View source for F$TYPE

'''F$TYPE''' is a [[Lexical functions|lexical function]] that  returns the data type of a symbol. The string INTEGER is returned if the symbol is equated to an integer, or if the symbol is equated to a string whose characters form a valid integer. The string STRING is returned if the symbol is equated to a character string whose characters do not form a valid integer. If the symbol is undefined, a null string ("")  is returned. 

=Syntax=

F$TYPE(symbol-name)

=Return Value=

The string INTEGER is returned if the symbol is equated to an integer, or if the symbol is equated to a string whose characters form a valid integer. 

If the symbol has been produced by a call to the [[F$CONTEXT]] function with a context type of PROCESS or by a call to the [[F$PID]] function, the string returned is PROCESS_CONTEXT. A symbol retains this type until [[F$CONTEXT]] is called with the symbol and the CANCEL keyword, or until a null string ("")  is returned by a call to F$PID. Similarly, the return value is the string CLUSTER_SYSTEM_CONTEXT for symbols created by the F$CSID function. If the symbol is a context symbol, then the return value will be one of the types shown in the following table. 

{|class="wikitable"
! colspan="col" | Symbol Type
! colspan="col" | Lexical Creating Symbol
|-
| PROCESS_CONTEXT
| F$PID or F$CONTEXT (with PROCESS context type)
|-
| CLUSTER_SYSTEM_CONTEXT
| [[F$CSID]]
|}

=Arguments=

==symbol-name==
Specifies the name of the symbol to be evaluated. 

=Examples=

 $ NUM = "52" 
 $ TYPE = F$TYPE(NUM) 
 $ SHOW SYMBOL TYPE 
   TYPE = "INTEGER" 

This example uses the F$TYPE function to determine the data type of the symbol NUM. NUM is equated to the character string "52". Because the characters in the string form a valid integer, the F$TYPE function returns the string INTEGER. 

 $ NUM = 52 
 $ TYPE = F$TYPE(NUM) 
 $ SHOW SYMBOL TYPE 
   TYPE = "INTEGER" 

In this example, the symbol NUM is equated to the integer 52. The F$TYPE function shows that the symbol has an integer data type. 

 $ CHAR = "FIVE" 
 $ TYPE = F$TYPE(CHAR) 
 $ SHOW SYMBOL TYPE 
   TYPE = "STRING" 

In this example, the symbol CHAR is equated to the character string FIVE. Because the characters in this string do not form a valid integer, the F$TYPE function shows that the symbol has a string value. 

 $ x = F$CONTEXT("PROCESS",CTX,"USERNAME","SMITH") 
 $ TYPE = F$TYPE(CTX) 
 $ SHOW SYMBOL TYPE 
   TYPE = "PROCESS_CONTEXT" 
 $ x = F$CONTEXT("PROCESS",CTX,"CANCEL") 
 $ TYPE = F$TYPE(CTX) 
 $ SHOW SYMBOL TYPE 
   TYPE = "" 

In this example, the F$TYPE function returns the string PROCESS_CONTEXT because the symbol has been produced by a call to the F$CONTEXT function with a context type of PROCESS. The symbol returns this type until F$CONTEXT is called with the symbol and the selection-item argument value CANCEL.

 $ TYPE = F$TYPE(UNDEF) 
 $ SHOW SYMBOL TYPE 
   TYPE = "" 

This example uses the F$TYPE function to determine that the symbol UNDEF is undefined. Because the symbol has not been set to a value, the F$TYPE function returns the empty string. 

[[Category:Lexical Functions]]