Tcl_ExprLong(3Tcl)					    Tcl_ExprLong(3Tcl)

NAME    [Toc]    [Back]

     Tcl_ExprLong, Tcl_ExprDouble, Tcl_ExprBoolean, Tcl_ExprString - evaluate
     an	expression

SYNOPSIS    [Toc]    [Back]

     #include <tcl.h>

     int
     Tcl_ExprLong(interp, string, longPtr)

     int
     Tcl_ExprDouble(interp, string, doublePtr)

     int
     Tcl_ExprBoolean(interp, string, booleanPtr)

     int
     Tcl_ExprString(interp, string)

ARGUMENTS    [Toc]    [Back]

     Tcl_Interp	  *interp	(in)	  Interpreter in whose context to
					  evaluate string.

     char	  *string	(in)	  Expression to	be evaluated.  Must be
					  in writable memory (the expression
					  parser makes temporary modifications
					  to the string	during parsing,	which
					  it undoes before returning).

     long	  *longPtr	(out)	  Pointer to location in which to
					  store	the integer value of the
					  expression.

     int	  *doublePtr	(out)	  Pointer to location in which to
					  store	the floating-point value of
					  the expression.

     int	  *booleanPtr	(out)	  Pointer to location in which to
					  store	the 0/1	boolean	value of the
					  expression.

DESCRIPTION    [Toc]    [Back]

     These four	procedures all evaluate	an expression, returning the result in
     one of four different forms.  The expression is given by the string
     argument, and it can have any of the forms	accepted by the	expr command.
     The interp	argument refers	to an interpreter used to evaluate the
     expression	(e.g. for variables and	nested Tcl commands) and to return
     error information.	 Interp->result	is assumed to be initialized in	the
     standard fashion when any of the procedures are invoked.





									Page 1






Tcl_ExprLong(3Tcl)					    Tcl_ExprLong(3Tcl)



     For all of	these procedures the return value is a standard	Tcl result:
     TCL_OK means the expression was successfully evaluated, and TCL_ERROR
     means that	an error occurred while	evaluating the expression.  If
     TCL_ERROR is returned then	interp->result will hold a message describing
     the error.	 If an error occurs while executing a Tcl command embedded in
     the expression then that error will be returned.

     If	the expression is successfully evaluated, then its value is returned
     in	one of four forms, depending on	which procedure	is invoked.
     Tcl_ExprLong stores an integer value at *longPtr.	If the expression's
     actual value is a floating-point number, then it is truncated to an
     integer.  If the expression's actual value	is a non-numeric string	then
     an	error is returned.

     Tcl_ExprDouble stores a floating-point value at *doublePtr.  If the
     expression's actual value is an integer, it is converted to floatingpoint.
  If	the expression's actual	value is a non-numeric string then an
     error is returned.

     Tcl_ExprBoolean stores a 0/1 integer value	at *booleanPtr.	 If the
     expression's actual value is an integer or	floating-point number, then
     Tcl_ExprBoolean stores 0 at *booleanPtr if	the value was zero and 1
     otherwise.	 If the	expression's actual value is a non-numeric string then|
     it	must be	one of the values accepted by Tcl_GetBoolean, such as ``yes'' |
     or	``no'',	or else	an error occurs.

     Tcl_ExprString returns the	value of the expression	as a string stored in
     interp->result.  If the expression's actual value is an integer then     |
     Tcl_ExprString converts it	to a string using sprintf with a ``%d''	      |
     converter.	 If the	expression's actual value is a floating-point number, |
     then Tcl_ExprString calls Tcl_PrintDouble to convert it to	a string.

KEYWORDS    [Toc]    [Back]

     boolean, double, evaluate,	expression, integer, string


									PPPPaaaaggggeeee 2222