.TH LIBNORMALFORM_VARIABLE 3 LIBNORMALFORM
.SH NAME
libnormalform_variable \- Boolean variable

.SH SYNOPSIS
.nf
#include <libnormalform.h>

enum libnormalform_value {
        \fILIBNORMALFORM_FALSE\fP = 0,
        \fILIBNORMALFORM_TRUE\fP = 1
};

struct libnormalform_variable {
        enum libnormalform_value \fIvalue\fP;
        void *\fIuser_data\fP;
        const char *\fIidentifier;
        struct libnormalform_variable *\fIcopy_for_clone\fP;
};

LIBNORMALFORM_SENTENCE *libnormalform_variable(struct libnormalform_variable *\fIvariable\fP);
.fi
.PP
Link with
.IR -lnormalform .

.SH DESCRIPTION
The
.BR libnormalform_variable ()
function creates a sentence object out
of an application-managed variable.
.PP
.I variable->value
is used only be the
.BR libnormalform_evaluate (3)
function and must be set to either
.I LIBNORMALFORM_FALSE
or
.I LIBNORMALFORM_TRUE
before the
.BR libnormalform_evaluate (3)
function is called, to let the
function know what value the
variable has for that specific
call to the
.BR libnormalform_evaluate (3)
function.
.PP
See
.BR libnormalform_to_string (3)
for the purpose of
.IR variable->identifier ,
it need not be set before the
.BR libnormalform_to_string (3)
function is called.
.PP
See
.BR libnormalform_clone (3)
for the purpose of
.IR variable->copy_for_clone ,
it need not be set before the
.BR libnormalform_clone (3)
function is called.
.PP
The application can set
.I variable->user_data
set freely, and can opt to leave it
unset. It is never used or reference
by the library, but it could be used
by the application to identify the
variable.
.PP
.I variable
must not be
.IR NULL .
.PP
The returned pointer shall either be
deallocated with the
.BR libnormalform_free (3)
function or be relinquished by being
used as part of another sentence.

.SH RETURN VALUE
Upon successful completion, the
.BR libnormalform_variable ()
function returns an sentence object of
the variable; otherwise, the function
returns
.I NULL
and sets
.I errno
to indicate the error.

.SH ERRORS
The
.BR libnormalform_variable ()
function fails if:
.TP
.B ENOMEM
Insufficient memory was available to
create the sentence object.

.SH ATTRIBUTES
For an explanation of the terms used in this
section, see
.BR attributes (7)
and
.IR "info \(dq(libc)POSIX Safety Concepts\(dq" .
.TS
allbox;
lb lb lb
l l l.
Interface	Attribute	Value
T{
.BR libnormalform_variable ()
T}	Thread safety	MT-Safe
T{
.BR libnormalform_variable ()
T}	Async-signal safety	AS-Unsafe heap
T{
.BR libnormalform_variable ()
T}	Async-cancel safety	AC-Safe mem, AC-Unsafe heap
.TE

.SH SEE ALSO
.BR libnormalform (7),
.BR libnormalform_function (3)