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;
 }