable char));
     static assert(is(ElementType!(dstring) == immutable(dchar)));
 }
+
+/**
+@@@TODO@@@ This alias redefines `isRandomAccessRange` for std2x. The difference is of
+course that the new `isRandomAccessRange` does not support autodecoding, so string
+types are random access ranges.
+*/
+enum bool isRandomAccessRange(R) =
+    is(typeof(imported!"std2xalpha.traits".lvalueOf!R[1]) == ElementType!R)
+    && isForwardRange!R
+    && (isBidirectionalRange!R || isInfinite!R)
+    && (hasLength!R || isInfinite!R)
+    && (isInfinite!R || !is(typeof(imported!"std2xalpha.traits".lvalueOf!R[$ - 1]))
+        || is(typeof(imported!"std2xalpha.traits".lvalueOf!R[$ - 1]) == ElementType!R))
+;
+
+///
+@safe unittest
+{
+    static assert(isForwardRange!string);
+    static assert(isBidirectionalRange!string);
+    static assert(isRandomAccessRange!string);
+}
+
+/**
+@@@TODO@@@ This redefines `hasLength` for std2x. The difference is of
+course that the new `hasLength` does not support autodecoding, so string
+types do have length, as they should.
+*/
+enum bool hasLength(R) = is(typeof(((R* r) => r.length)(null)) == size_t);
+
+///
+@safe unittest
+{
+    static assert(hasLength!string);
+    static assert(hasLength!wstring);
+}