FBB::A2x objects offer the C++ equivalent of the standard C
conversion functions atoi(3), atol(3), atof(3) etc. A2x
objects generalize these C functions to any type that can be extracted
from an istream object. Since FBB::A2x represents the object-variant
of the C functions, and is therefore type-safe and extensible,
their use is greatly preferred over using the standard C functions.
NAMESPACE
FBB
All constructors, members, and operators, mentioned in this
man-page, are defined in the namespace FBB.
INHERITS FROM
std::istringstream
CONSTRUCTORS
A2x():
This constructor constructs an empty A2x object. No
information can be converted from a thus constructed A2x object.
A2x(char const *text):
This constructor stores text. If text represents a textual
value of some type, the A2x object may be used to initialize or assign
this value to a variable of that particular type. Extraction, however is also
still possible.
A2x(std::string const &str):
This constructor stores the text contained in str. If this text
represents a textual value of some type, the A2x object may be used to
initialize or assign this value to a variable of that particular
type. Extraction is also still possible.
The copy constructor is available.
STATIC MEMBER FUNCTION
bool lastFail():
This member returns true if the last conversion failed (i.e., the
object's fail() member returned true and returns false otherwise).
This member allows checks on the success of the extraction/conversion using
anonymous A2x objects. The member also returns true when no
conversions have as yet been performed.
Note that this member is a thread-unsafe static member: in a
multithreaded program locks may be required to ensure that the proper
conversion result is inspected.
MEMBER FUNCTION
All members of the istringstream class are available.
Type to():
This member returns any type Type supporting extractions from
i[string]streams. If the extraction fails, the A2x object's
good() member will return false, and the Type's default value is
returned. This operator was implemented as a template member function. There
is also a type conversion operator available (see below), but the member
function variant may be preferred over the conversion operator in situations
where explicit disambiguation is required (e.g., in cases where a
conversion has no obvious type solution such as direct insertions) An example
is provided in the EXAMPLE section below.
OVERLOADED OPERATORS
operator Type():
Conversion to any type Type supporting
extractions from i[string]streams. If the extraction fails, the A2x
object's good() member will return false, and the Type's default
value is returned. This operator was implemented as a template member
function.
istream &operator>>(istream &, Type &):
Extraction to any type Type supporting extractions from
i[string]streams. If the extraction fails, the A2x object's
good() member will return false, and the Type's default value is
returned (this facility is implied by the fact that this class inherits from
istringstream, but it's probably useful to stress that the extraction
operation is still available).
A2x &operator=(char const *):
Stores new text in the A2x object, resets the status flags to
ios::good. If a 0-pointer is passed, an empty string is stored.
A2x &operator=(std::string const &):
Stores the text stored in the std::string argument in the
A2x object, resets the status flags to ios::good.
A2x &operator=(A2x const &):
The standard overloaded assignment operator is available
EXAMPLE
int x = A2x("12");
A2x a2x("12.50");
double d;
d = a2x;
a2x = "err";
d = a2x; // d now 0
a2x = " a";
char c = a2x; // c now 'a'
// explicit conversion to `double'
cout << A2x("12.4").to<double>() << endl;