Tcl_ExprLongObj(3tcl) Tcl Library Procedures Tcl_ExprLongObj(3tcl)
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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 ex-
pression.
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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 com-
mand.
The interp argument refers to an interpreter used to evaluate the ex-
pression (e.g. for variables and nested Tcl commands) and to return er-
ror 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 re-
trieved using Tcl_GetObjResult. If an error occurs while executing a
Tcl command embedded in the expression then that error will be re-
turned.
If the expression is successfully evaluated, then its value is returned
in one of four forms, depending on which procedure is invoked. Tcl_Ex-
prLongObj stores an integer value at *longPtr. If the expression's ac-
tual value is a floating-point number, then it is truncated to an inte-
ger. 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 *resultP-
trPtr. In this case, the caller is responsible for calling Tcl_Decr-
RefCount 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(3tcl)
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