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Tweak parser to require fewer parentheses around if-then-else and lambdas

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E.g. "True && if True then True else True" is now accepted without parens.
The grammar now relies on the relatively low precedence of 'else', '->',
and ':' relative to other infix operators to disambiguate parsing. This
addresses issue #74.
This commit is contained in:
Brian Huffman 2014-09-02 19:22:27 -07:00
parent 34877371f6
commit 9ed8523c68
1 changed files with 4 additions and 3 deletions
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7
src/Cryptol/Parser.y
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@ -324,13 +324,10 @@ repl :: { ReplInput }
expr :: { Expr }
: iexpr { $1 }
| iexpr ':' type { at ($1,$3) $ ETyped $1 $3 }
| 'if' ifBranches 'else' expr { at ($1,$4) $ mkIf $2 $4 }
| expr 'where' '{' '}' { at ($1,$4) $ EWhere $1 [] }
| expr 'where' '{' decls '}' { at ($1,$5) $ EWhere $1 (reverse $4) }
| expr 'where' 'v{' 'v}' { at ($1,$2) $ EWhere $1 [] }
| expr 'where' 'v{' vdecls 'v}' { at ($1,$4) $ EWhere $1 (reverse $4) }
| '\\' apats '->' expr { at ($1,$4) $ EFun (reverse $2) $4 }
ifBranches :: { [(Expr, Expr)] }
: ifBranch { [$1] }
@ -342,6 +339,10 @@ ifBranch :: { (Expr, Expr) }
iexpr :: { Expr }
: aexprs { mkEApp $1 }
| iexpr ':' type { at ($1,$3) $ ETyped $1 $3 }
| 'if' ifBranches 'else' iexpr { at ($1,$4) $ mkIf $2 $4 }
| '\\' apats '->' iexpr { at ($1,$4) $ EFun (reverse $2) $4 }
| iexpr '@' iexpr { binOp $1 (op ECAt $2) $3 }
| iexpr '@@' iexpr { binOp $1 (op ECAtRange $2) $3 }
| iexpr '!' iexpr { binOp $1 (op ECAtBack $2) $3 }