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Fix the associativity of ->, <->, U, R, W, and M wrt the PSL standard.

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* src/ltlparse/ltlparse.yy: Make all the above operators
right-associative.  Also let `:' have precedence over `;'.
* src/ltltest/reduccmp.test: Adjust for the `:' precedence.
* doc/tl/tl.tex, NEWS: Document this.
This commit is contained in:
Alexandre Duret-Lutz 2012-04-28 16:13:24 +02:00
parent 807dcefba4
commit ce437cd499
4 changed files with 43 additions and 45 deletions
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4
NEWS
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@ -36,7 +36,9 @@ New in spot 0.8.3a:
configured and built. This helps on systems (such as MinGW)
where LBTT cannot be built. The test-suite will skip any
LBTT-based test if LBTT is missing.
* Interface chances:
* Interface changes:
- Operators ->, <->, U, W, R, and M are no parsed as
right-associative to better match the PSL standard.
- The new entry point for LTL/PSL simplifications is the function
ltl_simplifier::simplify() declared in src/ltlvisit/simplify.hh.
The ltl_simplifier class implements a cache.

47
doc/tl/tl.tex
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@ -873,40 +873,24 @@ operator, even if the operator has multiple synonyms (like \samp{|},
\section{Operator precedence}
\spottodo[inline]{The following operator precedence describe the
current parser of Spot, but this is not what we want eventually.
For instance $\IMPLIES$ should be right associative. $\U$ and $\W$
would probably make more sense as right associative operators too.\\
%
Tools that have $\U$, $\R$, $\W$, and $\M$ operators as left
associative: Spin, ltl2ba (same parser as spin), Wring, psl2ba,
Spot, Modella, NuSMV.\\
%
Tools (and doc) that have these operators as right associative: Goal
(hence Büchi Store), PSL reference manual, LTL2AUT, LTL2Büchi (from
JavaPathFinder).\\
%
Tools that have these operators as non-associative (parentheses are
required): Vis, LBTT.\\
%
While compiling these lists I have also discovered that not all
people aggreed on the associativity of $\IMPLIES$ and $\EQUIV$.
Some have both left-assoc, or both right-assoc, other have only
$\IMPLIES$ as right-assoc.\\
%
We want to get closer to the PSL standard eventually.}
The following operator precedence describes the current parser of
Spot. It has not always been this way. Especially, all operators
were left associative until version 0.9, when we changed the
associativity of $\IMPLIES$, $\EQUIV$, $\U$, $\R$, $\W$, and $\M$ to get closer
to the PSL standard~\cite{psl.04.lrm,eisner.06.psl}.
\begin{center}
\begin{tabular}{clc}
assoc. & operators & priority \\
\midrule
left & $\Asuffix,\,\AsuffixEQ,\,\Esuffix,\,\EsuffixEQ$ & \tikz[remember picture,baseline]\node (lowest){lowest}; \\
left & $\CONCAT,\,\FUSION$ & \\
left & $\IMPLIES,\,\EQUIV$ & \\
right & $\Asuffix,\,\AsuffixEQ,\,\Esuffix,\,\EsuffixEQ$ & \tikz[remember picture,baseline]\node (lowest){lowest}; \\
left & $\CONCAT$ & \\
left & $\FUSION$ & \\
right & $\IMPLIES,\,\EQUIV$ & \\
left & $\XOR$ & \\
left & $\OR$ & \\
left & $\AND,\,\ANDALT$ & \\
left & $\U,\,\W,\,\M,\,\R$ & \\
right & $\U,\,\W,\,\M,\,\R$ & \\
& $\F,\,\G$ & \\
& $\X$ & \\
& $\STAR{\mvar{i}..\mvar{j}},\,\PLUS,\,\EQUAL{\mvar{i}..\mvar{j}},\,\GOTO{\mvar{i}..\mvar{j}}$ & \\
@ -918,6 +902,17 @@ left & $\U,\,\W,\,\M,\,\R$
\draw[->] (lowest) -- (highest);
\end{tikzpicture}
Beware that not all tools agree on the associativity of these
operators. For instance Spin, ltl2ba (same parser as spin), Wring,
psl2ba, Modella, and NuSMV all have $\U$ and $\R$ as left-associative,
while Goal (hence Büchi store), LTL2AUT, and LTL2Büchi (from
JavaPathFinder) have $\U$ and $\R$ as right-associative. Vis and LBTT
have these two operators as non-associative (parentheses required).
Similarly the tools do not aggree on the associativity of $\IMPLIES$
and $\EQUIV$: some tools handle both operators as left-associative, or
both right-associative, other have only $\IMPLIES$ as right-associative.
\chapter{Properties}
When Spot builds a formula (represented by an AST with shared

11
src/ltlparse/ltlparse.yy
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@ -111,19 +111,20 @@ using namespace spot::ltl;
/* Priorities. */
/* Low priority regex operator. */
%left OP_UCONCAT OP_ECONCAT OP_UCONCAT_NONO OP_ECONCAT_NONO
/* Low priority SERE-LTL binding operator. */
%right OP_UCONCAT OP_ECONCAT OP_UCONCAT_NONO OP_ECONCAT_NONO
%left OP_CONCAT OP_FUSION
%left OP_CONCAT
%left OP_FUSION
/* Logical operators. */
%left OP_IMPLIES OP_EQUIV
%right OP_IMPLIES OP_EQUIV
%left OP_OR
%left OP_XOR
%left OP_AND OP_SHORT_AND
/* LTL operators. */
%left OP_U OP_R OP_M OP_W
%right OP_U OP_R OP_M OP_W
%nonassoc OP_F OP_G
%nonassoc OP_X

8
src/ltltest/reduccmp.test
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@ -263,13 +263,13 @@ for x in ../reduccmp ../reductaustr; do
run 0 $x '{a && b && d[->2..4]} <>-> d' '0'
run 0 $x '{a && { c* : b* : (g|h)*}} <>-> d' 'a & c & b & (g | h) & d'
run 0 $x '{a && {b;c}} <>-> d' '0'
run 0 $x '{a && {b;c:e}} <>-> d' '0'
run 0 $x '{a && {(b;c):e}} <>-> d' '0'
run 0 $x '{a && {b*;c*}} <>-> d' '{a && {b*|c*}} <>-> d' # until better
run 0 $x '{a && {b*;c*:e}} <>-> d' '{a && {b*|c*} && e} <>-> d' # idem
run 0 $x '{a && {(b*;c*):e}} <>-> d' '{a && {b*|c*} && e} <>-> d' # idem
run 0 $x '{a && {b*;c}} <>-> d' 'a & c & d'
run 0 $x '{a && {b*;c:e}} <>-> d' 'a & c & d & e'
run 0 $x '{a && {(b*;c):e}} <>-> d' 'a & c & d & e'
run 0 $x '{a && {b;c*}} <>-> d' 'a & b & d'
run 0 $x '{a && {b;c*:e}} <>-> d' 'a & b & d & e'
run 0 $x '{a && {(b;c*):e}} <>-> d' 'a & b & d & e'
run 0 $x '{{{b1;r1*}&&{b2;r2*}};c}' 'b1&b2&X{{r1*&&r2*};c}'
run 0 $x '{{b1:r1*}&&{b2:r2*}}' '{{b1&&b2}:{r1*&&r2*}}'
run 0 $x '{{r1*;b1}&&{r2*;b2}}' '{{r1*&&r2*};{b1&&b2}}'