NAME

       Tcl_ExprLongObj,   Tcl_ExprDoubleObj,   Tcl_ExprBooleanObj,   Tcl_ExprObj  -  evaluate  an
       expression

SYNOPSIS

       #include <tcl.h>

       int
       Tcl_ExprLongObj(interp, objPtr, longPtr)

       int
       Tcl_ExprDoubleObj(interp, objPtr, doublePtr)

       int
       Tcl_ExprBooleanObj(interp, objPtr, booleanPtr)

       int
       Tcl_ExprObj(interp, objPtr, resultPtrPtr)

ARGUMENTS

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

       Tcl_Obj *objPtr (in)                    Pointer to a value containing  the  expression  to
                                               evaluate.

       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.

       Tcl_Obj **resultPtrPtr (out)            Pointer to location in which to store a pointer to
                                               the value that is the result of the expression.
_________________________________________________________________

DESCRIPTION

       These  four  procedures  all  evaluate  an expression, returning the result in one of four
       different forms.  The expression is given by the objPtr 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.

       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 a message describing the  error
       can be retrieved using Tcl_GetObjResult.  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_ExprLongObj 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_ExprDoubleObj stores a floating-point value at *doublePtr.  If the expression's actual
       value  is an integer, it is converted to floating-point.  If the expression's actual value
       is a non-numeric string then an error is returned.

       Tcl_ExprBooleanObj stores a 0/1 integer value at *booleanPtr.  If the expression's  actual
       value  is  an  integer  or  floating-point number, then they store 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.

       If Tcl_ExprObj successfully evaluates the expression, it stores a pointer to the Tcl value
       containing  the  expression's  value  at  *resultPtrPtr.   In  this  case,  the  caller is
       responsible for calling Tcl_DecrRefCount to decrement the value's reference count when  it
       is finished with the value.

SEE ALSO

       Tcl_ExprLong, Tcl_ExprDouble, Tcl_ExprBoolean, Tcl_ExprString, Tcl_GetObjResult

KEYWORDS

       boolean, double, evaluate, expression, integer, value, string