Sync

Task/Generator-Exponential/D/generator-exponential-1.d

@@ -1,61 +1,8 @@
-import std.stdio, std.bigint, std.range, std.algorithm;
-
-struct Filtered(R1, R2) if (is(ElementType!R1 == ElementType!R2)) {
-    R1 s1;
-    R2 s2;
-    alias ElementType!R1 T;
-    T current, source, filter;
-
-    this(R1 r1, R2 r2) {
-        s1 = r1;
-        s2 = r2;
-        source = s1.front();
-        filter = s2.front();
-        _next();
-    }
-
-    const bool empty = false;
-    @property T front() { return current; }
-    void popFront() { _next(); }
-
-    private void _next() {
-        while (true) {
-            if (source > filter) {
-                s2.popFront();
-                filter = s2.front();
-                continue;
-            } else if (source < filter) {
-                current = source;
-                s1.popFront();
-                source = s1.front();
-                break;
-            }
-            s1.popFront();
-            source = s1.front();
-        }
-    }
-}
-
-auto filtered(R1, R2)(R1 r1, R2 r2)
-if (is(ElementType!R1 == ElementType!R2)) {
-    return Filtered!(R1, R2)(r1, r2);
-}
-
-struct Count(T) {
-    T n;
-    const bool empty = false;
-    @property T front() { return n; }
-    void popFront() { /* n++; */ n += 1; }
-}
-
-Count!T count(T)(T start) { return Count!T(start); }
-Count!T count(T)() { return Count!T(cast(T)0); }
-
 void main() {
-    auto squares = count!BigInt().map!q{a ^^ 2}();
-    auto cubes = count!BigInt().map!q{a ^^ 3}();
-    auto f = filtered(squares, cubes);
+    import std.stdio, std.bigint, std.range, std.algorithm;
 
-    popFrontN(f, 20);
-    writeln(take(f, 10));
+    auto squares = 0.sequence!"n".map!(i => i.BigInt ^^ 2);
+    auto cubes = 0.sequence!"n".map!(i => i.BigInt ^^ 3);
+
+    squares.setDifference(cubes).drop(20).take(10).writeln;
 }

Task/Generator-Exponential/D/generator-exponential-2.d

@@ -1,33 +1,12 @@
-import std.stdio, std.traits;
-
-auto powers(in double e) pure nothrow {
-    double i = 0.0;
-    return () => i++ ^^ e;
-}
-
-auto filter(D)(D af, D bf) if (isCallable!D) {
-    double a = af(), b = bf();
-    return {
-        double r;
-        while (true) {
-            if (a < b) {
-                r = a;
-                a = af();
-                break;
-            }
-            if (b == a)
-                a = af();
-            b = bf();
-        }
-        return r;
-    };
-}
-
 void main() {
-    auto fgen = filter(powers(2), powers(3));
-    foreach (i; 0 .. 20)
-        fgen();
-    foreach (i; 0 .. 10)
-        write(fgen(), " ");
-    writeln();
+    import std.stdio, std.bigint, std.range, std.algorithm;
+
+    auto squares = 0.sequence!"n".map!(i => i.BigInt ^^ 2);
+    auto cubes = 0.sequence!"n".map!(i => i.BigInt ^^ 3);
+
+    squares
+    .filter!(s => cubes.find!(c => c >= s).front != s)
+    .drop(20)
+    .take(10)
+    .writeln;
 }

Task/Generator-Exponential/D/generator-exponential-3.d

@@ -0,0 +1,47 @@
+import std.stdio, std.bigint, std.range, std.algorithm;
+
+struct Filtered(R1, R2) if (is(ElementType!R1 == ElementType!R2)) {
+    R1 s1;
+    R2 s2;
+    alias ElementType!R1 T;
+    T front, source, filter;
+
+    this(R1 r1, R2 r2) {
+        s1 = r1;
+        s2 = r2;
+        source = s1.front;
+        filter = s2.front;
+        popFront;
+    }
+
+    static immutable empty = false;
+
+    void popFront() {
+        while (true) {
+            if (source > filter) {
+                s2.popFront;
+                filter = s2.front;
+                continue;
+            } else if (source < filter) {
+                front = source;
+                s1.popFront;
+                source = s1.front;
+                break;
+            }
+            s1.popFront;
+            source = s1.front;
+        }
+    }
+}
+
+auto filtered(R1, R2)(R1 r1, R2 r2) // Helper function.
+if (isInputRange!R1 && isInputRange!R2 &&
+    is(ElementType!R1 == ElementType!R2)) {
+    return Filtered!(R1, R2)(r1, r2);
+}
+
+void main() {
+    auto squares = 0.sequence!"n".map!(i => i.BigInt ^^ 2);
+    auto cubes = 0.sequence!"n".map!(i => i.BigInt ^^ 3);
+    filtered(squares, cubes).drop(20).take(10).writeln;
+}

Task/Generator-Exponential/D/generator-exponential-4.d

@@ -0,0 +1,34 @@
+import std.stdio;
+
+auto powers(in double e) pure nothrow {
+    double i = 0;
+    return () => i++ ^^ e;
+}
+
+auto filter2(D)(D af, D bf) {
+    double a = af(), b = bf();
+
+    return {
+        double r;
+        while (true) {
+            if (a < b) {
+                r = a;
+                a = af();
+                break;
+            }
+            if (b == a)
+                a = af();
+            b = bf();
+        }
+        return r;
+    };
+}
+
+void main() {
+    auto fgen = filter2(2.powers, 3.powers);
+    foreach (immutable i; 0 .. 20)
+        fgen();
+    foreach (immutable i; 0 .. 10)
+        write(fgen(), " ");
+    writeln;
+}