An lvalue is an expression the refers to an object,
and every lvalue comes with a set of attributes that can be accessed
by Yoix programs by appending an
@
and an attribute name to the lvalue.
Most of the attributes can currently only be applied to readable objects, however
access
and
name
always work, even when the object is not readable.
The names of the attributes associated with every lvalue are:
| access |
An
int
indicating the access permissions of the object.
| | growable |
An
int
that is non-zero if the object's
length
can be increased by at least one element.
| | length |
An
int
indicating the total length of a pointer object regardless of the
position of the offset pointer.
See also
offset
and
sizeof,
below.
It is zero when not applicable.
| | major |
An
int
indicating the object type.
If the object is a pointer, a stream or some similar object, then
the
minor
attribute may be needed to fully ascertain the type of the object.
| | minor |
An
int
indicating the object sub-type, if applicable.
| | nameof |
A
String
indicating the name that is associated with the object.
| | offset |
An
int
indicating the position of the offset pointer within the pointer object.
| | sizeof |
An
int
indicating the length of the pointer object starting from the
offset pointer.
| | typename |
A
String
indicating the object's type.
|
Its usage description can be summarized as follows:
Attribute:
LValue @ access
LValue @ length
LValue @ major
LValue @ minor
LValue @ nameof
LValue @ offset
LValue @ sizeof
LValue @ typename
| |
| Example: |
The program,
import yoix.io.*;
import yoix.stdio.*;
import yoix.string.*;
String str = "hello";
String ptr = str;
const String cstr = str;
final String fstr = strdup(str);
modes(mode) {
String md = "";
if((mode&LOCK) == LOCK)
md += "L";
else md += "_";
if((mode&READ) == READ)
md += "R";
else md += "_";
if((mode&WRITE) == WRITE)
md += "W";
else md += "_";
if((mode&EXECUTE) == EXECUTE)
md += "X";
else md += "_";
return(md);
}
deflag(flag) {
String perms = "";
perms = modes(flag&(READ|WRITE|LOCK|EXECUTE));
perms += "->";
perms += modes((flag>>4)&(READ|WRITE|LOCK|EXECUTE));
return(perms);
}
ptr++;
printf("The %s variable %s (%d/%d) with value '%s' has:\n\
\taccess: %d (%s)\n\tlength: %d\n\toffset: %d\n\tsizeof: %d\n",
str@typename, str@nameof, str@major, str@minor, str,
str@access, deflag(str@access),
str@length, str@offset, str@sizeof);
printf("The %s variable %s (%d/%d) with value '%s' has:\n\
\taccess: %d (%s)\n\tlength: %d\n\toffset: %d\n\tsizeof: %d\n",
ptr@typename, ptr@nameof, ptr@major, ptr@minor, ptr,
ptr@access, deflag(ptr@access),
ptr@length, ptr@offset, ptr@sizeof);
printf("The %s variable %s (%d/%d) with value '%s' has:\n\
\taccess: %d (%s)\n\tlength: %d\n\toffset: %d\n\tsizeof: %d\n",
cstr@typename, cstr@nameof, cstr@major, cstr@minor, cstr,
cstr@access, deflag(cstr@access),
cstr@length, cstr@offset, cstr@sizeof);
printf("The %s variable %s (%d/%d) with value '%s' has:\n\
\taccess: %d (%s)\n\tlength: %d\n\toffset: %d\n\tsizeof: %d\n",
fstr@typename, fstr@nameof, fstr@major, fstr@minor, fstr,
fstr@access, deflag(fstr@access),
fstr@length, fstr@offset, fstr@sizeof);
prints something like,
The String variable str (180/191) with value 'hello' has:
access: 118 (_RW_->_RWX)
length: 5
offset: 0
sizeof: 5
The String variable ptr (180/191) with value 'ello' has:
access: 118 (_RW_->_RWX)
length: 5
offset: 1
sizeof: 4
The String variable cstr (180/191) with value 'hello' has:
access: 125 (LR_X->_RWX)
length: 5
offset: 0
sizeof: 5
The String variable fstr (180/191) with value 'hello' has:
access: 221 (LR_X->LR_X)
length: 5
offset: 0
sizeof: 5
on standard output.
| | |
| See Also: |
const,
final,
Object,
Pointer,
reference
|
|
