the '-n' conditional

[Per Fransson]

If this is the wrong group for this question can you please tell me who
to ask?

Isn't

[-n string]

and

[string]

supposed to evaluate to exactly the same thing?

When I run the following script:

#!/bin/sh
if [ -n $1 ]
then
    echo Foo
fi
# end of script

it echoes "Foo" regardless of whether there's a first parameter or not.

#!/bin/sh
if [ $1 ]
then
    echo Foo
fi
# end of script

on the other hand, only echoes "Foo" if the script is presented with a
parameter.

Why is this?

Thanx in advance.

/Per Fransson