feat(zig/fib): index stdin with no args

Signed-off-by: Roman Volosatovs <[email protected]>

Zig/fibonacci/src/main.zig

@@ -5,15 +5,37 @@ fn fibonacci(i: u64) u64 {
     return fibonacci(i - 1) + fibonacci(i - 2);
 }
 
+fn print_fibonacci(w: anytype, s: []const u8) !void {
+    const i = try std.fmt.parseUnsigned(u64, s, 10);
+    try w.print("Fibonacci sequence number at index {d} is {d}\n", .{i, fibonacci(i)});
+}
+
 pub fn main() !void {
     const alloc: std.mem.Allocator = std.heap.page_allocator;
 
     var args = try std.process.argsAlloc(alloc);
     defer alloc.free(args);
 
-    const stdout = std.io.getStdOut().writer();
-    for (args[1..]) |arg| {
-        const i = try std.fmt.parseUnsigned(u64, arg, 10);
-        try stdout.print("Fibonacci sequence number at index {d} is {d}\n", .{i, fibonacci(i)});
+    const stdout = std.io.getStdOut();
+    defer stdout.close();
+
+    const out = stdout.writer();
+    const indexes = args[1..];
+    if (indexes.len > 0) {
+        for (indexes) |arg| {
+            try print_fibonacci(out, arg);
+        }
+    } else {
+        const stdin = std.io.getStdIn();
+        defer stdin.close();
+
+        try out.print("No arguments specified, please specify Fibonacci sequence index: \n", .{});
+        var buf: [19]u8 = undefined;
+        if (try stdin.reader().readUntilDelimiterOrEof(&buf, '\n')) |arg| {
+            try print_fibonacci(out, arg);
+        } else {
+            std.debug.print("failed to read from stdin", .{});
+            std.process.exit(1);
+        }
     }
 }