fix an issue in findSegment

src/hncore/Digraph.zig

@@ -1,7 +1,7 @@
 const std = @import("std");
 
-/// A data type to store relations of nodes in directional-graph.
-pub fn Digraph(comptime T: type) type {
+/// A data type to store connections of nodes in directional-graph.
+pub fn Digraph(comptime T: type, comptime lessThanFn: LessThanFunc(T)) type {
     return struct {
         const Node     = T;
         const Conn     = struct { from: T, to: T, };
@@ -14,16 +14,16 @@ pub fn Digraph(comptime T: type) type {
         map: ConnList,
 
         ///
-        pub fn init(alloc: std.mem.Allocator, map_unsorted: []const Conn) !@This() {
-            var map_sorted = ConnList.init(alloc);
-            try map_sorted.ensureTotalCapacity(map_unsorted.len);
-            for (map_unsorted) |conn| {
-                try map_sorted.append(conn);
+        pub fn init(alloc: std.mem.Allocator, mapUnsorted: []const Conn) !@This() {
+            var mapSorted = ConnList.init(alloc);
+            try mapSorted.ensureTotalCapacity(mapUnsorted.len);
+            for (mapUnsorted) |conn| {
+                try mapSorted.append(conn);
             }
-            std.mem.sort(Conn, map_sorted.items, {}, compare_conn);
+            std.mem.sort(Conn, mapSorted.items, {}, compareConn);
 
             return .{
-                .map  = map_sorted,
+                .map  = mapSorted,
             };
         }
         ///
@@ -32,47 +32,53 @@ pub fn Digraph(comptime T: type) type {
         }
 
         ///
-        pub fn connect_if(self: *@This(), from: T, to: T) !bool {
-            const begin, const end = self.find_segment(from);
-            if (self.find_connection_in_segment(from, to, begin, end)) |_| {
+        pub fn connectIf(self: *@This(), from: T, to: T) !bool {
+            const begin, const end = self.findSegment(from);
+            if (self.findConnectionInSegment(from, to, begin, end)) |_| {
                 return false;
             } else {
                 try self.map.insert(end, Conn { .from = from, .to = to, });
                 return true;
             }
         }
-        /// Same to `connect_if`, but returns an error if it's already connected.
+        /// Same to `connectIf`, but returns an error if it's already connected.
         pub fn connect(self: *@This(), from: T, to: T) !void {
-            if (!try self.connect_if(from, to)) {
+            if (!try self.connectIf(from, to)) {
                 return Error.AlreadyConnected;
             }
         }
 
         ///
-        pub fn disconnect_if(self: *@This(), from: T, to: T) bool {
-            const begin, const end = self.find_segment(from);
-            if (self.find_connection_in_segment(from, to, begin, end)) |idx| {
+        pub fn disconnectIf(self: *@This(), from: T, to: T) bool {
+            const begin, const end = self.findSegment(from);
+            if (self.findConnectionInSegment(from, to, begin, end)) |idx| {
                 _ = self.map.orderedRemove(idx);
                 return true;
             } else {
                 return false;
             }
         }
-        /// Same to `disconnect_if`, but returns an error if it's not connected.
+        /// Same to `disconnectIf`, but returns an error if it's not connected.
         pub fn disconnect(self: *@This(), from: T, to: T) !void {
-            if (!self.disconnect_if(from, to)) {
+            if (!self.disconnectIf(from, to)) {
                 return Error.NotConnected;
             }
         }
 
         ///
-        pub fn is_connected(self: *const @This(), from: T, to: T) bool {
-            const begin, const end = self.find_segment(from);
-            return self.find_connection_in_segment(from, to, begin, end) != null;
+        pub fn isConnected(self: *const @This(), from: T, to: T) bool {
+            const begin, const end = self.findSegment(from);
+            return self.findConnectionInSegment(from, to, begin, end) != null;
 
         }
 
-        fn find_connection_in_segment(self: *const @This(), from: T, to: T, begin: usize, end: usize) ?usize {
+        ///
+        pub fn getChildrenOf(self: *const @This(), from: T) []const Conn {
+            const begin, const end = self.findSegment(from);
+            return self.map.items[begin..end];
+        }
+
+        fn findConnectionInSegment(self: *const @This(), from: T, to: T, begin: usize, end: usize) ?usize {
             for (self.map.items[begin..end], begin..) |v, idx| {
                 if ((v.from == from) and (v.to == to)) {
                     return idx;
@@ -80,36 +86,36 @@ pub fn Digraph(comptime T: type) type {
             }
             return null;
         }
-        fn find_segment(self: *const @This(), from: T) struct { usize, usize } {
+        fn findSegment(self: *const @This(), from: T) struct { usize, usize } {
             const n = self.map.items.len;
             if (n == 0) {
                 return .{ 0, 0, };
             }
 
-            const base_idx  = self.binsearch(from).?;
-            const base_from = self.map.items[base_idx].from;
+            const baseIdx  = self.binsearch(from).?;
+            const baseFrom = self.map.items[baseIdx].from;
 
             var begin: usize = undefined;
             var end  : usize = undefined;
-            if (base_from < from) {
-                begin = base_idx;
-                while ((begin < n) and (self.map.items[begin].from != from)) { begin += 1; }
+            if (baseFrom < from) {
+                begin = baseIdx;
+                while ((begin < n) and (self.map.items[begin].from < from)) { begin += 1; }
 
                 end = begin;
                 while ((end < n) and (self.map.items[end].from == from)) { end += 1; }
 
-            } else if (base_from > from) {
-                end = base_idx;
-                while ((end > 0) and (self.map.items[end-1].from != from)) { end -= 1; }
+            } else if (baseFrom > from) {
+                end = baseIdx;
+                while ((end > 0) and (self.map.items[end-1].from > from)) { end -= 1; }
 
                 begin = end;
                 while ((begin > 0) and (self.map.items[begin-1].from == from)) { begin -= 1; }
 
             } else {
-                begin = base_idx;
+                begin = baseIdx;
                 while ((begin > 0) and (self.map.items[begin-1].from == from)) { begin -= 1; }
 
-                end = base_idx;
+                end = baseIdx;
                 while ((end < n) and (self.map.items[end].from == from)) { end += 1; }
             }
             return .{ begin, end, };
@@ -137,14 +143,40 @@ pub fn Digraph(comptime T: type) type {
             }
             return idx;
         }
-        fn compare_conn(_: void, a: Conn, b: Conn) bool {
-            return a.from < b.from;
+        fn compareConn(_: void, a: Conn, b: Conn) bool {
+            return lessThanFn(a.from, b.from);
         }
     };
 }
 
+/// A type of comparator function for the type T, which is to be passed as an argument of `Digraph()`.
+pub fn LessThanFunc(comptime T: type) type {
+    return fn (lhs: T, rhs: T) bool;
+}
+
+/// Returns a lessThanFunc for the comparable type T.
+pub fn lessThanFuncFor(comptime T: type) LessThanFunc(T) {
+    return struct {
+        fn inner(lhs: T, rhs: T) bool {
+            if (@typeInfo(T) == .pointer) {
+                return @intFromPtr(lhs) < @intFromPtr(rhs);
+            } else {
+                return lhs < rhs;
+            }
+        }
+    }.inner;
+}
+
+test "compile check for various types" {
+    _ = Digraph(u8,  lessThanFuncFor(u8));
+    _ = Digraph(u16, lessThanFuncFor(u16));
+    _ = Digraph(i8,  lessThanFuncFor(i8));
+    _ = Digraph(i16, lessThanFuncFor(i16));
+    _ = Digraph(*i8, lessThanFuncFor(*i8));
+    _ = Digraph(*anyopaque, lessThanFuncFor(*anyopaque));
+}
 test "check if connected" {
-    const Sut = Digraph(u8);
+    const Sut = Digraph(u8, lessThanFuncFor(u8));
 
     const map = [_]Sut.Conn {
         .{ .from = 3, .to = 0, },
@@ -155,39 +187,39 @@ test "check if connected" {
     var sut = try Sut.init(std.testing.allocator, map[0..]);
     defer sut.deinit();
 
-    try std.testing.expect(sut.is_connected(0, 1));
-    try std.testing.expect(!sut.is_connected(1, 0));
+    try std.testing.expect(sut.isConnected(0, 1));
+    try std.testing.expect(!sut.isConnected(1, 0));
 
-    try std.testing.expect(sut.is_connected(1, 3));
-    try std.testing.expect(!sut.is_connected(3, 1));
+    try std.testing.expect(sut.isConnected(1, 3));
+    try std.testing.expect(!sut.isConnected(3, 1));
 
-    try std.testing.expect(sut.is_connected(3, 0));
-    try std.testing.expect(!sut.is_connected(0, 3));
+    try std.testing.expect(sut.isConnected(3, 0));
+    try std.testing.expect(!sut.isConnected(0, 3));
 
-    try std.testing.expect(!sut.is_connected(0, 2));
-    try std.testing.expect(!sut.is_connected(2, 0));
+    try std.testing.expect(!sut.isConnected(0, 2));
+    try std.testing.expect(!sut.isConnected(2, 0));
 
-    try std.testing.expect(!sut.is_connected(1, 2));
-    try std.testing.expect(!sut.is_connected(2, 1));
+    try std.testing.expect(!sut.isConnected(1, 2));
+    try std.testing.expect(!sut.isConnected(2, 1));
 }
 test "make new connection" {
-    const Sut = Digraph(u8);
+    const Sut = Digraph(u8, lessThanFuncFor(u8));
 
     var sut = try Sut.init(std.testing.allocator, &.{});
     defer sut.deinit();
 
-    try std.testing.expect(try sut.connect_if(2, 1));
+    try std.testing.expect(try sut.connectIf(2, 1));
 
-    try std.testing.expect(sut.is_connected(2, 1));
-    try std.testing.expect(!sut.is_connected(1, 2));
+    try std.testing.expect(sut.isConnected(2, 1));
+    try std.testing.expect(!sut.isConnected(1, 2));
 
     try sut.connect(3, 1);
 
-    try std.testing.expect(sut.is_connected(3, 1));
-    try std.testing.expect(!sut.is_connected(1, 3));
+    try std.testing.expect(sut.isConnected(3, 1));
+    try std.testing.expect(!sut.isConnected(1, 3));
 }
 test "making an existing connection fails" {
-    const Sut = Digraph(u8);
+    const Sut = Digraph(u8, lessThanFuncFor(u8));
 
     const map = [_]Sut.Conn {
         .{ .from = 0, .to = 1, },
@@ -195,11 +227,11 @@ test "making an existing connection fails" {
     var sut = try Sut.init(std.testing.allocator, map[0..]);
     defer sut.deinit();
 
-    try std.testing.expect(!try sut.connect_if(0, 1));
+    try std.testing.expect(!try sut.connectIf(0, 1));
     try std.testing.expectError(Sut.Error.AlreadyConnected, sut.connect(0, 1));
 }
 test "disconnect an existing connection" {
-    const Sut = Digraph(u8);
+    const Sut = Digraph(u8, lessThanFuncFor(u8));
 
     const map = [_]Sut.Conn {
         .{ .from = 0, .to = 1, },
@@ -208,42 +240,45 @@ test "disconnect an existing connection" {
     var sut = try Sut.init(std.testing.allocator, map[0..]);
     defer sut.deinit();
 
-    try std.testing.expect(sut.disconnect_if(0, 1));
-    try std.testing.expect(!sut.is_connected(0, 1));
+    try std.testing.expect(sut.disconnectIf(0, 1));
+    try std.testing.expect(!sut.isConnected(0, 1));
 
     try sut.disconnect(2, 3);
-    try std.testing.expect(!sut.is_connected(2, 3));
+    try std.testing.expect(!sut.isConnected(2, 3));
 }
 test "disconnecting a missing connection fails" {
-    const Sut = Digraph(u8);
+    const Sut = Digraph(u8, lessThanFuncFor(u8));
 
     var sut = try Sut.init(std.testing.allocator, &.{});
     defer sut.deinit();
 
-    try std.testing.expect(!sut.disconnect_if(0, 1));
+    try std.testing.expect(!sut.disconnectIf(0, 1));
     try std.testing.expectError(Sut.Error.NotConnected, sut.disconnect(1, 0));
 }
 test "chaotic operation" {
-    const Sut = Digraph(u16);
+    const Sut = Digraph(u16, lessThanFuncFor(u16));
 
     var sut = try Sut.init(std.testing.allocator, &.{});
     defer sut.deinit();
 
     const N = 100;
+    const P = 109;
+    const Q = 113;
+    const R = 127;
     for (0..N) |v| {
         const x: Sut.Node = @intCast(v);
-        try sut.connect(x*%7, x*%13);
+        try sut.connect((x*Q)%P, (x*R)%P);
     }
     for (N/2..N) |v| {
         const x: Sut.Node = @intCast(v);
-        try sut.disconnect(x*%7, x*%13);
+        try sut.disconnect((x*Q)%P, (x*R)%P);
     }
     for (0..N/2) |v| {
         const x: Sut.Node = @intCast(v);
-        try std.testing.expect(sut.is_connected(x*%7, x*%13));
+        try std.testing.expect(sut.isConnected((x*Q)%P, (x*R)%P));
     }
     for (N/2..N) |v| {
         const x: Sut.Node = @intCast(v);
-        try std.testing.expect(!sut.is_connected(x*%7, x*%13));
+        try std.testing.expect(!sut.isConnected((x*Q)%P, (x*R)%P));
     }
 }