strange evaluation Window function and SRF functions?

Hello<br /><br />I seen nice trick based on window function <a
href="http://stackoverflow.com/questions/11700930/how-can-i-trim-a-text-array-in-postgresql">http://stackoverflow.com/questions/11700930/how-can-i-trim-a-text-array-in-postgresql</a><br
/><br/>but isn't it example of wrong evaluation? Result of row_number is not correct<br /><br />Regards<br /><br
/>Pavel<br />