Search found 124 matches

by HughDarwen
Tue Apr 28, 2009 11:32 am
Forum: Report a Bug
Topic: Dbrowser error displaying negative integer
Replies: 1
Views: 4164

Dbrowser error displaying negative integer

The statement "output -2;" works fine but typing just -2 in the input pane results in an error message. (I discovered this bug while testing the COMPARE_TO operator provided in OperatorsChar.d. COMPARE_TO('Date','Darwen') results in 2 but comparing those two strings the other way around fa...
by HughDarwen
Mon Mar 23, 2009 2:27 pm
Forum: Report a Bug
Topic: MAX of empty set causes internal error (sometimes)
Replies: 2
Views: 5369

MAX of empty set causes internal error (sometimes)

The current value of relvar SP is RELATION {S# CHARACTER, P# CHARACTER, Qty INTEGER} { TUPLE {S# "S1", P# "P1", Qty 300}, TUPLE {S# "S1", P# "P2", Qty 200}, TUPLE {S# "S1", P# "P3", Qty 400}, TUPLE {S# "S1", P# "P4", Qty...
by HughDarwen
Tue Oct 21, 2008 11:34 am
Forum: Rel's "DBrowser": The Rel Graphical User Interface
Topic: chosen font not activated at startup
Replies: 1
Views: 8633

chosen font not activated at startup

I change the point size to 24 for lecture-room demos, but next time I start up Dbrowser I have to do Tools/Options/Save to get the selected font to show in the lower pane (even though the menu does show the point size to have been remembered). I note that changing the font doesn't affect the enhance...
by HughDarwen
Tue Oct 21, 2008 11:30 am
Forum: Report a Bug
Topic: ctrl-tab in Dbrowser causes crash
Replies: 2
Views: 5491

ctrl-tab in Dbrowser causes crash

Just press ctrl-tab in Dbrowser, when the cursor is in the lower pane. You get a java.lang.StackOverflowError. Past releases of V3 all exhibit bad behaviour of some sort when you press Ctrl-tab. In V2 the cursor went to the location box and from there to one of the buttons.

Hugh
by HughDarwen
Mon Oct 20, 2008 10:50 am
Forum: Report a Bug
Topic: internal error on invalid attribute reference in SUMMARIZE
Replies: 2
Views: 5980

internal error on invalid attribute reference in SUMMARIZE

Many thanks for 0.3.13, which I was using when I stumbled on this one. In the expression below the second <summarize add> invalidly references an attribute defined in the first. The situation gave rise to an internal error as shown instead of a regular error message. Hugh summarize relation{tuple{a ...
by HughDarwen
Mon Oct 13, 2008 5:34 pm
Forum: Report a Bug
Topic: Strange info message after failed INSERT
Replies: 3
Views: 6890

Re: Strange info message after failed INSERT

Since I posted this one I've discovered that when an insert fails because of a mistake that gives rise to a constraint violation, and you then correct that mistake, the second insert reports twice as many tuples as it should have. It appears to have counted the ones on the failed insert as well as t...
by HughDarwen
Mon Oct 06, 2008 2:58 pm
Forum: Report a Bug
Topic: relation comparison in WHERE clause gives wrong result
Replies: 4
Views: 7708

Re: relation comparison in WHERE clause gives wrong result

I should have added that the following equivalent expression, using GROUP, works fine, as you can see: (((EXAM_MARK{ALL BUT Mark} group ( {CourseId} AS G1)) RENAME (StudentId AS S1) join (EXAM_MARK{ALL BUT Mark} group ( {CourseId} AS G2)) RENAME (StudentId AS S2)) where G1 >= G2 and S1<>S2){ALL BUT ...
by HughDarwen
Mon Oct 06, 2008 2:49 pm
Forum: Report a Bug
Topic: relation comparison in WHERE clause gives wrong result
Replies: 4
Views: 7708

relation comparison in WHERE clause gives wrong result

Using the same example as in my "join on RVA" post, also today: var EXAM_MARK base relation { StudentId CHAR, CourseId CHAR, Mark INTEGER } key {ALL BUT Mark}; EXAM_MARK := relation { tuple { StudentId 'S1', CourseId 'C1', Mark 85 }, tuple { StudentId 'S1', CourseId 'C2', Mark 49 }, tuple ...
by HughDarwen
Mon Oct 06, 2008 12:22 pm
Forum: Report a Bug
Topic: join on RVA causes run-time exception
Replies: 1
Views: 5586

join on RVA causes run-time exception

The following script gave rise to the error in question. The first two statements just create and populate a relvar. The third one is a relational expression operating on that relvar. Rel appears to get the result type right but falls over in computing the result. var EXAM_MARK base relation { Stude...
by HughDarwen
Fri Sep 26, 2008 3:05 pm
Forum: Report a Bug
Topic: Missing quote gives rise to slew of messages
Replies: 1
Views: 4740

Missing quote gives rise to slew of messages

The ERROR: line shown in my example below is correct, of course, but do we have to get all those Java messages too? It looked catastrophic, but in fact I was able to continue the Dbrowser session. (I inserted a line break in the ERROR: message because otherwise it got truncated in this copy.) Hugh '...
by HughDarwen
Fri Sep 26, 2008 2:57 pm
Forum: Report a Bug
Topic: Strange info message after failed INSERT
Replies: 3
Views: 6890

Strange info message after failed INSERT

A certain INSERT statement was correctly rejected, as follows: insert SP relation{tuple{S# 'S99', P# 'P1',Qty 120}}; ERROR: Update will cause CONSTRAINT Ca to fail. Line 1, column 48 near '120' But when I next dropped the constraint in question, something funny happened, as you can see: drop CONSTRA...
by HughDarwen
Tue Sep 23, 2008 5:01 pm
Forum: Report a Bug
Topic: Complex rel exp causes exception
Replies: 1
Views: 5335

Complex rel exp causes exception

The following expression (a solution to one of the exercises set to my 2nd-year undergrads at Warwick) gave rise to an error: WITH ( S RENAME ( S# AS SX ) ) AS RX , ( S RENAME ( S# AS SY ) ) AS RY : ( ( RX JOIN RY ) WHERE ( ( SP WHERE S# = SX ) { P# } ) = ( ( SP WHERE S# = SY ) { P# } ) ) { SX, SY }...
by HughDarwen
Tue Sep 23, 2008 4:35 pm
Forum: Discussion
Topic: Tutorial D INIT clause still not supported on base relvars
Replies: 1
Views: 8046

Tutorial D INIT clause still not supported on base relvars

Perhaps there should be a special section for discussing Rel vs Tutorial D differences. IWBNI the one mentioned in my subject line were resolved one day! I mean something like: VAR S BASE RELATION { S# CHAR, Sname CHAR, Status INTEGER, City CHAR} KEY { S# } INIT ( RELATION { TUPLE { S# 'S1', Sname '...
by HughDarwen
Wed Aug 20, 2008 3:19 pm
Forum: Report a Bug
Topic: Strange error messages
Replies: 2
Views: 6109

Re: Strange error messages

Here's another: tupple { c 'abc' } ERROR: Encountered " <STRING_LITERAL> "\'abc\' "" at line 1, column 12. Was expecting one of: "}" ... "," ... This kind of thing seems to happen whenever a key word is misspelled. The message treats some subsequent token as t...
by HughDarwen
Wed Aug 20, 2008 3:09 pm
Forum: Rel Examples
Topic: Testing strings for numeric
Replies: 4
Views: 12531

Testing strings for numeric

When we get UDT support, teachers using Chris Date's "suppliers and parts" database would like to define types such as SNO (for supplier numbers of the form "Sn", where n is a sequence of digits). With this in mind I essayed the following Tutorial D operator definition: operator ...