[pcstl]

~ does indeed denote named arguments. To call a function named f which has an argument named arg with arg set to the value x, the syntax is:

    f ~arg:x

[gpderetta]

But what about ~buf here:

  let len = Core.In_channel.input in_ch ~buf ~pos:0 ~len:buf_size

[test9753]

~buf is shorthand for ~buf:buf

[gpderetta]

Oh, nice.