Re: [Pharo-dev] RBPattern matching dynamic array expressions

Hi, this is good that we are discussing these problems as the pattern syntax is very powerful, but it has some inconsistencies. Now I’d say that dynamic arrays should work similarly to statements and in '{ `@first . `@second . `@third }’ `@third should not match multiple “statements” as we have a dot syntax for that. Regarding your last example '`.head `.@tail' should not parse at all (at leas according to what I have seen) but it does. It is parsed into a message node with selector `.@tail and a receiver variable node `.head. It will match well if you put a dot between statements: '`.head . `.@tail’. But yes, I’d like to have a parser failure as dot is used for defining statement nodes… By the way for testing purposes you can inspect something like: RBPatternParser parseExpression: '`.head `.@tail’ and see that it is parsed into a message node. Cheers. Uko

On 10 Dec 2016, at 10:05, stepharong <stepharong@free.fr> wrote:

Hi nicolai

I always thought that I understand and I always find a situation that totally confused me. This is why I asked some guys expert in transformation to have a look and they got confused. This is why camille teruel started to work with Mark on Phorms. But the effort got stalled.

Stef

Background :

initial question: http://forum.world.st/RewriteTool-matching-parts-of-an-array-tp4910482.html <http://forum.world.st/RewriteTool-matching-parts-of-an-array-tp4910482.html>

my fix : 18910 <https://pharo.fogbugz.com/f/cases/18910/MNU-OrderedCollection-parent-when-tr...> MNU: OrderedCollection>>parent: when trying to rewrite a tree with RBParseTreeRewriter

the error my fix introduced :-) : 19445 <https://pharo.fogbugz.com/f/cases/19445/Pattern-code-ArrayNode-matching-fail...> Pattern code ArrayNode matching failure

Question : how should a pattern with three variables (first/second/third) look like to match the expression { (1@2) . Color red . 3} and assign the (sub)-expressions 1@2 Color red 3 to the three variables first/second/third ?

Looking at the initial question "RegisterRewriteTool matching parts of an array", I was suprised that for the pattern and the dynamic array expression: pattern := '{ `@first . `@second . `@third }' expression := '{ (1@2) . Color red . 3}' the third variable matches all three expressions and the first two are empty:

RBPatternVariableNode(`@first)->an OrderedCollection() RBPatternVariableNode(`@second)->an OrderedCollection() RBPatternVariableNode(`@third)->an OrderedCollection(RBMessageNode((1 @ 2)) RBMessageNode(Color red) RBLiteralValueNode(3))

I fixed this in a way, that all three variables gets assigned one (sub)expression of the array. But the fix was wrong, now a statement-list-pattern-variable cannot be used anymore to match the array statements:

pattern := '{ `@.stmts }'. expression:= RBParser parseExpression:'{ (1@2) . Color red . 3}'.

results in an error during matching but I would expect the result: RBPatternVariableNode(`@.stmts)->an OrderedCollection(RBMessageNode((1 @ 2)) RBMessageNode(Color red) RBLiteralValueNode(3))

Now I am not sure that the pattern { `@first . `@second . `@third }' is actually a valid pattern for matching the array (sub)-expressions, the array contents is a list of three single statemts and @first isn't a statement pattern, but a pattern for an expression list.

On the other hand, if I try to match *three statements* without the being in a dynamic array: (Note the missing curly braces)

pattern := '`@first . `@second . `@third '. expression : parseExpression: ' (1@2) . Color red . 3'.

The result works as I wanted them for the array pattern:

RBPatternVariableNode(`@first)->RBMessageNode(1 @ 2) RBPatternVariableNode(`@second)->RBMessageNode(Color red) RBPatternVariableNode(`@third)->RBLiteralValueNode(3)

So, is the pattern actually right or is the matching wrong? What should I expect by these patterns and expressions:

pattern := '`@first . `@second . `@third '. expression : parseExpression: ' (1@2) . Color red . 3'.

pattern := '`.first. `.second. `.third. '. expression := ' (1@2) . Color red . 3'.

pattern := '{`.first. `.second. `.third.}'. expression := '{ (1@2) . Color red . 3}'.

pattern := '{`@.all}'. expression := '{ (1@2) . Color red . 3}'.

pattern := '{`@.all}'. expression := '{ (1@2) . Color red . 3}'.

pattern := '`.head. `.@tail'. expression := '(1@2) . Color red . 3'.

pattern := '{`.head. `.@tail}'. expression := '{(1@2) . Color red . 3}'.

I would expect all statement-pattern without the dynamic array, assign the variables to the subexpressions, and the same way for the pattern with dynamic arrays.

Btw, I don't know why this does not match pattern := '`.head `.@tail'. expression := '(1@2) . Color red . 3'.

isn't the first variable a statement pattern ? From the rewrite-tool documentation (http://www.refactory.com/tools/refactoring-browser/rewrite-tool <http://www.refactory.com/tools/refactoring-browser/rewrite-tool>):

` recurse into the thing that is matched looking for more matches @ treat the item as a list ; used for messages where the message is treated as a list of messages in a cascade . treat the item as a statement in a sequence node # matches literals

thanks in advance

nicolai

-- Using Opera's mail client: http://www.opera.com/mail/ <http://www.opera.com/mail/>