Difference between revisions of "Special Purpose Operators"

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Three special operators exist within the Recital/4GL.  These are:
 
Three special operators exist within the Recital/4GL.  These are:
 +
  
 
==The Macro Operator (&)==
 
==The Macro Operator (&)==
 
When an ’&’ ampersand character precedes a variable or an expression contained within parentheses, the result of the expression is substituted into the command.  Nested macros are not supported.
 
When an ’&’ ampersand character precedes a variable or an expression contained within parentheses, the result of the expression is substituted into the command.  Nested macros are not supported.
 +
  
 
==The Alias Operator (->)==
 
==The Alias Operator (->)==
 
An open table can be referred to by its alias name and its fields can be accessed using the alias operator.  The alias name is either a name you have specified in the USE <table> ALIAS <alias name> command, or, by default, the first ten characters of the table basename.  The letters a-z (excluding m) can also be used as an alias to the work areas 1-26 (excluding 13).  M is used to reference memory variables, so is not available as a table alias
 
An open table can be referred to by its alias name and its fields can be accessed using the alias operator.  The alias name is either a name you have specified in the USE <table> ALIAS <alias name> command, or, by default, the first ten characters of the table basename.  The letters a-z (excluding m) can also be used as an alias to the work areas 1-26 (excluding 13).  M is used to reference memory variables, so is not available as a table alias
 +
  
 
==The Dot Operator (.)==
 
==The Dot Operator (.)==

Revision as of 14:41, 24 March 2009

Three special operators exist within the Recital/4GL. These are:


The Macro Operator (&)

When an ’&’ ampersand character precedes a variable or an expression contained within parentheses, the result of the expression is substituted into the command. Nested macros are not supported.


The Alias Operator (->)

An open table can be referred to by its alias name and its fields can be accessed using the alias operator. The alias name is either a name you have specified in the USE ALIAS <alias name> command, or, by default, the first ten characters of the table basename. The letters a-z (excluding m) can also be used as an alias to the work areas 1-26 (excluding 13). M is used to reference memory variables, so is not available as a table alias

The Dot Operator (.)

The dot operator ’.’ is used to reference either the properties of objects, or it can be used interchangeably with the alias operator.


Example

// Macro Operator Example
cTABLE = [employees]
use &cTABLE
 
// Alias Operator Example
cEMPNAME = &(cTABLE + "->NAME")
 
// Dot Operator Example
use employees
 
class EmpRecord
  public:
property NAME
property SALARY
  public:
method IDENT
return "Employee Record"
endclass
 
oMYREC = new EmpRecord()
cTYPE = oMYREC.IDENT()
? cTYPE
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