1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
|
Time resolutions (or em(units of time)) are essential components of time
specifications. Time resolutions are defined through objects of the class
hi(ratio)tt(std::ratio).
Before the class tt(ratio) can be used, the tthi(ratio) header file must be
included. Instead the tt(<chrono>) header file can be included.
The class tt(ratio) requires two em(template arguments). These are positive
integral numbers surrounded by pointed brackets defining, respectively, the
numerator and denominator of a fraction (by default the denominator equals
1). Examples:
verb( ratio<1> - representing one;
ratio<60> - representing 60
ratio<1, 1000> - representing 1/1000.)
The class tt(ratio) defines two directly accessible static data
members: tt(num)hi(ratio: num) represents its numerator, tt(den)hi(ratio: den)
its denominator. A tt(ratio) definition by itself simply defines a certain
amount. E.g., when executing the following program
verbinsert(-as4 examples/ratio.cc)
the text 1,200 is displayed, as that's the `amount' represented by
tt(ratio<5, 1000>): tt(ratio) simplifies the fraction whenever possible.
A fairly large number of predefined tt(ratio) types exist. They are, like
tt(ratio) itself, defined in the standard namespace and can be used instead of
the more cumbersome tt(ratio<x>) or tt(ratio<x, y>) specification:
tablecenter(8)(llcllcll)(
rowline()
row()
row(cell(i(yocto)) cell(10+sups(-24)) cellq()
cell(i(zepto)) cell(10+sups(-21)) cellq() cells(2)())
rowline()
row()
row(cell(i(atto)) cell(10+sups(-18)) cell()
cell(i(femto)) cell(10+sups(-15)) cell()
cell(i(pico)) cell(10+sups(-12)))
row(cell(i(nano)) cell(10+sups(-9)) cell()
cell(i(micro)) cell(10+sups(-6)) cell()
cell(i(milli)) cell(10+sups(-3)))
row(cell(i(centi)) cell(10+sups(-2)) cell()
cell(i(deci)) cell(10+sups(-1)))
rowline()
row()
row(cell(i(deca)) cell(10+sups(1)) cell()
cell(i(hecto)) cell(10+sups(2)) cell()
cell(i(kilo)) cell(10+sups(3)))
row(cell(i(mega)) cell(10+sups(6)) cell()
cell(i(giga)) cell(10+sups(9)) cell()
cell(i(tera)) cell(10+sups(12)))
row(cell(i(peta)) cell(10+sups(15)) cell()
cell(i(exa)) cell(10+sups(18)))
rowline()
row()
row(cell(i(zetta)) cell(10+sups(21)) cell()
cell(i(yotta)) cell(10+sups(24)))
rowline()
)
(em(note:) the definitions of the types tt(yocto, zepto, zetta) and tt(yotta)
use integral constants exceeding 64 bits. Although these constants are defined
in bf(C++), they are not available on 64 bit or smaller architectures.)
Time related ratios can very well be interpreted as fractions or multiple of
seconds, with tt(ratio<1, 1>) representing a resolution of one second.
Here is an example showing how these abbreviations can be used:
verbinsert(-s4 //milli examples/milli.cc)
|
