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CentOS 7.0 - man page for tcl_getbooleanfromobj (centos section 3)

Tcl_BooleanObj(3)		      Tcl Library Procedures			Tcl_BooleanObj(3)


       Tcl_NewBooleanObj, Tcl_SetBooleanObj, Tcl_GetBooleanFromObj - store/retrieve boolean value
       in a Tcl_Obj

       #include <tcl.h>

       Tcl_Obj *

       Tcl_SetBooleanObj(objPtr, boolValue)

       Tcl_GetBooleanFromObj(interp, objPtr, boolPtr)

       int boolValue (in)		  Integer value to be stored as  a  boolean  value  in	a

       Tcl_Obj *objPtr (in/out) 	  Points  to the Tcl_Obj in which to store, or from which
					  to retrieve a boolean value.

       Tcl_Interp *interp (in/out)	  If a boolean value cannot be retrieved, an  error  mes-
					  sage	is left in the interpreter's result object unless
					  interp is NULL.

       int *boolPtr (out)		  Points to place where Tcl_GetBooleanFromObj stores  the
					  boolean value (0 or 1) obtained from objPtr.

       These procedures are used to pass boolean values to and from Tcl as Tcl_Obj's.  When stor-
       ing a boolean value into a Tcl_Obj, any non-zero integer value in boolValue is taken to be
       the boolean value 1, and the integer value 0 is taken to be the boolean value 0.

       Tcl_NewBooleanObj  creates  a  new  Tcl_Obj, stores the boolean value boolValue in it, and
       returns a pointer to the new Tcl_Obj.  The new Tcl_Obj has reference count of zero.

       Tcl_SetBooleanObj accepts objPtr, a pointer to an existing  Tcl_Obj,  and  stores  in  the
       Tcl_Obj	*objPtr  the  boolean  value boolValue.  This is a write operation on *objPtr, so
       objPtr must be unshared.  Attempts to write to a shared Tcl_Obj will panic.  A  successful
       write of boolValue into *objPtr implies the freeing of any former value stored in *objPtr.

       Tcl_GetBooleanFromObj  attempts	to  retrieve  a  boolean  value  from the value stored in
       *objPtr.  If objPtr holds a string value recognized by Tcl_GetBoolean, then the recognized
       boolean	value is written at the address given by boolPtr.  If objPtr holds any value rec-
       ognized as a number by Tcl, then if that value is zero a 0 is written at the address given
       by  boolPtr  and if that value is non-zero a 1 is written at the address given by boolPtr.
       In all cases where a value is written at the address given by boolPtr,  Tcl_GetBooleanFro-
       mObj  returns  TCL_OK.	If the value of objPtr does not meet any of the conditions above,
       then TCL_ERROR is returned and an error message is left in the interpreter's result unless
       interp  is  NULL.   Tcl_GetBooleanFromObj  may also make changes to the internal fields of
       *objPtr so that future calls to Tcl_GetBooleanFromObj on the same objPtr can be	performed
       more efficiently.

       Note that the routines Tcl_GetBooleanFromObj and Tcl_GetBoolean are not functional equiva-
       lents.  The set of values for which Tcl_GetBooleanFromObj will return TCL_OK  is  strictly
       larger than the set of values for which Tcl_GetBoolean will do the same.  For example, the
       value "5" passed to Tcl_GetBooleanFromObj will lead to a TCL_OK return  (and  the  boolean
       value 1), while the same value passed to Tcl_GetBoolean will lead to a TCL_ERROR return.

       Tcl_NewObj, Tcl_IsShared, Tcl_GetBoolean

       boolean, object

Tcl					       8.5				Tcl_BooleanObj(3)

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