Window join

wj [w; c; t; (q; (f0;c0); (f1;c1))]
wj1[w; c; t; (q; (f0;c0); (f1;c1))]

Where

• t and q are simple tables to be joined (q should be sorted `sym`time with `p# on sym)
• w is a pair of lists of times/timestamps, begin and end
• c are the names of the common columns, syms and times, which must have integral types
• f0, f1 are aggregation functions applied to values in q columns c0,c1 over the intervals

returns for each record in t, a record with additional columns c0 and c1, which are the results of the aggregation functions applied to values over the matching intervals in w.

Typically this might be:

wj[w;`sym`time;trade;(quote;(max;`ask);(min;`bid))]

A quote is understood to be in existence until the next quote.