As of 0.15.X, you can build strings using a std.Io.Writer. You can either: - use std.Io.Writer.fixed to use a slice for the memory, and use .buffered() when yo

As of 0.15.X, you can build strings using a std.Io.Writer. You can either: - use std.Io.Writer.fixed to use a slice for the memory, and use .buffered() when you're done to get the subslice of the buffer that contains your string or - Create an instance of std.Io.Writer.Allocating with an allocator, and use .toOwnedSlice() when you're done to get your allocated string. In both cases you just use regular print functions to build your string. Depending on your needs, it may also be good to use a fixed writer with a dynamically allocated slice, where the size of the allocation is computed using std.fmt.count(). This can be better than using std.Io.Writer.Allocating because you can avoid doing multiple allocations.