Metamath Proof Explorer


Definition df-comlaw

Description: The commutative law for binary operations, see definitions of laws A2. and M2. in section 1.1 of Hall p. 1, or definition 8 in BourbakiAlg1 p. 7: the value of a binary operation applied to two operands equals the value of a binary operation applied to the two operands in reversed order. By this definition, the commutative law is expressed as binary relation: a binary operation is related to a set by comLaw if the commutative law holds for this binary operation regarding this set. Note that the binary operation needs neither to be closed nor to be a function. (Contributed by AV, 7-Jan-2020)

Ref Expression
Assertion df-comlaw comLaw=om|xmymxoy=yox

Detailed syntax breakdown

Step Hyp Ref Expression
0 ccomlaw classcomLaw
1 vo setvaro
2 vm setvarm
3 vx setvarx
4 2 cv setvarm
5 vy setvary
6 3 cv setvarx
7 1 cv setvaro
8 5 cv setvary
9 6 8 7 co classxoy
10 8 6 7 co classyox
11 9 10 wceq wffxoy=yox
12 11 5 4 wral wffymxoy=yox
13 12 3 4 wral wffxmymxoy=yox
14 13 1 2 copab classom|xmymxoy=yox
15 0 14 wceq wffcomLaw=om|xmymxoy=yox