6a808492c1
* python/spot/impl.i, python/spot/__init__.py: Implement it. * NEWS: Mention it. * tests/python/atva16-fig2a.ipynb, tests/python/atva16-fig2b.ipynb, tests/python/formulas.ipynb, tests/python/ltsmin-dve.ipynb, tests/python/ltsmin-pml.ipynb, tests/python/stutter-inv.ipynb, doc/org/tut02.org: Modernize.
154 lines
4.4 KiB
Org Mode
154 lines
4.4 KiB
Org Mode
# -*- coding: utf-8 -*-
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#+TITLE: Relabeling Formulas
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#+DESCRIPTION: Code example for relabeling formulas in Spot
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#+SETUPFILE: setup.org
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#+HTML_LINK_UP: tut.html
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The task is to read an LTL formula, relabel all (possibly
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double-quoted) atomic propositions, and provide =#define= statements
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for each of these renamings, writing everything in Spin's syntax.
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* Shell
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#+BEGIN_SRC sh :results verbatim :exports both
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ltlfilt -ps --relabel=pnn --define -f '"Proc@Here" U ("var > 10" | "var < 4")'
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#+END_SRC
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#+RESULTS:
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: #define p0 (Proc@Here)
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: #define p1 (var < 4)
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: #define p2 (var > 10)
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: (p0) U ((p1) || (p2))
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When is this output interesting, you may ask? It is useful for
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instance if you want to call =ltl2ba= (or any other LTL-to-Büchi
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translator) using a formula with complex atomic propositions it cannot
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parse. Then you can pass the rewritten formula to =ltl2ba=, and
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prepend all those =#define= to its output. For instance:
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#+BEGIN_SRC sh :results verbatim :exports both
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ltlfilt -ps --relabel=pnn --define=tmp.defs -f '"Proc@Here" U ("var > 10" | "var < 4")' >tmp.ltl
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cat tmp.defs; ltl2ba -F tmp.ltl
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rm tmp.defs tmp.ltl
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#+END_SRC
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#+RESULTS:
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#+begin_example
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#define p0 (Proc@Here)
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#define p1 (var < 4)
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#define p2 (var > 10)
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never { /* (p0) U ((p1) || (p2))
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*/
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T0_init:
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if
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:: (p0) -> goto T0_init
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:: (p1) || (p2) -> goto accept_all
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fi;
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accept_all:
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skip
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}
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#+end_example
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Aside: another way to work around syntax limitations of tools is to
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use [[file:ltldo.org][=ltldo=]]. On the above example, =ltldo ltl2ba -f '"Proc@Here" U
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("var > 10" | "var < 4")' -s= would produce a never clam with the
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correct atomic proposition, even though =ltl2ba= cannot parse them.
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* Python
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The =spot.relabel= function takes an optional third parameter that
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should be a =relabeling_map=. If supplied, this map is filled with
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pairs of atomic propositions of the form (new-name, old-name).
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#+BEGIN_SRC python :results output :exports both
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import spot
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m = spot.relabeling_map()
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g = spot.relabel('"Proc@Here" U ("var > 10" | "var < 4")', spot.Pnn, m)
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for newname, oldname in m.items():
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print("#define {} ({})".format(newname.to_str(), oldname.to_str('spin', True)))
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print(g.to_str('spin', True))
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#+END_SRC
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#+RESULTS:
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: #define p0 (Proc@Here)
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: #define p1 (var < 4)
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: #define p2 (var > 10)
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: (p0) U ((p1) || (p2))
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* C++
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The =spot::relabeling_map= is just implemented as a =std::map=.
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#+BEGIN_SRC C++ :results verbatim :exports both
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#include <string>
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#include <iostream>
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#include <spot/tl/parse.hh>
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#include <spot/tl/print.hh>
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#include <spot/tl/relabel.hh>
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int main()
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{
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std::string input = "\"Proc@Here\" U (\"var > 10\" | \"var < 4\")";
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spot::parsed_formula pf = spot::parse_infix_psl(input);
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if (pf.format_errors(std::cerr))
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return 1;
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spot::formula f = pf.f;
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spot::relabeling_map m;
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f = spot::relabel(f, spot::Pnn, &m);
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for (auto& i: m)
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{
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std::cout << "#define " << i.first << " (";
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print_spin_ltl(std::cout, i.second, true) << ")\n";
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}
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print_spin_ltl(std::cout, f, true) << '\n';
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return 0;
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}
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#+END_SRC
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#+RESULTS:
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: #define p0 (Proc@Here)
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: #define p1 (var < 4)
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: #define p2 (var > 10)
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: (p0) U ((p1) || (p2))
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* Additional comments
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** Two ways to name atomic propositions
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Instead of =--relabel=pnn= (or =spot.Pnn=, or =spot::Pnn=), you can
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actually use =--relabel=abc= (or =spot.Abc=, or =spot::Abc=) to have
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the atomic propositions named =a=, =b=, =c=, etc.
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** Relabeling Boolean sub-expressions
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Instead of relabeling each atomic proposition, you could decide to
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relabel each Boolean sub-expression:
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#+BEGIN_SRC sh :results verbatim :exports both
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ltlfilt -ps --relabel-bool=pnn --define -f '"Proc@Here" U ("var > 10" | "var < 4")'
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#+END_SRC
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#+RESULTS:
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: #define p0 (Proc@Here)
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: #define p1 ((var < 4) || (var > 10))
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: (p0) U (p1)
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The relabeling routine is smart enough to not give different names
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to Boolean expressions that have some sub-expression in common.
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For instance =a U (a & b)= will not be relabeled into =(p0) U (p1)=
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because that would hide the fact that both =p0= and =p1= check for
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=a=. Instead we get this:
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#+BEGIN_SRC sh :results verbatim :exports both
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ltlfilt -ps --relabel-bool=pnn --define -f 'a U (a & b)'
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#+END_SRC
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#+RESULTS:
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: #define p0 (a)
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: #define p1 (b)
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: (p0) U ((p0) && (p1))
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This "Boolean sub-expression" relabeling is available in Python and
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C++ via the =relabel_bse= function. The interface is identical to
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=relabel=.
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