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Handle left recursion by failing again

db4
Chris Double 2008-03-29 00:49:39 +13:00
parent cca4700e49
commit 010ce80076
2 changed files with 11 additions and 8 deletions
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13
extra/peg/ebnf/ebnf-tests.factor
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@ -144,16 +144,17 @@ IN: peg.ebnf.tests
"Z" [EBNF foo=[^A-Z] EBNF] call
] unit-test
[
{ V{ 49 } } [
#! Test direct left recursion. Currently left recursion should cause a
#! failure of that parser.
"1+1" [EBNF num=([0-9])+ expr=expr "+" num | num EBNF] call
] must-fail
#! Using packrat, so first part of expr fails, causing 2nd choice to be used
"1+1" [EBNF num=([0-9])+ expr=expr "+" num | num EBNF] call parse-result-ast
] unit-test
[
{ V{ 49 } } [
#! Test indirect left recursion. Currently left recursion should cause a
#! failure of that parser.
#! Using packrat, so first part of expr fails, causing 2nd choice to be used
"1+1" [EBNF num=([0-9])+ x=expr expr=x "+" num | num EBNF] call
] must-fail
"1+1" [EBNF num=([0-9])+ x=expr expr=x "+" num | num EBNF] call parse-result-ast
] unit-test

6
extra/peg/peg.factor
View File

@ -67,10 +67,12 @@ C: <memo-entry> memo-entry
:: apply-non-memo-rule ( r p -- ast )
[let* |
m [ fail p <memo-entry> dup p r set-memo ]
ans [ r eval-rule ]
m [ ans pos get <memo-entry> ]
|
m p r set-memo ans
ans m (>>ans)
pos get m (>>pos)
ans
] ;
: apply-memo-rule ( m -- ast )