# New keyword 'then' as synonym for ',' **URL:** \ **Category:** Uncategorized\ **Created:** [December 24, 2021, 8:01am UTC](https://alloytools.discourse.group/t/new-keyword-then-as-synonym-for/213 "2021-12-24T08:01:11Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![esb-dev](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/esb-dev/32/63_2.png) [@esb-dev](https://alloytools.discourse.group/u/esb-dev)\ **Post date:** [December 24, 2021, 8:01am UTC](https://alloytools.discourse.group/t/new-keyword-then-as-synonym-for/213/1 "2021-12-24T08:01:11Z")
Alloy often has two notations for operators i.e. and/&&. Some people prefer the more verbose notation. I propose to introduce the operator “then” as a synonym for “,” the trace sequence operator. I think in the code one has to add just one line in Alloy.lex `"then" { return alloy_sym(yytext(), CompSym.TRCSEQ );}` after line 234. But one has to change documentation and It’s of course a question of the conceptual integrity of the language too. But imho it would fit. –Burkhardt ---
**Author:** ![peter.kriens](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/peter.kriens/32/3_2.png) [@peter.kriens](https://alloytools.discourse.group/u/peter.kriens)\ **Post date:** [December 24, 2021, 8:13am UTC](https://alloytools.discourse.group/t/new-keyword-then-as-synonym-for/213/2 "2021-12-24T08:13:35Z")
This was a bug report so @grayswandyr, @DanielJackson @aleks and others please let us know what you think. Need a resolution on this. I’ve some time over the holidays so if there is a quick resolution I can do the update. ---
**Author:** ![grayswandyr](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/grayswandyr/32/17_2.png) [@grayswandyr](https://alloytools.discourse.group/u/grayswandyr)\ **Post date:** [December 24, 2021, 9:29am UTC](https://alloytools.discourse.group/t/new-keyword-then-as-synonym-for/213/3 "2021-12-24T09:29:57Z")
Hi, I see the rationale. I don’t have a definite opinion on the matter so I’ll just list pros and cons: 1. `;` is litterally a low-precedence right-associative `and after` so we already have, by definition, a verbose notation (`and after`); 2. on the other hand, low precedence with right-associativity is really the important bit here , so with `and after` the user must stack lots of parentheses and take care that they’re balanced, plus it’s not very readable. 3. `then` may be confusing because it evokes an `if/then/else` (which, by the way, some users would be happy to have); 4. it adds yet another keyword. david ---
**Author:** ![esb-dev](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/esb-dev/32/63_2.png) [@esb-dev](https://alloytools.discourse.group/u/esb-dev)\ **Post date:** [December 24, 2021, 11:17am UTC](https://alloytools.discourse.group/t/new-keyword-then-as-synonym-for/213/4 "2021-12-24T11:17:43Z")
Hi, agree with 3. Does anyone have a better and more appropriate term? ---
**Author:** ![aleks](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/aleks/32/22_2.png) [@aleks](https://alloytools.discourse.group/u/aleks)\ **Post date:** [December 25, 2021, 6:17pm UTC](https://alloytools.discourse.group/t/new-keyword-then-as-synonym-for/213/5 "2021-12-25T18:17:11Z")
Can you provide some motivation for introducing this new keyword, i.e., something more significant than “some people prefer the more verbose notation”? For example, can you provide a snippet of Alloy that you think would look better or more readable using the `then` notation? ---
**Author:** ![esb-dev](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/esb-dev/32/63_2.png) [@esb-dev](https://alloytools.discourse.group/u/esb-dev)\ **Post date:** [December 26, 2021, 9:23am UTC](https://alloytools.discourse.group/t/new-keyword-then-as-synonym-for/213/6 "2021-12-26T09:23:44Z")
The motivation for introducing `then` came from the following example. ```auto /* Specification of a concrete scenario for the echo algorithm in Alloy using the specification in module echo_var */ // the specification of the algorithm with transition predicates initiate and so on open echo_var // the concrete example of a graph pred exampleGraph [N0, N1, N2, N3, N4, N5, N6: Node] { Node = N0 + N1 + N2 + N3 + N4 + N5 + N6 neighbors = N0->N2 + N0->N3 + N1->N2 + N1->N3 + N2->N0 + N2->N1 + N2->N3 + N2->N4 + N3->N0 + N3->N1 + N3->N2 + N3->N4 + N3->N5 + N4->N2 + N4->N3 + N4->N6 + N5->N3 + N5->N6 + N6->N4 + N6->N5 } // an explicitly given scenario run Scenario { some disj N0, N1, N2, N3, N4, N5, N6: Node { exampleGraph[N0, N1, N2, N3, N4, N5, N6] initiate[N2]; forward[N0, N2]; forward[N4, N2]; forward[N3, N4]; forward[N1, N3]; forward[N6, N4]; forward[N5, N3]; echo[N5]; echo[N6]; echo[N1]; echo[N3]; echo[N4]; echo[N0]; echo[N2]; always stutter } } for 7 Node, 15 steps ``` Someone who’s first programming language was C (as in my case) or Java (as in my students case) seeing a semicolon ` ;` thinks of a sequence of assignments and statements, _not_ of a sequence of _states_. So I thaught, that something like this would better express what we mean: ```auto initiate[N2] then forward[N0, N2] then ... then echo[N2] then always stutter ``` But I agree, it’s a minor point. Kind regards Burkhardt ---
**Author:** ![grayswandyr](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/grayswandyr/32/17_2.png) [@grayswandyr](https://alloytools.discourse.group/u/grayswandyr)\ **Post date:** [December 26, 2021, 2:00pm UTC](https://alloytools.discourse.group/t/new-keyword-then-as-synonym-for/213/7 "2021-12-26T14:00:20Z")
> [@esb-dev](#): > > Someone who’s first programming language was C (as in my case) or Java (as in my students case) seeing a semicolon ` ;` thinks of a sequence of assignments and statements, _not_ of a sequence of _states_ . Notice that it doesn’t have to be _states_. Supposing you model events (call them _ev\_i_) using the [reified-event idiom](https://alloytools.discourse.group/t/modelling-a-state-machine-in-electrum-towards-alloy-6/88), you may describe a sequence of “instructions” (that is, events): ```auto run { some ev_1; some ev_3; some ev_7 } ``` ---
**Author:** ![esb-dev](https://yyz2.discourse-cdn.com/free1/user_avatar/alloytools.discourse.group/esb-dev/32/63_2.png) [@esb-dev](https://alloytools.discourse.group/u/esb-dev)\ **Post date:** [December 27, 2021, 7:39am UTC](https://alloytools.discourse.group/t/new-keyword-then-as-synonym-for/213/8 "2021-12-27T07:39:29Z")
I should have formulated more precisely: I would like the so-called “instructions” to be understood as specifications of a _sequence of state transitions_. That’s the case in David’s example too, isn’t it?