Question: Difficult to explain?

Some of these seem to be difficult to explain ...

 

> 

restart;

> 

Digits:=3;

3

(1)
> 

u:=1.23456;

1.23456

(2)
> 

A := [1.23456, 1.23456+0, 1.23456+x+0, 1.23456+(x+0)];
B := [u,       u+0,       u+x+0,       u+(x+0)];

[1.23456, 1.23, 1.23+x, 1.23456+x]

 

[1.23456, 1.23456, 1.23456+x, 1.23456+x]

(3)
> 

lprint(A); lprint(B);

[1.23456, 1.23, 1.23+x, 1.23456+x]

[1.23456, 1.23456, 1.23456+x, 1.23456+x]

 
> 

is(A[1]=A[2]),    is(A[3]=A[4]);

true, true

(4)
> 

evalb(A[1]=A[2]), evalb(A[3]=A[4]);

true, false

(5)
> 

is(A=B);
is~(A=~B);

false

 

[true, true, true, true]

(6)
> 

evalb(A=B);
evalb~(A=~B);

false

 

[true, true, false, true]

(7)
> 

 

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