tcl_exprlongobj(3)

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 string or objPtr.

Tcl_Obj *objPtr (in) Pointer to an

object containing
the expression to
evaluate.

long *longPtr (out) Pointer to loca

tion in which to
store the integer
value of the
expression.

int *doublePtr (out) Pointer to loca

tion in which to
store the float
ing-point value of
the expression.

int *booleanPtr (out) Pointer to loca

tion in which to
store the 0/1
boolean value of
the expression.

Tcl_Obj **resultPtrPtr (out) Pointer to loca

tion in which to
store a pointer to
the object that is
the result of the
expression.

DESCRIPTION

These four procedures all evaluate an expression, return
ing 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 eval
uate 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 *dou_ blePtr. 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 inte ger 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 expres
sion'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

Tcl 8.0 Tcl_ExprLongObj(3)