dashes in batch file

[infogirl]

Hello, can anyone explain me what these dashes means and do in this line from batch file?

if -%1 == - GOTO error1
:error1
echo please write file name

When I write only batch file name in prompt line (Windows Vista) without any other file and run it, I get the message 'please write file name'.
I would like to know how these dashes work and where can I use it.

[Salmon Trout]

The dash is so you can test for a blank parameter. You could use any character. Often people use quotes before and after, or whatever.

if [%1==[ echo parameter is blank
if "%1"=="" echo parameter is blank
if $%1$==$$ echo paramter is blank
if cat%1==cat echo parameter is blank

[infogirl]

Thank you for timeliness. Really helped me ))