>>Is the following a bug in STRTRAN()? It happens in VFP 7 & 9.
>>
>>? ISNULL(STRTRAN('XXX', 'YYY', NULL)) && prints .T.
>>
>>'YYY' doesn't appear in 'XXX', so why is it substituting NULL in the first place? If the expression sought doesn't exist in the expression to be searched, I would expect to have the expression to be searched returned as is, regardless of the replacement expression.
>
>Looks like you found a bug! I also would expect this to return 'XXX' instead.

Hmm, when you work with NULLs you never know what you should expect. And in most cases you should expect NULL as a result :-)
Here a simple SQL Server T-SQL that returns the same (NULL):

declare @Test varchar(200)
SET @Test = 'YYY'
SELECT REPLACE(@test,'XXX',NULL)