delete/2

solution.pl

@@ -43,10 +43,10 @@ If the given table does not exist, the predicate should fail.
 row(Table, Row) :-
     tabl(Table, Cols) ->
     (
-			length(Cols, L),
-			length(Row, L),
+		length(Cols, L),
+		length(Row, L),
     	apply(Table, Row) 
-    ); fail.
+    ); throw("Table doesn't exist").
 
 :- dynamic rows/1.
 /*
@@ -130,9 +130,39 @@ prompt, but which may include selectors. Selectors are terms of the form
 */
 delete(Table, Conds) :- 
 	(tabl(Table, _) ->
-		(rows(tables, Row), \+ (member(Cond, Conds), \+ Cond) -> retract(Row); true);
+		row(Table, Row),
+		does_match(Conds, Table, Row)
+	;
 		throw("Table doesn't exist")
-	).
+	); true.
+
+
+does_match([], Table, Row) :-
+	Term =.. [Table | Row],
+	retract(Term),
+	fail.
+
+does_match([Cond|Rest], Table, Row) :-
+	% Extract the operator, field and value from the condition
+	Cond =.. [Operator | T],
+	[+F, S] = T,
+
+	% Get the columns of the table
+	tabl(Table, Cols),
+
+	% Get the index of the field in the columns
+	member(F, Cols),
+	nth0(Index, Cols, F),
+
+	% Get the value of the field in the row
+	nth0(Index, Row, Value),
+
+	% Apply the operator to the value and the selector
+	apply(Operator, [Value, S]),
+
+	% Check the next condition
+	does_match(Rest, Table, Row).
+
 
 :- dynamic selec/4.
 /*

tests.pl

@@ -52,16 +52,16 @@ test(drop_inexistant, throws(_)) :-
     drop(foobar).
 
 % Test if row/2 returns the different rows of a given table.
-test(rows, cleanup(cdrop(foo))) :-
+test(row, cleanup(cdrop(foo))) :-
     create_table(foo, [bar, baz]),
     insert(foo, [1, 2]),
     insert(foo, [3, 4]),
-    rows(foo, Rows),
+    row(foo, Rows),
     assertion(length(Rows,2)).
 
 % Test if row/2 fails on an unknown table name.
 test(row_inexistant, throws(_)) :-
-    rows(foo, _Row).
+    row(foo, _Row).
 
 % Test if rows/1 works when called for a given table name.
 test(rows, cleanup(cdrop(foo))) :-