SET DESIGN | Hackers Guide to Visual FoxPro 7.0

AllTrim(), LTrim(), RTrim(), Trim()

The functions in this group are used for removing spaces from the beginning or end of character strings. Let's clear up one thing right away: RTRIM() and TRIM() are identical. So, to paraphrase George Carlin, why are there two? Yep, it's another Xbase history thing. Way back when, the only function in this group was TRIM(), which removes trailing blanks from a string. Then LTRIM() was added to remove leading blanks. We figured the "L" stood for "Leading," but somehow people started thinking of it as "Left TRIM." Well, if there's a "Left TRIM," there must be a "Right TRIM," so RTRIM() was added to be complementary to LTRIM(). Another case of useless dBloat.

Technically, ALLTRIM(), which removes leading and trailing blanks, isn't really necessary either. You can do the same thing with LTRIM(TRIM(<a string>)). Even with a million or so iterations, the ALLTRIM() version is only slightly faster than the nested call, so it's not speed. We suppose it is a little easier to code it with ALLTRIM().

Usage

cReturnValue = ALLTRIM(cString) cReturnValue = LTRIM(cString) cReturnValue = RTRIM(cString) cReturnValue = TRIM(cString)

The trim functions are particularly useful in two places. First is when dealing with character fields that may not be full, especially if you want to measure their length. LEN(<a field>) gives you the defined length of the field, not the amount of data it actually contains. To get that, you need:

LEN(TRIM(<a field>))

or, if there may be leading blanks:

LEN(ALLTRIM(<a field>))

The second place where trimming is particularly handy is in dealing with user input. If you want to search based on an input string, it's best to trim leading and trailing blanks. Users have a tendency not to worry too much about where the cursor is when they start typing or whether they've added extra spaces at the end. Say you're looking for a particular company in TasTrade's Customer table. If the name entered by the user is in m.cCompany, it's best to:

SET ORDER TO Company_Na SEEK UPPER(ALLTRIM(m.cCompany))

Finally, notice that even ALLTRIM() doesn't remove all blanks from a string, just those at the beginning and end. Embedded blanks aren't touched—take a look at STUFF(), STRTRAN() and CHRTRAN() for that sort of thing.

Example

* If cFirstName and cLastName are fields,  * return a person's full name in the usual format * For example: Herman Munster ?ALLTRIM(cFirstName)+" "+ALLTRIM(cLastName)