Hello
Ruby complains when it tries to parse:
"" + "".to_s +""
but the following are correct:
"" + "".to_s + ""
"" + "" +""
Is it because there is no +@ operator defined for the String class ?
If so, why the latter is parsed silently ?
Marcin Mielzynski
Is it because there is no +@ operator defined for the String class ?
no, this is this case
svg% ruby -e '"".to_s +""'
-e:1: undefined method `+@' for "":String (NoMethodError)
svg%
If so, why the latter is parsed silently ?
because with '"" + "".to_s +""' ruby has seen an identifier and it don't
expect +"" at this step
Guy Decoux
"ts" <decoux@moulon.inra.fr> schrieb im Newsbeitrag
news:200407091428.i69ESQl07744@moulon.inra.fr...
> Is it because there is no +@ operator defined for the String class ?
no, this is this case
svg% ruby -e '"".to_s +""'
-e:1: undefined method `+@' for "":String (NoMethodError)
svg%> If so, why the latter is parsed silently ?
because with '"" + "".to_s +""' ruby has seen an identifier and it
don't
expect +"" at this step
Maybe Ruby tries to parse +"" as unary plus (i.e. number sign) and then
fails on the "" part.
robert
Maybe Ruby tries to parse +"" as unary plus (i.e. number sign) and then
fails on the "" part.
run it with -w
Guy Decoux
"ts" <decoux@moulon.inra.fr> schrieb im Newsbeitrag
news:200407091512.i69FCFJ09170@moulon.inra.fr...
> Maybe Ruby tries to parse +"" as unary plus (i.e. number sign) and
then
> fails on the "" part.
run it with -w
Good point. I guess "-e:1: undefined method `+@' for "":String
(NoMethodError)" means that the unary plus is not defined for String.
Correct?
Regards
robert
Good point. I guess "-e:1: undefined method `+@' for "":String
(NoMethodError)" means that the unary plus is not defined for String.
Correct?
yes,
Guy Decoux
So
"".to_s +""
means
"".to_s(+"")
and adding parens like so:
"".to_s() +""
would correct the problem.
So
"".to_s +""
means
"".to_s(+"")
it's a little more complex 
"".to_s +""
is interpreted as
"".to_s(+"") # unary plus
and
"".to_s+""
is interpreted as
"".to_s + "" # addition
*but*
"" + "".to_s +""
is interpreted as
("" + "".to_s) +""
this is why ruby give an error, it has an unary plus which don't give a
valid expression
and adding parens like so:
"".to_s() +""
would correct the problem.
yes, because with
"" + "".to_s() +""
it's interpreted as
("" + "".to_s()) + ""
the second `+' is seen as the addition not the unary plus
like in this case
"" + "".to_s+""
Guy Decoux