Chapter 4: continued

UserTalk Operators

UserTalk generally supports the same operators as most modern programming languages, plus a few extras. To accomodate a variety of preferences, Frontier has word equivalents for many of the symbols. For example, many script writers may prefer "equals" rather than "==" which is easily confused with the "=" assignment operator.

if x equals 10
   x = 0

UserTalk also supports the extended Macintosh character set where appropriate, e.g. "≠" and "≤" are probably easier to read than "!=" and "<=".

Table 4-2. UserTalk Operators

   Operator   Purpose
-----------   ------------------------------------------------------
          =   Assignment

          +   Add numeric values
              or concatenate (join) string and character values

          -   Subtract numeric values
              or remove the first occurance of one string from another

          *   Multiplication
          /   Division (integer or real, depending on the datatypes)
          %   Modulus (remainder of integer division)

         ==
     equals   Test for equality

         !=
          ≠
  notEquals   Test for inequality

          <   lessThan   Less-than comparison

         <=
          ≤   Less-than-or-equal comparison

          >greaterThan   Greater-than comparison

          ≥
         >=   Greater-than-or-equal comparison

 beginsWith   Compare one string to the beginning of another
   contains   Determine whether one string contains another
   endsWith   Compare one string to the end of another

         ||
         or   Logical OR

         &&        and   Logical AND

          !
        not   Logical NOT

         ++   Increment
         --   Decrement
          @   Address-of
          ^   Dereference an address
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Although they aren't operators, there are a few other characters that have a particular meaning in UserTalk.

Table 4-3. Other Special Characters

  Character   Purpose
-----------   ------------------------------------------------------
      "..."   Define a string (with straight quotes)
              The string may include curly quotes.
              To include a straight quote, precede with a backslash.

      ³...²   Define a string (with curly quote)
              The string may include straight quotes.
              To include a curly quote, precede with a backslash.
              (Type curly quotes with option-[ and option-shift-[.)

      '...'   Define a character or "string4" (with single quotes)
              To include a single quote, precede with a backslash.

      [...]   Evaluate a variable or expression.
              Also used for lists, records and the object model.

    ["..."]   Include an object database name that contains spaces
              or other reserved punctuation.

          \   Treat the next character as a literal.
              (e.g. to include a quote in a quoted string)

         \t   Tab character (in a quoted string)
         \r   Return (cr) character (in a quoted string)
         \n   Linefeed (lf) or "newline" character (in a quoted string)
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UserTalk Datatypes

UserTalk is a rich language that is capable of dealing with 28 different types of data. Many of these datatypes are useful only to advanced script writers. (All datatypes are listed in DocServer.) The primary datatypes are summarized below. Note that characters and strings support the full Macintosh character set (255 characters).

Table 4-4. Common UserTalk Datatypes

Datatype       Range of Legal Values
-----------    -----------------------------------------------------
addressType    Any Object Database cell 
               or any non-existent cell in an existing table  
booleanType    True or 1, False or 0
charType       Any character, enclosed in single quotes
dateType       Any legal system date value 
directionType  up, down, left, right, 
               flatup, flatdown, nodirection
intType        -32768 to 32767
longType       -2147483648 to 2147483647
menubarType    Any Frontier menubar object 
outlineType    Any Frontier outline object 
scriptType     Any legal UserTalk script   
stringType     One or more characters, enclosed in double quotes
string4Type    Exactly four characters, enclosed in single quotes
               Used by the MacOS in several ways
tableType      Any Frontier Object Database table
wptextType     Any Frontier word processing text object
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