FAQ
...and why the := operator is weird.

This *should* be a duplicate variable declaration error, if the it wasn't
for the := weirdness.

~
Doug.
On Saturday, June 1, 2013 12:00:38 PM UTC+8, Jesse McNelis wrote:
On Sat, Jun 1, 2013 at 1:32 PM, <ri...@mcgeer.com <javascript:>> wrote:

I'm getting the "variable declared but not used" error in the following
function, and I can't see why:

func Sqrt(x float64) float64 {
var z float64 = 1.0
for i := 0; i < 10; i++ {
z := (z*z - x)/(2.0 * z)
}
return z
}

The error is in the line "z := (z*z - x)/(2.0 * z)". But z certainly is
used; it is returned immediately following the loop. The only way this
makes sense is if the z inside the loop is different from the z outside the
loop, but that would be very odd...
Not odd at all. You declared a new variable called 'z' inside the scope of
the loop.
Go lets you have variables of the same name in different scopes and ':='
declares and assigns
to a new variable.

This is one of the reasons this compile error is important to not ignore.


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