Tcl_ExprLongObj (3)
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 *resultPtrPtr out
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 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
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