boost/spirit
2
0
Fork 0
mirror of https://github.com/boostorg/spirit.git synced 2026-01-19 04:42:11 +00:00
Code Issues Projects Releases Wiki Activity

added x3 example of wrapping multiple attributes using std::tuple

Browse Source
This commit is contained in:
ttan
2019-06-18 14:54:03 +08:00
parent 96cfe50992
commit d3ab9a709e
3 changed files with 61 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
doc/x3/abstracts/attributes.qbk
View File

@@ -86,18 +86,10 @@ attribute:
x3::space, // delimiter grammar
p); // attribute to fill while parsing
[tip *For sequences only:* __x3__ exposes a set of API functions
usable mainly with sequences. Very much like the functions of the `scanf`
and `printf` families these functions allow to pass the attributes for
each of the elements of the sequence separately. Using the corresponding
overload of /X3's/ parse function, the expression above
could be rewritten as:
``
double d1 = 0.0, d2 = 0.0;
x3::phrase_parse(begin, end, x3::double_ >> x3::double_, x3::space, d1, d2);
``
where the first attribute is used for the first `double_`, and
the second attribute is used for the second `double_`.
[tip *For sequences only:* To keep it simple, unlike __Spirit.qi__, __x3__ does
not support more than one attribute anymore in the `parse` and `phrase_parse` function.
Just use `std:tuple'. Be sure to include `boost/fusion/adapted/std_tuple.hpp' in this case.
]
[heading The Attribute of Alternative Parsers]
@@ -156,14 +148,10 @@ handling their variable parts. In this context you can think about __x3__'s
primitive components (such as the `double_` above) as of being
type safe placeholders for the attribute values.
[tip Similarly to the tip provided above, this example could be rewritten
using /Spirit's/ multi-attribute API function:
``
double d1 = 0.0, d2 = 0.0;
x3::parse(begin, end, '(' >> x3::double_ >> ", " >> x3::double_ >> ')', d1, d2);
``
which provides a clear and comfortable syntax, more similar to the
placeholder based syntax as exposed by `printf` or `boost::format`.
[tip *For sequences only:* To keep it simple, unlike __Spirit.qi__, __x3__ does
not support more than one attribute anymore in the `parse` and `phrase_parse` function.
Just use `std:tuple'. Be sure to include `boost/fusion/adapted/std_tuple.hpp' in this case.
]
Let's take a look at this from a more formal perspective: