Tcl_ExprLongObj(), Tcl_ExprDoubleObj(), Tcl_ExprBooleanObj(), Tcl_ExprObj()

evaluate an expression 

Tcl Library Procedures

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 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 (for example, 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.

PORTABILITY

Windows 10. Windows Server 2016. Windows Server 2019. Windows 11. Windows Server 2022. Windows Server 2025.

AVAILABILITY

PTC MKS Toolkit for Professional Developers
PTC MKS Toolkit for Enterprise Developers
PTC MKS Toolkit for Enterprise Developers 64-Bit Edition

SEE ALSO

Functions:
Tcl_ExprBoolean(), Tcl_ExprDouble(), Tcl_ExprLong(), Tcl_ExprString(), Tcl_GetObjResult()

PTC MKS Toolkit 10.5 Documentation Build 40.