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--* From: Philip Santas <santas@inf.ethz.ch>
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--* To: smwatt@watson.ibm.com, sutor@watson.ibm.com, bmt@watson.ibm.com
--* Subject: recursions in A#
--* Cc: asbugs@watson.ibm.com, jenks@watson.ibm.com, santas, bronstein, williams

--@ Fixed  by: SSD Fri Jul 16 15:21:42 1993
--@ Tested by: none
--@ Summary:   Recursive definitions are being handled as specified by the language.


We need to distinguish between two forms of definitions,

recursive and non-recursive.

Assignment to a var should be non-recursive.
Assignment to a funtion should be recursive (if needed).

Consequently one needs to distinguish also between \lambda defintions
and function definitions.
  foo(x) == b
should not be the same as
  foo == x +-> b
in general.

To be more specific:

----------------------------------------------------
#include "aslib.as"

SI ==> SingleInteger
import SI

xx:=1
xx:= xx+1   -- this should be ok

yy:SI == yy+1  -- this should report an error
               -- since yy has not been defined before the assignment.

zz:SI := zz+1  -- same error

foo() == foo() -- this should be OK
               -- functions allow recrsive defs.

goo := ():SI +-> 1   -- this should be OK.
goo := ():SI +-> goo() -- this should be OK.
                       -- notice that there is NO recursion here,
                       -- since 'goo' is NOT a function.
     -- The same if we had '=='

zoo := ():SI +-> zoo() -- this should report error.
                       -- zoo has not been defined before.

qoo == ():SI +-> qoo() -- same error as before.
----------------------------------------------------

I know that I opened a can of warms, but this is the only way
I can think of, so that to deal with the problem properly.

Philip

 
--+ #include "aslib.as"
--+ 
--+ SI ==> SingleInteger
--+ import SI
--+ 
--+ -- This is OK.
--+ xx:=1
--+ xx:= xx+1   -- this should be ok
--+ 
--+ -- The behavior of uninitialized variables is not specified at present,
--+ -- so the fact that no error is reported is not a bug.
--+ yy:SI == yy+1  -- this should report an error
--+                -- since yy has not been defined before the assignment.
--+ 
--+ -- The behavior of uninitialized variables is not specified at present,
--+ -- so the fact that no error is reported is not a bug.
--+ zz:SI := zz+1  -- same error
--+ 
--+ -- This is OK.
--+ foo():SI == foo() -- this should be OK
--+                   -- functions allow recrsive defs.
--+ 
--+ -- These are OK.
--+ goo := ():SI +-> 1   -- this should be OK.
--+ goo := ():SI +-> goo() -- this should be OK.
--+                        -- notice that there is NO recursion here,
--+                        -- since 'goo' is NOT a function.
--+      -- The same if we had '=='
--+ 
--+ -- This should not report an error, and does not.
--+ -- Lambda constructs a closure which uses the value of zoo from
--+ -- the outer lexical scope.  If its defined when you need it, you get it.
--+ zoo := ():SI +-> zoo() -- this should report error.
--+                        -- zoo has not been defined before.
--+ 
--+ -- See the note for the last example.
--+ qoo == ():SI +-> qoo() -- same error as before.