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.
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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