Re: Multi-assign
- Posted by Fernando Nov 19, 2011
- 2204 views
Some interesting possibilities with LHS symbolic sequences:
- Initializing several variables with the same value:
{a,b,c} = 0
When the RHS is an atom, we might be able to get away with this, but once the RHS is a sequence, we strike ambiguities.
Consider ...
{a,b,c} = 1 -- Assign 1 to a, b, and c {a,b,c} = {d,e,f} -- Assign {d,e,f} to a, b, and c or -- assign d to a, e to b, and f to c?
IMHO, one of the intentions of multi-assign is to simplify the access to the elements of a returned sequence of a function. Then:
{a,b,c} = {d,e,f} -- assign d to a, e to b, and f to c
To satisfy the other case:
{a,b,c} = { {d,e,f} , {d,e,f} , {d,e,f} }
- Fernando
Yes, but the problem I see is the inconsistency that might happen.
If {a,b,c} = 1 means assign to each symbol on the LHS the value on the RHS, then why does {a,b,c} = {1,2,3} mean something different?
My first thought was: because this is the Euphoric way. Comparing:
s += 1
with:
s += {a,b,c}
In the first case, each element of s is incremented. In the second case, first element of s is added by a, second element of s is added by b, ... and NOT the first element of s is added by {a,b,c}, ... But, the assignment operator '=' does not work as the assignment WITH operator (+=, *= , etc). We cannot assign an atom to a sequence. Thus, I think you're right: there would be an inconsistency in that form of initialization similar with the inconsistency in assignment operator with assignment with operator.
It looks the same; a list of symbols on the LHS and a single value on the RHS ( a single sequence).
Or more to the point ...
{a,b,c} = func()
Would operate differently depending on whether func() returned an atom or a sequence.
Yes, the assignment would operate differently depending on the type: atom or sequence.
