Tcl_ExprLongObj(3) Tcl Library Procedures Tcl_ExprLongObj(3)
Tcl_ExprLongObj, Tcl_ExprDoubleObj, Tcl_ExprBooleanObj, Tcl_ExprObj - evaluate an expres-
Tcl_ExprLongObj(interp, objPtr, longPtr)
Tcl_ExprDoubleObj(interp, objPtr, doublePtr)
Tcl_ExprBooleanObj(interp, objPtr, booleanPtr)
Tcl_ExprObj(interp, objPtr, resultPtrPtr)
Tcl_Interp *interp (in) Interpreter in whose context to evaluate string or
Tcl_Obj *objPtr (in) Pointer to an object containing the expression to
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 float-
ing-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 object that is the result of the expression.
These four procedures all evaluate an expression, returning the result in one of four dif-
ferent 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
object containing the expression's value at *resultPtrPtr. In this case, the caller is
responsible for calling Tcl_DecrRefCount to decrement the object's reference count when it
is finished with the object.
Tcl_ExprLong, Tcl_ExprDouble, Tcl_ExprBoolean, Tcl_ExprString, Tcl_GetObjResult
boolean, double, evaluate, expression, integer, object, string
Tcl 8.0 Tcl_ExprLongObj(3)