Single Table Report With Calculated Column

I've read some on table partitioning and using nested select statements
with group by, but have not found the syntax to produce the needed results.

From a table I extract row counts grouped by three columns:

select stream, sampdate, func_feed_grp, count(*) from benthos group
by stream, sampdate, func_feed_grp order by stream, sampdate,
func_feed_group;

And I want to include the proportion of each count based on the total rows
for each stream and sampdate. The totals are obtained with this statement:

select stream, sampdate, count(*) as tot_cnt from benthos group by stream,
sampdate order by stream, sampdate;

What I do not know how to do is combine the two so the resulting table
contains the columns stream, sampdate, count, proportion. I want to learn
how to build the sub-select to get this result. Joe Celko's 'SQL for
Smarties, 4th Ed.' has a close example in the chapter on table partitioning,
but I could not apply that model to my table.

TIA,

Rich