合金模型的一個代數組

Question

我想用Alloy來模擬代數組的結構。

一個組只有一組元素和具有某些屬性的二元關係，所以我認爲它將非常適合合金。

這是我開始與

sig Number{} 
/* I call it Number but this is really just a name for some objects that are going to be in the group */ 

sig Group{ 
member: set Number, 
product: member->member->member, /*This is the part I'm really not sure about the Group is supposed to have a a well-defined binary relation so I thought maybe I could write it like this, sort of as a Curried function...I think it's actually a ternary relation in Alloy language since it takes two members and returns a third member */ 
}{//I want to write the other group properties as appended facts here. 

some e:member | all g:member| g->e->g in product //identity element 
all g:member | some i:member| g->i->e in product /* inverses exist I think there's a problem here because i want the e to be the same as in the previous line*/ 
all a,b,c:member| if a->b->c and c->d->e and b->c->f then a->f->e //transitivity 
all a,b:member| a->b->c in product// product is well defined 

} 

Answer 1

以下是在合金編碼羣的一種方法：

module group[E] 

pred associative[o : E->E->E]{ all x, y, z : E | (x.o[y]).o[z] = x.o[y.o[z]] } 

pred commutative[o : E->E->E]{ all x, y : E | x.o[y] = y.o[x] } 

pred is_identity[i : E, o : E->E->E]{ all x : E | (i.o[x] = x and x = x.o[i]) } 

pred is_inverse[b : E->E, i : E, o : E->E->E]{ all x : E | (b[x].o[x] = i and i = x.o[b[x]]) } 

sig Group{ 
op : E -> E->one E, inv : E one->one E, id : E 
}{ 
associative[op] and is_identity[id, op] and is_inverse[inv, id, op] } 

sig Abelian extends Group{}{ commutative[op] } 

unique_identity: check { 
all g : Group, id' : E | (is_identity[id', g.op] implies id' = g.id) 
} for 13 but exactly 1 Group 

unique_inverse: check { 
all g : Group, inv' : E->E | (is_inverse[inv', g.id, g.op] implies inv' = g.inv) 
} for 13 but exactly 1 Group 

Answer 2

我剛剛瞭解了一些鋁合金的自己，但你的「逆存在」的問題看起來從謂詞邏輯角度簡單;與

some e:member { 
    all g:member | g->e->g in product //identity element 
    all g:member | some i:member | g->i->e in product // inverses exist 
} 

取代你的前兩個屬性通過將逆財產的e量詞的範圍，它指的是相同的e。

我還沒有測試過這個。