comments

solution.pl

@@ -2,6 +2,25 @@
  * Authors:
  * Dubois Brieuc
  * Dubois Simon
+ * 
+ * Known Limitation and problems:
+ * Currently a condtion in a query as to contain no space in order to function properly
+ * Ex: the condtion +name="Dakota" will work but the conditions +name = "Dakota" 
+ * or +name="North Dakota" will not. This is due to the way we parse the query. We did it
+ * with split_string. We were not able to use the prolog_term predicate given to us.
+ * 
+ * SQL test:
+ * Test 10 failed because instead of returning [+<atom>, +<atom>] for the column name
+ * we return [<atom>, <atom>] because that's how we store the column names after an insert
+ * 
+ * Test 12 and 21:
+ * When we return row of an empty table instead of having [] we have [_] same thing happens after
+ * we drop a table.
+ * 
+ * DCG test:
+ * Test 5 failed:
+ * We don't cover the case where the number of values inserted isn't the same as the number of columns
+ * in the table.
 */
 
 :- dynamic tables/0.
@@ -159,7 +178,9 @@ delete(_, _).
 
 
 does_match([], _, _) :- !.
-
+/**
+ * fails if conditons isn't respected in row
+*/
 does_match([Cond|Rest], Table, Row) :-
 	% Extract the operator, field and value from the condition
 	Cond =.. [Operator | T],
@@ -222,13 +243,17 @@ selec(Table, _, _, _) :-
 	!.
 
 selec(Table, Selector, Cond, Projection) :-
+	%fetch columns names and all rows of Table 
 	tabl(Table, Cols),
 	row(Table, R),
+	%remove rows that don't respect the conditions
 	does_match(Cond, Table, R),
+	%reduce result to only selected columns
 	selector(R,Cols, Selector, [],[],ColumnNames,ColumnValue),
+	%reorder result to match query order
 	reverse(ColumnNames, Names),
 	reverse(ColumnValue, Values),
-	
+	%unify the lists to projection
 	Projection = Names/Values.
 
 selec(Table, *, Cond, Projection) :-
@@ -238,17 +263,18 @@ selec(Table, *, Cond, Projection) :-
 	Projection = Cols/R.
 
 /**
- * Row: A row from the table
+ * +Row: A row from the table
- * Cols: name of the column of the table
+ * +Cols: name of the column of the table
- * [Selector|Selectors] name(s) of the column(s) for selection
+ * +[Selector|Selectors] name(s) of the column(s) for selection
- * AccCols: acumulator list for the column(s) name(s)
+ * +AccCols: acumulator list for the column(s) name(s)
- * AccVals: acumulator list for the row(s) values
+ * +AccVals: acumulator list for the row(s) values
- * ColumnNames: List returning the column(s) name(s)
+ * -ColumnNames: List returning the column(s) name(s)
- * ColumnValue: List returning the row values for each column
+ * -ColumnValue: List returning the row values for each column
  * 
  * This predicate return
 */
 
+%base case
 selector(_,_,[],ColumnNames, ColumnValue, ColumnNames, ColumnValue):-!.
 
 selector(Row, Cols, [+Selector|Selectors], AccCols, AccVals, ColumnNames, ColumnValue):-
@@ -256,7 +282,7 @@ selector(Row, Cols, [+Selector|Selectors], AccCols, AccVals, ColumnNames, Column
 		%find the value corresponding to the column in the row
 		nth0(Index, Cols, Selector),
         nth0(Index, Row, Value),
-		%go to next column tho evaluate
+		%go to next column tho evaluate and store value and corresponging name
         selector(Row, Cols, Selectors, [Selector|AccCols], [Value|AccVals], ColumnNames, ColumnValue)
     ;   
 		string_concat(Selector, " isn't a column of table ", Error),
@@ -299,9 +325,7 @@ ble names are atoms, while column names should follow the format out-
 lined before (+<atom>). <cond>denotes a Prolog goal, in Prolog syntax
 — following the same format as the possible values of items of the Conds
 list passed to selec and delete.
-<value>denotes a prolog value that can be stored into a row. You do
+<value>denotes a prolog value that can be stored into a row.
-not need to handle parsing Prolog (<cond>and <value>) by yourself,
-we’ll show how to do it below.
 The semantics of this predicate is that of the SQL-predicate contained in
 the Query string.
 A “SELECT” query maps to the selec predicate, while an “INSERT”
@@ -333,24 +357,32 @@ query(Query, Result):-
 	apply(Fun, Args),
 	last(Args, Result).
 
+/**
+ * For all parse_query on Query must be initiated 
+ */
+
 /**
  * Parse SELECT * FROM <table> WHERE <conds>
 */
 parse_query(Query, selec, [AtomTable, *, AtomsConds, R]):-
+	%split the query
 	split_string(Query, " ", ",;+", SplitQuery),
 	append(["SELECT"], L1, SplitQuery),
 	append(["*"], ["FROM"|L2], L1),
 	append([Table], ["WHERE"|Conds],L2),
+	%cast into correct type
 	atom_string(AtomTable, Table),
 	maplist(parse_cond, AtomsConds, Conds),!.
 /**
  * Parse SELECT <cols> FROM <table> WHERE <conds>
 */
 parse_query(Query, selec, [AtomTable, AtomsSelectors, AtomsConds, R]):-
+	%split the query
 	split_string(Query, " ", ",;+", SplitQuery),
 	append(["SELECT"], L1, SplitQuery),
 	append(Selectors, ["FROM"|L2], L1),
 	append([Table], ["WHERE"|Conds],L2),
+	%cast into correct type
 	atom_string(AtomTable, Table),
 	maplist(atom_string, AtomsSelectors1, Selectors),
 	maplist(add_plus, AtomsSelectors, AtomsSelectors1),
@@ -360,9 +392,11 @@ parse_query(Query, selec, [AtomTable, AtomsSelectors, AtomsConds, R]):-
  * Parse SELECT * FROM <table>
 */
 parse_query(Query, selec, [AtomTable, *, R]):-
+	%split the query
 	split_string(Query, " ", ",;+", SplitQuery),
 	append(["SELECT"], L1, SplitQuery),
 	append(["*"], ["FROM",Table], L1),
+	%cast into correct type
 	atom_string(AtomTable, Table),
 	maplist(parse_cond, AtomsConds, Conds),!.
 
@@ -370,23 +404,31 @@ parse_query(Query, selec, [AtomTable, *, R]):-
  * Parse SELECT <cols> FROM <table>
 */
 parse_query(Query, selec, [AtomTable, AtomsSelectors, R]):-
+	%split the query
 	split_string(Query, " ", ",;+", SplitQuery),
 	append(["SELECT"], L1, SplitQuery),
 	append(Selectors, ["FROM",Table], L1),
+	%cast into correct type
 	atom_string(AtomTable, Table),
 	maplist(atom_string, AtomsSelectors1, Selectors),
 	maplist(add_plus, AtomsSelectors, AtomsSelectors1).
 	
 parse_query(Query, insert, [AtomTable, Values]):-
+	%split the query
 	split_string(Query, " ", '",();', SplitQuery),
 	append(["INSERT", "INTO"], L1, SplitQuery),
 	L1 = [Table | L2],
 	append(_, ["VALUES"|Values1], L2),
+	%cast into correct type
 	maplist(is_number, Values, Values1),
 	atom_string(AtomTable, Table).
 
 add_plus(+A, A).
 
+/**
+ * For all parse_cond only Cond must be initiated 
+ */
+
 % parse >= conditon
 parse_cond(+AtomLeft>=AtomRight, Cond):-
 	string_chars(Cond, Code),