Operations with character values Foundation

Character strings are a series of ASCII characters enclosed in a set delimiting characters (see table). The operators that work with values of "character" data type include the concatenation, comparison and assignment operators. Concatenation means "addition of characters" and describes combining two character values in order to form a new character string. The following table lists all of the operators which can be used with values of "character" data type:

Four operators can be used for concatenating character values. Of these, two are inline operators:

cOne := "One   " 
cTwo := "Two  " 
? "|"+ cOne + cTwo + "|"         // result: |One   Two  | 
? "|"+ cOne - cTwo + "|"         // result: |OneTwo     | 

? "|"+ cOne += cTwo + "|"        // result: |One   Two  | 
? "|"+ cOne -= cTwo + "|"        // result: |One   TwoTwo     | 

Concatenating characters using the minus operator causes blank spaces at the end of the left operand to be removed and attached to the end of the resulting character string.

The operator == performs a binary comparison between two character strings and determines whether two character values cLeft and cRight are identical:

cLeft  := "Xbase++" 
cRight := "Xbase++   " 

? cLeft == cRight                // result: .F. 
? cLeft == RTrim(cRight)         // result: .T. 

The settings SET EXACT and SET LEXICAL are considered by all other comparison operators when comparing characters or character strings. When SET LEXICAL is set to OFF (default setting), characters are compared with each other based on the collation table specified via the SET COLLATION command.

With SET EXACT OFF characters are compared up to the length of the right character string cRight. When SET EXACT ON is set, the string are compared up to the length of the left character string cLeft. Blank spaces (Chr(32)) at the end of the two character strings are not considered. If cRight contains a null string (""), the simple equality operator = always returns the value .T. (true) when SET EXACT OFF is set. It always returns the value .F. (false) if SET EXACT ON is set,. The other comparison operators <>, >, >=, <, <= perform similar comparisons.

cLeft  := "Xbase++" 
cRight := "Xbase++   " 

SET EXACT OFF 
? cLeft = cRight                 // result: .F. 
? cLeft = ""                     // result: .T. 

SET EXACT ON 
? cLeft = cRight                 // result: .T. 
? cLeft = ""                     // result: .F. 

SET LEXICAL ON has precedence over SET EXACT ON. With SET LEXICAL ON, character comparisons are made on the basis of the lexical character value defined by the country specific settings of the operating system. The lexical value of one or more characters can be redefined using the function SetLexrule() (see the reference documentation for SetLexrule()).

When SET LEXICAL ON is set, character strings whose lexical meanings are identical but whose actual characters are different can be compared with each other. The definition of lexical comparison rules with SetLexrule() is appropriate for language specific special characters like the German umlauts or the German "ß":

SetLexrule( "ü" , "ue" )         // ü  -> ue 
SetLexrule( "ay", "ei" )         // ay -> ei 
SetLexrule( "ß" , "ss" )         // ß  -> ss 

SET LEXICAL OFF 

? "Grüße"  = "Gruesse"           // result: .F. 
? "Müller" = "Mueller"           // result: .F. 
? "Mayer"  = "Meier"             // result: .F. 

SET LEXICAL ON 
? "Grüße"  = "Gruesse"           // result: .T. 
? "Müller" = "Mueller"           // result: .T. 
? "Mayer"  = "Meier"             // result: .T. 

The following table lists all the functions of the Xbase++ runtime library that perform operations on character values or manipulate character strings. A short overview of the use of these functions follows the table.

The functions in the table are categorized into groups below and short code examples are shown for each group. A detailed description of each of these functions is found in the Xbase++ reference documentation.

Extract characters

? Left("Xbase++", 2)             // result: Xb 
? Right("Xbase++", 2)            // result: ++ 
? SubStr("Xbase++", 2, 4)        // result: base 

Replace characters

? StrTran("Xbase++", "++", "-3") // result: Xbase-3 
? Stuff("Xbase++", 2, 4 , "tra") // result: Xtra++ 

Functions for blank spaces

? "|"+        "  Xbase++  " +"|" // result: |  Xbase++  | 
? "|"+Alltrim("  Xbase++  ")+"|" // result: |Xbase++| 
? "|"+  LTrim("  Xbase++  ")+"|" // result: |Xbase++  | 
? "|"+  RTrim("  Xbase++  ")+"|" // result: |  Xbase++| 
? "|"+   Trim("  Xbase++  ")+"|" // result: |  Xbase++| 
? "|"+  Space(11)           +"|" // result: |           | 

Search characters

? At("base","Xbase++")           // result: 2 
? Rat("e"  ,"Xbase++")           // result: 5 

Convert characters

? Asc("A")                       // result: 65 
? CtoD("12/06/94")               // result: 12/06/94 
? Lower("XBASE++")               // result: xbase++ 
? PadC("Xbase++", Chr(176), 11)  // result: °°Xbase++°° 
? PadL("Xbase++", Chr(176), 11)  // result: °°°°Xbase++ 
? PadR("Xbase++", Chr(176), 11)  // result: Xbase++°°°° 
? Transform("Xbase++", "@!")     // result: XBASE++ 
? Upper("Xbase++")               // result: XBASE++ 
? Val("123")                     // result:        123 

Test character strings

? Empty( Space(11) )             // result: .T. 
? IsAlpha("Xbase++")             // result: .T. 
? IsDigit("Xbase++")             // result: .F. 
? IsLower("Xbase++")             // result: .F. 
? IsUpper("Xbase++")             // result: .T. 
? Len("Xbase++")                 // result:          7 

Other functions for character values

? Replicate("Xb",5)              // result: XbXbXbXbXb 
? Type("1")                      // result: N 
? Valtype("1")                   // result: C