Add exponential Histogram

Fixes open-telemetry#2421

delve_commands.rst

@@ -0,0 +1,27 @@
+Run a single test, set break:
+
+ocelotl@hilleman:~/github/lightstep/otel-launcher-go/lightstep/sdk/metric/aggregator/histogram/structure$ dlv test -- -test.run TestAlternatingGrowth1
+Type 'help' for list of commands.
+(dlv) break tryIncrement
+Breakpoint 1 set at 0x68d100,0x68d900,0x68e100,0x68f5e6,0x68f9e6,0x68fde6,0x6901e6,0x68e8e0 for github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/aggregator/histogram/structure.(*bucketsVarwidth).tryIncrement() <autogenerated>:1
+(dlv) c
+> github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/aggregator/histogram/structure.(*bucketsVarwidth[uint8]).tryIncrement() <autogenerated>:1 (hits goroutine(6):1 total:1) (PC: 0x68f5e6)
+(dlv) l
+> github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/aggregator/histogram/structure.(*bucketsVarwidth[uint8]).tryIncrement() <autogenerated>:1 (hits goroutine(6):1 total:1) (PC: 0x68f5e6)
+Command failed: open <autogenerated>: no such file or directory
+(dlv) n
+> github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/aggregator/histogram/structure.(*bucketsVarwidth[go.shape.uint8_0]).tryIncrement() ./exponential.go:684 (hits goroutine(6):2 total:2) (PC: 0x68d100)
+   679:         tmp := b.counts[src]
+   680:         b.counts[src] = 0
+   681:         return uint64(tmp)
+   682: }
+   683:
+=> 684: func (b *bucketsVarwidth[N]) tryIncrement(bucketIndex int32, incr uint64) bool {
+   685:         var limit = uint64(N(0) - 1)
+   686:         if uint64(b.counts[bucketIndex])+incr <= limit {
+   687:                 b.counts[bucketIndex] += N(incr)
+   688:                 return true
+   689:         }
+(dlv) print b.counts
+[]uint8 len: 1, cap: 1, [0]
+(dlv) 

iee_754.rst

@@ -0,0 +1,13 @@
+IEE 754
+=======
+
+
+A *normalized* number is written in *scientific notation* with one non-zero
+decimal digit before the decimal point.
+
+The binary representation of a normalized number will always have its first bit
+set to 1. To avoid spending space in this bit, it is implicit.
+
+IEE 754 double precision numbers are represented like this:
+
+1-sign-bit 11-exponent-bits 52-significand-bits for a total of 64 bits.