Tcl_ExprLongObj(3) Tcl Library Procedures Tcl_ExprLongObj(3)

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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

Tcl 8.0 Tcl_ExprLongObj(3)