starting.tex 11.8 KB
Newer Older
MARCHE Claude's avatar
MARCHE Claude committed
1
\chapter{Getting Started}
MARCHE Claude's avatar
MARCHE Claude committed
2
\label{chap:starting}
MARCHE Claude's avatar
MARCHE Claude committed
3

MARCHE Claude's avatar
MARCHE Claude committed
4
5
\section{Hello Proofs}

MARCHE Claude's avatar
MARCHE Claude committed
6
The first and basic step in using \why is to write a suitable input
MARCHE Claude's avatar
MARCHE Claude committed
7
8
file. When one wants to learn a programming language, you start by
writing a basic program. Here we start by writing a file containing a
9
basic set of goals.
MARCHE Claude's avatar
MARCHE Claude committed
10

MARCHE Claude's avatar
MARCHE Claude committed
11
Here is our first \why file, which is the file
MARCHE Claude's avatar
MARCHE Claude committed
12
\texttt{examples/hello\_proof.why} of the distribution.
13
14
15
\verbatiminput{../examples/hello_proof.why}

Any declaration must occur
MARCHE Claude's avatar
MARCHE Claude committed
16
17
18
19
inside a theory, which is in that example called TheoryProof and
labelled with a comment inside double quotes. It contains three goals
named $G_1,G_2,G_3$. The first two are basic propositional goals,
whereas the third involves some integer arithmetic, and thus it
MARCHE Claude's avatar
MARCHE Claude committed
20
requires to import the theory of integer arithmetic from the \why
MARCHE Claude's avatar
MARCHE Claude committed
21
22
23
24
standard library, which is done by the \texttt{use} declaration above.

We don't give more details here about the syntax and refer to
Chapter~\ref{chap:syntax} for detailed explanations. In the following,
MARCHE Claude's avatar
MARCHE Claude committed
25
we show how this file is handled in the \why GUI
MARCHE Claude's avatar
MARCHE Claude committed
26
(Section~\ref{sec:gui}) then in batch mode using the \texttt{why3}
27
executable (Section~\ref{sec:batch}).
MARCHE Claude's avatar
MARCHE Claude committed
28
29
30
31


\section{Getting Started with the GUI}
\label{sec:gui}
MARCHE Claude's avatar
MARCHE Claude committed
32
33
34
35
36
37

The graphical interface allows to browse into a file or a set of
files, and check the validity of goals with external provers, in a
friendly way. This section presents the basic use of this GUI. Please
refer to Section~\ref{sec:ideref} for a more complete description.

MARCHE Claude's avatar
MARCHE Claude committed
38
\begin{figure}[tbp]
MARCHE Claude's avatar
MARCHE Claude committed
39
  \includegraphics[width=\textwidth]{gui-0-70-1.png}
MARCHE Claude's avatar
MARCHE Claude committed
40
41
42
43
44
45
46
47
48
  \caption{The GUI when started the very first time}
  \label{fig:gui1}
\end{figure}

The GUI is launched on the file above as follows.
\begin{verbatim}
why3ide hello_proof.why
\end{verbatim}
When the GUI is started for the first time, you should get a window
49
which looks like the screenshot of Figure~\ref{fig:gui1}.
50
51
52
53
54
55
56
57
58
59

The left column is a tool bar which provides different actions to
apply on goals. The section ``Provers'' displays the provers that were
detected as installed on your computer\footnote{If not done yet, you
  must perform prover autodetection using \texttt{why3config
    --detect-provers}}. Three provers were detected, in this case
these are Alt-Ergo~\cite{ergo}, Coq~\cite{CoqArt} and
Simplify~\cite{simplify05}.

The middle part is a tree view that
60
allows to browse inside the theories.
61
62
63
64
65
% Initially, the item of this tree
% are closed. We can expand this view using the menu \textsf{View/Expand
%   all} or its shortcut \textsf{Ctrl-E}. This will result is something
% like the screenshot of Figure~\ref{fig:gui2}.
In this tree view, we have a structured view of the file: this file
66
contains one theory, itself containg three goals.
67

MARCHE Claude's avatar
MARCHE Claude committed
68
69

\begin{figure}[tbp]
70
71
 \includegraphics[width=\textwidth]{gui-0-70-2.png}
  \caption{The GUI with goal G1 selected}
MARCHE Claude's avatar
MARCHE Claude committed
72
73
  \label{fig:gui2}
\end{figure}
74
In Figure~\ref{fig:gui2}, we clicked on the row corresponding to
MARCHE Claude's avatar
MARCHE Claude committed
75
76
77
78
79
goal $G_1$. The \emph{task} associated with this goal is then
displayed on the top right, and the corresponding part of the input
file is shown on the bottom right part.


80
81
\subsection{Calling provers on goals}

MARCHE Claude's avatar
MARCHE Claude committed
82
83
You are now ready to call these provers on the goals. Whenever you
click on a prover button, this prover is called on the goal selected
84
in the tree view. You can select several goals at a time, either
MARCHE Claude's avatar
MARCHE Claude committed
85
86
87
88
89
90
91
by using multi-selection (typically by clicking while pressing the
\textsf{Shift} or \textsf{Ctrl} key) or by selecting the parent theory
or the parent file. Let us now select the theory ``HelloProof'' and
click on the \textsf{Simplify} button. After a short time, you should
get the display of Figure~\ref{fig:gui3}.

\begin{figure}[tbp]
MARCHE Claude's avatar
MARCHE Claude committed
92
\includegraphics[width=\textwidth]{gui-0-70-3.png}
MARCHE Claude's avatar
MARCHE Claude committed
93
94
95
96
  \caption{The GUI after Simplify prover is run on each goal}
  \label{fig:gui3}
\end{figure}

MARCHE Claude's avatar
MARCHE Claude committed
97
98
99
100
The goal $G_1$ is now marked with a green ``checked'' icon in the
status column. This means that the goal is proved by the Simplify
prover. On the contrary, the two other goals are not proved, they remain
marked with an orange question mark.
101
102
103

You can immediately attempt to prove the remaining goals using another
prover, {\eg} Alt-Ergo, by clicking on the corresponding button. The
104
goal $G_3$ should be proved now, but not $G_2$.
105
106
107
108
109
110
111

\subsection{Applying transformations}

Instead of calling a prover on a goal, you can apply a transformation
to it.  Since $G_2$ is a conjunction, a possibility is to split it
into subgoals. You can do that by clicking on the \textsf{Split}
button of section ``Transformations'' of the left toolbar. Now you
MARCHE Claude's avatar
MARCHE Claude committed
112
have two subgoals, and you can try again a prover on them, for example
MARCHE Claude's avatar
MARCHE Claude committed
113
114
Simplify. We already have a lot of goals and proof attempts, so it is a good idea to close the sub-trees which are already proved: this can be done by the menu \textsf{View/Collapse proved goals}, or even better by its shortcut ``Ctrl-C''.
You should see now what is displayed on Figure~\ref{fig:gui4}.
115
116

\begin{figure}[tbp]
MARCHE Claude's avatar
MARCHE Claude committed
117
118
 \includegraphics[width=\textwidth]{gui-0-70-4.png}
  \caption{The GUI after splitting goal $G_2$ and collapsing proved goals}
119
120
121
122
123
  \label{fig:gui4}
\end{figure}

The first part of goal $G_2$ is still unproved. As a last resort, we
can try to call the Coq proof assistant. The first step is to click on
MARCHE Claude's avatar
MARCHE Claude committed
124
the \textsf{Coq} button. A new sub-row appear for Coq, and
125
126
127
128
129
unsurprisingly the goal is not proved by Coq either. What can be done
now is editing the proof: select that row and then click on the
\textsf{Edit} button in section ``Tools'' of the toolbar. This should
launch the Coq proof editor, which is \texttt{coqide} by default (see
Section~\ref{sec:ideref} for details on how to configure this). You get
MARCHE Claude's avatar
MARCHE Claude committed
130
now a regular Coq file to fill in, as shown on Figure~\ref{fig:coqide}.
131
132
Please take care of the comments of this file. Only the part between
the two last comments can be modified. Moreover, these comments
133
themselves should not be modified at all, they are used to mark the
134
part you modify, in order to regenerate the file if the goal is
135
changed.
136
137

\begin{figure}[tbp]
MARCHE Claude's avatar
MARCHE Claude committed
138
  \includegraphics[width=\textwidth]{coqide-0-70.png}
139
140
141
142
143
144
145
146
147
148
149
  \caption{CoqIDE on subgoal 1 of $G_2$}
  \label{fig:coqide}
\end{figure}

Of course, in that particular case, the goal cannot be proved since it
is not valid. The only thing to do is to fix the input file, as
explained below.

\subsection{Modifying the input}

Currently, the GUI does not allow to modify the input file. You must
MARCHE Claude's avatar
MARCHE Claude committed
150
151
152
edit the file external by some editor of your choice. Let's assume we
change the goal $G_2$ by replacing the first occurrence of true by
false, \eg
153
\begin{verbatim}
154
  goal G2 : (false -> false) /\ (true \/ false)
155
\end{verbatim}
MARCHE Claude's avatar
MARCHE Claude committed
156
We can reload the modified file in the IDE using menu \textsf{File/Reload}, or the shortcut ``Ctrl-R''. We get the tree view shown on Figure~\ref{fig:gui5}.
157
158

\begin{figure}[tbp]
MARCHE Claude's avatar
MARCHE Claude committed
159
160
  \includegraphics[width=\textwidth]{gui-0-70-5.png}
  \caption{File reloaded after modifying goal $G_2$}
161
162
163
164
  \label{fig:gui5}
\end{figure}

The important feature to notice first is that all the previous proof
MARCHE Claude's avatar
MARCHE Claude committed
165
166
167
168
169
170
attempts and transformations were saved in a database --- an XML file
created when the \why file was opened in the GUI for the first
time. Then, for all the goals that remain unchanged, the previous
proofs are shown again. For the parts that changed, the previous
proofs attempts are shown but marked with "(obsolete)" so that you
know the results are not accurate. You can now retry to prove all what
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
remains unproved using any of the provers.

\subsection{Replaying obsolete proofs}

Instead of pushing a prover's button to rerun its proofs, you can
\emph{replay} the existing but obsolete proof attempts, by clicking on
the \textsf{Replay} button. By default, \textsf{Replay} only replays
proofs that were successful before. If you want to replay all of them,
you must select the context \textsf{all goals} at the top of the left
tool bar.

Notice that replaying can be done in batch mode, using the
\texttt{why3replayer} tool (see Section~\ref{sec:why3replayer}) For
example, running the replayer on the \texttt{hello\_proof} example is
as follows (assuming $G_2$ still is \texttt{(true -> false) /\ (true
  \/ false)}).
\begin{verbatim}
$ why3replayer hello_proof
Info: found directory 'hello_proof' for the project
Opening session...[Xml warning] prolog ignored
[Reload] file '../hello_proof.why'
[Reload] theory 'HelloProof'
[Reload] transformation split_goal for goal G2
 done
Progress: 9/9
 2/3
   +--file ../hello_proof.why: 2/3
      +--theory HelloProof: 2/3
         +--goal G2 not proved
Everything OK.
\end{verbatim}
The last line tells us that no difference was detected between the
current run and the informations in the XML file. The tree above
reminds us that the G2 is not proved.
MARCHE Claude's avatar
MARCHE Claude committed
205
206
207

\subsection{Cleaning}

208
209
210
211
212
213
You may want to clean some the proof attempts, \eg removing the
unsuccessful ones when a project is finally fully proved.

A proof or a transformation can be removed by selecting it and
clicking on button \textsf{Remove}. You must confirm the
removal. Beware that there is no way to undo such a removal.
MARCHE Claude's avatar
MARCHE Claude committed
214

215
216
217
The \textsf{Clean} button performs an automatic removal of all proofs
attempts that are unsuccessful, while there exists a successful proof
attempt for the same goal.
218

MARCHE Claude's avatar
MARCHE Claude committed
219
\section{Getting Started with the \why Command}
MARCHE Claude's avatar
MARCHE Claude committed
220
221
222
223
224
\label{sec:batch}

The why3 command allows to check the validity of goals with external
provers, in batch mode. This section presents the basic use of this
tool. Refer to Section~\ref{sec:why3ref} for a more complete
MARCHE Claude's avatar
MARCHE Claude committed
225
226
227
description of this tool and all its command-line options.

The very first time you want to use Why, you should proceed with
228
autodetection of external provers. We have already seen how to do
MARCHE Claude's avatar
MARCHE Claude committed
229
it in the \why GUI. On the command line, this is done as follows
230
(here ``\texttt{>}'' is the prompt):
MARCHE Claude's avatar
MARCHE Claude committed
231
\begin{verbatim}
232
> why3config --detect
MARCHE Claude's avatar
MARCHE Claude committed
233
234
\end{verbatim}
This prints some information messages on what detections are attempted. To know which
235
provers have been successfully detected, you can do as follows.
MARCHE Claude's avatar
MARCHE Claude committed
236
237
238
239
240
241
242
243
244
\begin{verbatim}
> why3 --list-provers
Known provers:
  alt-ergo (Alt-Ergo)
  coq (Coq)
  simplify (Simplify)
\end{verbatim}
The first word of each line is a unique identifier for the associated prover. We thus
have now the three provers Alt-Ergo~\cite{ergo}, Coq~\cite{CoqArt} and
245
Simplify~\cite{simplify05}.
MARCHE Claude's avatar
MARCHE Claude committed
246
247
248

Let's assume now we want to run Simplify on the HelloProof
example. The command to type and its output are as follows, where the
249
250
\verb|-P| option is followed by the unique prover identifier (as shown
by \texttt{--list-provers} option).
MARCHE Claude's avatar
MARCHE Claude committed
251
252
253
254
255
256
\begin{verbatim}
> why3 -P simplify hello_proof.why
hello_proof.why HelloProof G1 : Valid (0.10s)
hello_proof.why HelloProof G2 : Unknown: Unknown (0.01s)
hello_proof.why HelloProof G3 : Unknown: Unknown (0.00s)
\end{verbatim}
257
258
Unlike \why GUI, the command-line tool does not save the proof attempts
or applied transformations in a database.
MARCHE Claude's avatar
MARCHE Claude committed
259

260
We can also specify which goal or goals to prove. This is done by giving
MARCHE Claude's avatar
MARCHE Claude committed
261
first a theory identifier, then goal identifier(s). Here is the way to
MARCHE Claude's avatar
MARCHE Claude committed
262
call Alt-Ergo on goals $G_2$ and $G_3$.
MARCHE Claude's avatar
MARCHE Claude committed
263
264
265
266
267
\begin{verbatim}
> why3 -P alt-ergo hello_proof.why -T HelloProof -G G2 -G G3
hello_proof.why HelloProof G2 : Unknown: Unknown (0.01s)
hello_proof.why HelloProof G3 : Valid (0.01s)
\end{verbatim}
MARCHE Claude's avatar
MARCHE Claude committed
268

MARCHE Claude's avatar
MARCHE Claude committed
269
Finally, a transformation to apply to goals before proving them can be
270
specified. To know the unique identifier associated to
271
a transformation, do as follows.
MARCHE Claude's avatar
MARCHE Claude committed
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
\begin{verbatim}
> why3 --list-transforms
Known non-splitting transformations:
  [...]

Known splitting transformations:
  [...]
  split_goal
  split_intro
\end{verbatim}
Here is how you can split the goal $G_2$ before calling
Simplify on resulting subgoals.
\begin{verbatim}
> why3 -P simplify hello_proof.why -a split_goal -T HelloProof -G G2
hello_proof.why HelloProof G2 : Unknown: Unknown (0.00s)
hello_proof.why HelloProof G2 : Valid (0.00s)
\end{verbatim}
Section~\ref{sec:transformations} gives the description of the various
transformations available.
MARCHE Claude's avatar
MARCHE Claude committed
291

MARCHE Claude's avatar
MARCHE Claude committed
292
293
294
295
296
%%% Local Variables:
%%% mode: latex
%%% TeX-PDF-mode: t
%%% TeX-master: "manual"
%%% End: