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\subsection{objectname}
\label{labobjectname}
\noindent Name: \textbf{objectname}\\
\phantom{aaa}returns, given a \sollya object, a string that can be reparsed to the object\\[0.2cm]
\noindent Library name:\\
\verb| sollya_obj_t sollya_lib_objectname(sollya_obj_t);|\\[0.2cm]
\noindent Usage:
\begin{center}
\textbf{objectname}(\emph{obj}) : \textsf{any type} $\rightarrow$ \textsf{string}\\
\end{center}
\noindent Description: \begin{itemize}
\item \textbf{objectname}(\emph{obj}) queries the \sollya symbol table in order to recover the
name of an identifier the object \emph{obj} is assigned to. If it succeeds, it
returns a string containing the recovered identifier. In contrast, if it
does not succeed, it returns a string simply containing a textual
representation of~\emph{obj}.
\item The only condition for an identifier to be eligible to be returned by
\textbf{objectname}(\emph{obj}) is to be accessible in the scope \textbf{objectname} is executed in,
\emph{i.e.}, not to be shadowed by an identifier of the same name which does not
hold the object \emph{obj}.
\item In any case, if the string returned by \textbf{objectname} is given to the \textbf{parse}
command in the same scope, the original object \emph{obj} is recovered.
\item \textbf{objectname} is particularly useful in combination with \textbf{getbacktrace}, when
the \sollya procedure stack is to be displayed in a fashion, where
procedures are identified by their name and not their procedural content.
\item \textbf{objectname} may also be used to get a string representation of the free
mathematical variable.
\item If an object is simply to be cast into a string, without trying to
retrieve an identifier for it, \textbf{objectname} is not appropriate. In this case,
it suffices to concatenate it to an empty string with the \textbf{@} operator.
\end{itemize}
\noindent Example 1:
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> s = "Hello";
> objectname("Hello");
s
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 2:
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> f = exp(x);
> g = sin(x);
> [| objectname(exp(x)), objectname(sin(x)), objectname(cos(x)) |];
[|"f", "g", "cos(x)"|]
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 3:
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> o = { .f = exp(x), .I = [-1;1] };
> s1 = o@""; s1;
{ .f = exp(x), .I = [-1;1] }
> s2 = objectname({ .I = [-1;1], .f = exp(x)}); s2;
o
> parse(s1) == parse(s2);
true
> write("s2 = \"", s2, "\" parses to ", parse(s2), "\n");
s2 = "o" parses to { .f = exp(x), .I = [-1;1] }
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 4:
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> n = 1664;
> objectname(n);
n
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 5:
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> f = exp(x);
> g = sin(x);
> procedure test() {
var f;
var h;
f = tan(x);
h = cos(x);
[| objectname(exp(x)), objectname(sin(x)), objectname(cos(x)), objectname(
tan(x)) |];
};
> test();
[|"exp(x)", "g", "h", "f"|]
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 6:
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> procedure apply_proc(p, a, b) {
return p(a, b);
};
> procedure show_trace_and_add(n, m) {
var i, bt;
bt = getbacktrace();
write("Procedure stack:\n");
for i from 0 to length(bt) - 1 do {
write(" Procedure ", objectname((bt[i]).called_proc), " called with
", length((bt[i]).passed_args), " arguments\n");
};
write("\n");
return n + m;
};
> procedure show_and_succ(u) {
return apply_proc(show_trace_and_add, u, 1);
};
> show_and_succ(16);
Procedure stack:
Procedure show_trace_and_add called with 2 arguments
Procedure apply_proc called with 3 arguments
Procedure show_and_succ called with 1 arguments
17
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 7:
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> f = exp(three_decker_sauerkraut_and_toadstool_sandwich_with_arsenic_sauce);
> g = sin(_x_);
> h = f(g);
> h;
exp(sin(three_decker_sauerkraut_and_toadstool_sandwich_with_arsenic_sauce))
> objectname(_x_);
three_decker_sauerkraut_and_toadstool_sandwich_with_arsenic_sauce
\end{Verbatim}
\end{minipage}\end{center}
See also: \textbf{parse} (\ref{labparse}), \textbf{var} (\ref{labvar}), \textbf{getbacktrace} (\ref{labgetbacktrace}), \textbf{proc} (\ref{labproc}), \textbf{procedure} (\ref{labprocedure}), \textbf{@} (\ref{labconcat})
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