On Dec 9, 2009, at 16:51 , Bas van Dijk wrote:

I will change the types to:

stdin :: Handle ReadMode
stdout :: Handle WriteMode
stderr :: Handle WriteMode

Or are there scenarios where people want to write to stdin or read
from stdout or stderr?

These situations *do* come up; the controlling terminal for a program is open read/write on all 3 file descriptors initially, ands programs like more/less/pg rely on this and do their I/O on stdout.  Additionally, on *BSD pipes are actually socketpairs and therefore bidirectional, and a small number of programs rely on this.