Package: libparse-recdescent-perl Version: 1.94-1 Severity: minor Hi!
The tutorial mentions multiple times returning values from actions. One things it fails to mention is that calling return in an action is completly different from setting $return or just specifying the value as the last statement. See the attached example, and see the attached diff file for how removing the "return" changes the output. This is all the more difficult to debug, that the message: >>Matched subrule: [gallery]<< (return value: [1] is present even in the failing case, even though the parser retracts to the beginning, as the third column suggests. So it's somewhat misleading. This has taken me several long hours to find out (in a more complicated grammar), and I really would like to make this one thing more visible in the documentation, so that noone will have to waste his time again. regards, Marcin -- System Information: Debian Release: 3.1 APT prefers unstable APT policy: (500, 'unstable'), (1, 'experimental') Architecture: i386 (i686) Kernel: Linux 2.4.27-2-k7 Locale: LANG=pl_PL, LC_CTYPE=pl_PL (charmap=ISO-8859-2) Versions of packages libparse-recdescent-perl depends on: ii perl 5.8.4-6 Larry Wall's Practical Extraction -- no debconf information
a_test
Description: Perl program
a_test_no_return
Description: Perl program
--- a_test 2005-03-03 15:35:42.000000000 +0100
+++ a_test_no_return 2005-03-03 15:36:09.000000000 +0100
@@ -12,7 +12,7 @@
gallery: 'gallery' label '{' desc(s) '}' ';'
{
- return 1;
+ 1;
}
desc: 'desc' '"' /[^"]*/ '"' ';' { $item[3] }
Script started on czw 03 mar 2005 15:38:49 CET
]0;[EMAIL PROTECTED]: /home/porridge/[EMAIL PROTECTED]:~/tmp$ ./a_de test
Parse::RecDescent: Treating "config:" as a rule declaration
Parse::RecDescent: Treating "gallery" as a subrule match
Parse::RecDescent: Treating "EE" as a literal terminal
Parse::RecDescent: Treating "gallery:" as a rule declaration
Parse::RecDescent: Treating "gallery" as a literal terminal
Parse::RecDescent: Treating "label" as a subrule match
Parse::RecDescent: Treating "{" as a literal terminal
Parse::RecDescent: Treating "desc(s)" as a one-or-more subrule match
Parse::RecDescent: Treating "}" as a literal terminal
Parse::RecDescent: Treating ";" as a literal terminal
Parse::RecDescent: Treating "{ return 1; }" as an action
Parse::RecDescent: Treating "desc:" as a rule declaration
Parse::RecDescent: Treating "desc" as a literal terminal
Parse::RecDescent: Treating """ as a literal terminal
Parse::RecDescent: Treating "/[^"]*/" as a /../ pattern terminal
Parse::RecDescent: Treating """ as a literal terminal
Parse::RecDescent: Treating ";" as a literal terminal
Parse::RecDescent: Treating "{ $item[3] }" as an action
Parse::RecDescent: Treating "label:" as a rule declaration
Parse::RecDescent: Treating "/\w+/" as a /../ pattern terminal
printing code (22472) to RD_TRACE
1| config |Trying rule: [config] |
1| config | |"gallery exim { desc "foo";
| | |}; EE"
1| config |Trying production: [gallery 'EE'] |
1| config |Trying subrule: [gallery] |
2| gallery |Trying rule: [gallery] |
2| gallery |Trying production: ['gallery' label |
| |'{' desc '}' ';'] |
2| gallery |Trying terminal: ['gallery'] |
2| gallery |>>Matched terminal<< (return value: |
| |[gallery]) |
2| gallery | |" exim { desc "foo"; }; EE"
2| gallery |Trying subrule: [label] |
3| label |Trying rule: [label] |
3| label |Trying production: [/\w+/] |
3| label |Trying terminal: [/\w+/] |
3| label |>>Matched terminal<< (return value: |
| |[exim]) |
3| label | |" { desc "foo"; }; EE"
3| label |>>Matched production: [/\w+/]<< |
3| label |>>Matched rule<< (return value: |
| |[exim]) |
3| label |(consumed: [ exim]) |
2| gallery |>>Matched subrule: [label]<< (return |
| |value: [exim] |
2| gallery |Trying terminal: ['{'] |
2| gallery |>>Matched terminal<< (return value: |
| |[{]) |
2| gallery | |" desc "foo"; }; EE"
2| gallery |Trying repeated subrule: [desc] |
3| desc |Trying rule: [desc] |
3| desc |Trying production: ['desc' '"' /[^"]*/|
| |'"' ';'] |
3| desc |Trying terminal: ['desc'] |
3| desc |>>Matched terminal<< (return value: |
| |[desc]) |
3| desc | |" "foo"; }; EE"
3| desc |Trying terminal: ['"'] |
3| desc |>>Matched terminal<< (return value: |
| |["]) |
3| desc | |"foo"; }; EE"
3| desc |Trying terminal: [/[^"]*/] |
3| desc |>>Matched terminal<< (return value: |
| |[foo]) |
3| desc | |""; }; EE"
3| desc |Trying terminal: ['"'] |
3| desc |>>Matched terminal<< (return value: |
| |["]) |
3| desc | |"; }; EE"
3| desc |Trying terminal: [';'] |
3| desc |>>Matched terminal<< (return value: |
| |[;]) |
3| desc | |" }; EE"
3| desc |Trying action |
3| desc |>>Matched action<< (return value: |
| |[foo]) |
3| desc |>>Matched production: ['desc' '"' |
| |/[^"]*/ '"' ';']<< |
3| desc |>>Matched rule<< (return value: [foo])|
3| desc |(consumed: [ desc "foo";]) |
3| desc |Trying rule: [desc] |
3| desc |Trying production: ['desc' '"' /[^"]*/|
| |'"' ';'] |
3| desc |Trying terminal: ['desc'] |
3| desc |<<Didn't match terminal>> |
3| desc | |"}; EE"
3| desc |<<Didn't match rule>> |
2| gallery |>>Matched repeated subrule: [desc]<< |
| |(1 times) |
2| gallery | |" }; EE"
2| gallery |Trying terminal: ['}'] |
2| gallery |>>Matched terminal<< (return value: |
| |[}]) |
2| gallery | |"; EE"
2| gallery |Trying terminal: [';'] |
2| gallery |>>Matched terminal<< (return value: |
| |[;]) |
2| gallery | |" EE"
2| gallery |Trying action |
1| config |>>Matched subrule: [gallery]<< (return|
| |value: [1] |
1| config | |"gallery exim { desc "foo";
| | |}; EE"
1| config |Trying terminal: ['EE'] |
1| config |<<Didn't match terminal>> |
1| config |<<Didn't match rule>> |
parse returned undef
]0;[EMAIL PROTECTED]: /home/porridge/[EMAIL PROTECTED]:~/tmp$
Script done on czw 03 mar 2005 15:38:55 CET
Script started on czw 03 mar 2005 15:39:28 CET
]0;[EMAIL PROTECTED]: /home/porridge/[EMAIL PROTECTED]:~/tmp$
./a_test_no_return
Parse::RecDescent: Treating "config:" as a rule declaration
Parse::RecDescent: Treating "gallery" as a subrule match
Parse::RecDescent: Treating "EE" as a literal terminal
Parse::RecDescent: Treating "gallery:" as a rule declaration
Parse::RecDescent: Treating "gallery" as a literal terminal
Parse::RecDescent: Treating "label" as a subrule match
Parse::RecDescent: Treating "{" as a literal terminal
Parse::RecDescent: Treating "desc(s)" as a one-or-more subrule match
Parse::RecDescent: Treating "}" as a literal terminal
Parse::RecDescent: Treating ";" as a literal terminal
Parse::RecDescent: Treating "{ 1; }" as an action
Parse::RecDescent: Treating "desc:" as a rule declaration
Parse::RecDescent: Treating "desc" as a literal terminal
Parse::RecDescent: Treating """ as a literal terminal
Parse::RecDescent: Treating "/[^"]*/" as a /../ pattern terminal
Parse::RecDescent: Treating """ as a literal terminal
Parse::RecDescent: Treating ";" as a literal terminal
Parse::RecDescent: Treating "{ $item[3] }" as an action
Parse::RecDescent: Treating "label:" as a rule declaration
Parse::RecDescent: Treating "/\w+/" as a /../ pattern terminal
printing code (22465) to RD_TRACE
1| config |Trying rule: [config] |
1| config | |"gallery exim { desc "foo";
| | |}; EE"
1| config |Trying production: [gallery 'EE'] |
1| config |Trying subrule: [gallery] |
2| gallery |Trying rule: [gallery] |
2| gallery |Trying production: ['gallery' label |
| |'{' desc '}' ';'] |
2| gallery |Trying terminal: ['gallery'] |
2| gallery |>>Matched terminal<< (return value: |
| |[gallery]) |
2| gallery | |" exim { desc "foo"; }; EE"
2| gallery |Trying subrule: [label] |
3| label |Trying rule: [label] |
3| label |Trying production: [/\w+/] |
3| label |Trying terminal: [/\w+/] |
3| label |>>Matched terminal<< (return value: |
| |[exim]) |
3| label | |" { desc "foo"; }; EE"
3| label |>>Matched production: [/\w+/]<< |
3| label |>>Matched rule<< (return value: |
| |[exim]) |
3| label |(consumed: [ exim]) |
2| gallery |>>Matched subrule: [label]<< (return |
| |value: [exim] |
2| gallery |Trying terminal: ['{'] |
2| gallery |>>Matched terminal<< (return value: |
| |[{]) |
2| gallery | |" desc "foo"; }; EE"
2| gallery |Trying repeated subrule: [desc] |
3| desc |Trying rule: [desc] |
3| desc |Trying production: ['desc' '"' /[^"]*/|
| |'"' ';'] |
3| desc |Trying terminal: ['desc'] |
3| desc |>>Matched terminal<< (return value: |
| |[desc]) |
3| desc | |" "foo"; }; EE"
3| desc |Trying terminal: ['"'] |
3| desc |>>Matched terminal<< (return value: |
| |["]) |
3| desc | |"foo"; }; EE"
3| desc |Trying terminal: [/[^"]*/] |
3| desc |>>Matched terminal<< (return value: |
| |[foo]) |
3| desc | |""; }; EE"
3| desc |Trying terminal: ['"'] |
3| desc |>>Matched terminal<< (return value: |
| |["]) |
3| desc | |"; }; EE"
3| desc |Trying terminal: [';'] |
3| desc |>>Matched terminal<< (return value: |
| |[;]) |
3| desc | |" }; EE"
3| desc |Trying action |
3| desc |>>Matched action<< (return value: |
| |[foo]) |
3| desc |>>Matched production: ['desc' '"' |
| |/[^"]*/ '"' ';']<< |
3| desc |>>Matched rule<< (return value: [foo])|
3| desc |(consumed: [ desc "foo";]) |
3| desc |Trying rule: [desc] |
3| desc |Trying production: ['desc' '"' /[^"]*/|
| |'"' ';'] |
3| desc |Trying terminal: ['desc'] |
3| desc |<<Didn't match terminal>> |
3| desc | |"}; EE"
3| desc |<<Didn't match rule>> |
2| gallery |>>Matched repeated subrule: [desc]<< |
| |(1 times) |
2| gallery | |" }; EE"
2| gallery |Trying terminal: ['}'] |
2| gallery |>>Matched terminal<< (return value: |
| |[}]) |
2| gallery | |"; EE"
2| gallery |Trying terminal: [';'] |
2| gallery |>>Matched terminal<< (return value: |
| |[;]) |
2| gallery | |" EE"
2| gallery |Trying action |
2| gallery |>>Matched action<< (return value: [1])|
2| gallery |>>Matched production: ['gallery' label|
| |'{' desc '}' ';']<< |
2| gallery |>>Matched rule<< (return value: [1]) |
2| gallery |(consumed: [gallery exim { desc "foo";|
| |};]) |
1| config |>>Matched subrule: [gallery]<< (return|
| |value: [1] |
1| config |Trying terminal: ['EE'] |
1| config |>>Matched terminal<< (return value: |
| |[EE]) |
1| config |>>Matched production: [gallery 'EE']<<|
1| config |>>Matched rule<< (return value: [EE]) |
1| config |(consumed: []) |
?:$VAR1 = 'EE';
]0;[EMAIL PROTECTED]: /home/porridge/[EMAIL PROTECTED]:~/tmp$
Script done on czw 03 mar 2005 15:39:34 CET
--- parser1 2005-03-03 15:38:55.000000000 +0100
+++ parser2 2005-03-03 15:39:34.000000000 +0100
@@ -10,7 +10,7 @@
Parse::RecDescent: Treating "desc(s)" as a one-or-more subrule match
Parse::RecDescent: Treating "}" as a literal terminal
Parse::RecDescent: Treating ";" as a literal terminal
- Parse::RecDescent: Treating "{ return 1; }" as an action
+ Parse::RecDescent: Treating "{ 1; }" as an action
Parse::RecDescent: Treating "desc:" as a rule declaration
Parse::RecDescent: Treating "desc" as a literal terminal
Parse::RecDescent: Treating """ as a literal terminal
@@ -20,7 +20,7 @@
Parse::RecDescent: Treating "{ $item[3] }" as an action
Parse::RecDescent: Treating "label:" as a rule declaration
Parse::RecDescent: Treating "/\w+/" as a /../ pattern terminal
-printing code (22472) to RD_TRACE
+printing code (22465) to RD_TRACE
1| config |Trying rule: [config] |
1| config | |"gallery exim { desc
"foo";
| | |}; EE"
@@ -100,13 +100,20 @@
| |[;]) |
2| gallery | |" EE"
2| gallery |Trying action |
+ 2| gallery |>>Matched action<< (return value: [1])|
+ 2| gallery |>>Matched production: ['gallery' label|
+ | |'{' desc '}' ';']<< |
+ 2| gallery |>>Matched rule<< (return value: [1]) |
+ 2| gallery |(consumed: [gallery exim { desc "foo";|
+ | |};]) |
1| config |>>Matched subrule: [gallery]<< (return|
| |value: [1] |
- 1| config | |"gallery exim { desc
"foo";
- | | |}; EE"
1| config |Trying terminal: ['EE'] |
- 1| config |<<Didn't match terminal>> |
- 1| config |<<Didn't match rule>> |
-parse returned undef
+ 1| config |>>Matched terminal<< (return value: |
+ | |[EE]) |
+ 1| config |>>Matched production: [gallery 'EE']<<|
+ 1| config |>>Matched rule<< (return value: [EE]) |
+ 1| config |(consumed: []) |
+?:$VAR1 = 'EE';
]0;[EMAIL PROTECTED]: /home/porridge/[EMAIL PROTECTED]:~/tmp$
