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Generator Directives Controlling Case Sensitivity (upper[], lower[])
Description

The generator directives ns::lower[] and ns::upper[] force their embedded generators to emit lower case or upper case only characters based on the interpretation of the generated characters in the character set defined by ns (see Character Encoding Namespace).

Header
// forwards to <boost/spirit/home/karma/directive/upper_lower_case.hpp>
#include <boost/spirit/include/karma_upper_lower_case.hpp>

Also, see Include Structure.

Namespace

Name

ns::lower

ns::upper

In the table above, ns represents a Character Encoding Namespace.

Model of

The model of lower[] and upper[] is the model of its subject generator.

Notation

a

A generator object

A

Attribute type of the generator a

ns

A Character Encoding Namespace.

Expression Semantics

The lower[] and upper[] directives have no special generator semantics. They are pure modifier directives. They indirectly influence the way all subject generators work. They add information (the tag::upper or tag::lower) to the Modifier template parameter used while transforming the proto::expr into the corresponding generator expression. This is achieved by the following specializations:

namespace boost { namespace spirit
{
    template <typename CharEncoding>
    struct is_modifier_directive<
            karma::domain
          , tag::char_code<tag::lower, CharEncoding> >
      : mpl::true_ 
    {};

    template <typename CharEncoding>
    struct is_modifier_directive<
            karma::domain
          , tag::char_code<tag::upper, CharEncoding> >
      : mpl::true_ 
}}

(for more details see the section describing the compilation process of the Boost.Proto expression into the corresponding generator expressions).

Expression

Semantics

ns::lower[a]

Generate a as lower case, interpreted in the character set defined by ns. The directive succeeds as long as the embedded generator succeeded (unless the underlying output stream reports an error).

ns::upper[a]

Generate a as upper case, interpreted in the character set defined by ns. The directive succeeds as long as the embedded generator succeeded (unless the underlying output stream reports an error).

[Note] Note

If both directives are 'active' with regard to a generator, the innermost of those directives takes precedence. For instance:

generate(sink, ascii::lower['A' << ascii::upper['b']])

will generate "aB" (without the quotes).

Further, the directives will have no effect on generators emitting characters not having an upper case or lower case equivalent in the character set defined by ns.

Attributes

See Compound Attribute Notation.

Expression

Attribute

ns:lower[a]

a: A --> ns:lower[a]: A
a: Unused --> ns:lower[a]: Unused

ns:upper[a]

a: A --> ns:upper[a]: A
a: Unused --> ns:upper[a]: Unused

Complexity

The overall complexity of the generator directives ns::lower[] and ns::upper[] is defined by the complexity of its embedded generators. The directives themselves are compile time only directives, having no impact on runtime performance.

Example
[Note] Note

The test harness for the example(s) below is presented in the Basics Examples section.

Some includes:

#include <boost/spirit/include/karma.hpp>
#include <iostream>
#include <string>

Some using declarations:

using boost::spirit::karma::double_;
using boost::spirit::ascii::upper;
using boost::spirit::ascii::lower;

Basic usage of the upper and lower generator directives:

test_generator_attr("abc:2.0e-06", lower["ABC:" << double_], 2e-6);
test_generator_attr("ABC:2.0E-06", upper["abc:" << double_], 2e-6);


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