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 an object 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 object 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 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.
SEE ALSO¶
Tcl_ExprLong, Tcl_ExprDouble, Tcl_ExprBoolean, Tcl_ExprString, Tcl_GetObjResult
KEYWORDS¶
boolean, double, evaluate, expression, integer, object, string