Issue 19177: xcollect is ambiguously flattened (qvt-rtf)
Source: Model Driven Solutions (Dr. Edward Willink, ed(at)willink.me.uk)
Nature: Clarification
Severity: Minor
Summary: xcolect is specified to like collect, which flattens, however the xcollect pseudocode does not flatten.
Resolution: xcollect is ambiguously flattened

xcollect is specified to like collect, which flattens, however the xcollect pseudocode does not flatten.

Discussion

Ditto xcollectselect, xcollectselectOne

Once an attempt is made to put the pseudo-code through Eclipse QVTo, it is quite amazing how many different errors there are.


*spurious source/iterator arguments
*missing compute open {
*increarect non-collection returns
*incorrect accommodation of ordered collections
*no flattening
*no single values
*use of mutable Sequence rather than List
Revised Text: In 8.2.2.7 ImperativeIterateExp Collection(T)::xcollect(source, iterator, body) replace
Collection(T)::xcollect(source, iterator, body) : Sequence(TT) =
compute (res:Sequence(TT) := Sequence{})
source->forEach (iterator:T) {
var target : TT := body;
if (target<>null) res += target;
};
Collection(T)::xselect(source, iterator, condition) : Sequence(T) =
compute (res:Sequence(T) := Sequence{})
source->forEach (iterator:T) {
var target : T := iterator;
if (target<>null and condition) res += target;
};
Collection(T)::xselectOne(source, iterator, condition) : Sequence(T) =
compute (res:Sequence(T) := Sequence{})
source->forEach (iterator:T) {
var target : T := iterator;
if (target<>null and condition) {res += target; break;}
};
Collection(T)::xcollectselect(source, iterator, target, body, condition) : Sequence(TT) =
compute (res:Sequence(TT) := Sequence{})
source->forEach (iterator:T) {
var target : TT := body;
if (target<>null and condition) res += target;
};
Collection(T)::xcollectselectOne(source, iterator, target, body, condition) : Sequence(TT) =
compute (res:Sequence(TT) := Sequence{})
source->forEach (iterator:T) {
var target : TT := body;
if (target<>null and condition) {res += target; break;}
};

T and TT are respectively the type of the source elements and the type of the target elements. When applying the
imperative iterate expression if the source collection is not ordered, it is implicitly converted into the corresponding
ordered collection (Set and Bag become respectively OrderedSet and Sequence). If the condition is not given, it should be
replaced by true in the definitions above.

by
Collection(T)::xcollect(BODY) : BagOrSequence(TT) =
	compute (res : List(TT) := List{}) {
		self->forEach(COLLECTOR) {
			BODY->flatten()->forEach(target) {
			      if (target <> null) res += target;
                        };
		};
	}->asBagOrSequence();

Collection(T)::xselect(CONDITION) : BagOrOrderedSetOrSequenceOrSet(T) =
	compute (res : List(T) := List{}) {
		self->forEach(SELECTOR) {
			if (SELECTOR<> null and CONDITION) res += SELECTOR;
		};
	}->asBagOrOrderedSetOrSequenceOrSet();

Collection(T)::xselectOne(CONDITION) : T =
	compute (res : T := null) {
		self->forEach(SELECTOR) {
			if (SELECTOR<> null and CONDITION) { res := SELECTOR; break; }
		};
	};

Collection(T)::xcollectselect(BODY, CONDITION) : BagOrSequence(TT) =
	compute (res : List(TT) := List{}) {
		self->forEach(COLLECTOR) {
			BODY->flatten()->forEach(SELECTOR) {
				if (SELECTOR <> null and CONDITION) { res += SELECTOR; }
			};
	    };
	}->asBagOrSequence();

Collection(T)::xcollectselectOne(BODY, CONDITION) : TT =
	compute (res : TT := null) {
		self->forEach(COLLECTOR) {
			BODY->flatten()->forEach(SELECTOR) {
				if (SELECTOR <> null and CONDITION) { res := SELECTOR; break; }
			};
			if (res <> null) { break; }
		};
	};

where


*BagOrOrderedSetOrSequenceOrSet denotes the Bag, OrderedSet, Sequence or Set kind of the source Collection
*BagOrSequence denotes either Bag or Sequence according to whether the source Collection is unordered or ordered
*BODY is a TT-valued Imperative OCL expression that may use the COLLECTOR variable
*CONDITION is a Boolean-valued Imperative OCL expression that may use the SELECTOR variable
Actions taken:
January 9, 2014: received issue
December 22, 2015: Resolved
March 29, 2016: closed issue
Discussion: 

End of Annotations:=====

m: webmaster@omg.org
Date: 09 Jan 2014 06:38:31 -0500
To: <issues@omg.org>
Subject: Issue/Bug Report


*******************************************************************************
Name:            Edward Willink
Employer:        
mailFrom:        ed@willink.me.uk
Terms_Agreement: I agree
Specification:   QVT
Section:         8.2.2.7
FormalNumber:    1.1
Version:         1.1
Doc_Year:        2011
Doc_Month:       January
Doc_Day:         01
Page:            109
Title:           xcollect is ambiguously flattened
Nature:          Clarification
Severity:        Minor
CODE:            3TMw8
B1:              Report Issue
Remote Name:     edwillink.plus.com
Remote User:     
HTTP User Agent: Mozilla/5.0 (Windows NT 6.0; rv:26.0) Gecko/20100101 Firefox/26.0
Time:            06:38 AM


Description:

xcolect is specified to like collect, which flattens, however the xcollect pseudocode does not flatten.