[squeak-dev] Parser question

Just wonder, if following is correct expression:


| t |
1 + t := 5

--
not works in squeak (says 'nothing more expected'), but of course


| t |
1 + (t := 5)

works as expected.


--
Best regards,
Igor Stasenko AKA sig.

>>>>> "Igor" == Igor Stasenko <[hidden email]> writes:

Igor> Just wonder, if following is correct expression:
Igor> | t |
Igor> 1 + t := 5

It seems to me that that should be wrong, because to me the assignment
operation is very low precedence. And the binary message send would therefore
be out of place. If it wasn't illegal already, I'd argue to make it illegal,
as it would lead to misleading code.


--
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
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Randal L. Schwartz wrote:
Yes, it should be wrong.  The grammar is:

   expression: keyword_expression cascaded_sends
      | variable ':=' expression

   keyword_expression: binary_expression
      | binary_expression keyword_send

   binary_expression: unary_expression
      | binary_expression binary_send

   unary_expression: primary_expression
      | unary_expression unary_send

   primary_expression: literal
      | variable
      | '(' expression ')'

   cascaded_sends: cascaded_sends ';' message_send
      | /* empty */

   message_send: keyword_send
      | binary_send
      | unary_send

   variable: IDENTIFIER
   unary_send: IDENTIFIER
   binary_send: BINOP unary_expression
   keyword_send: KEYWORD binary_expression
      | keyword_send KEYWORD binary_expression

So ':=' can only appear at toplevel or inside parentheses, and the above
is not valid.

Paolo