osx man page for tcl_getbooleanfromobj

Tcl_BooleanObj(3)					      Tcl Library Procedures						 Tcl_BooleanObj(3)

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

SYNOPSIS
       #include <tcl.h>

       Tcl_Obj *
       Tcl_NewBooleanObj(boolValue)

       Tcl_SetBooleanObj(objPtr, boolValue)

       int
       Tcl_GetBooleanFromObj(interp, objPtr, boolPtr)

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

       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 message 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.
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DESCRIPTION
       These procedures are used to pass boolean values to and from Tcl as Tcl_Obj's.  When storing 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 recognized 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_GetBooleanFromObj 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  inter-
       preter'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 equivalents.	The  set  of  values  for  which  Tcl_Get-
       BooleanFromObj  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_Get-
       Boolean will lead to a TCL_ERROR return.

SEE ALSO
       Tcl_NewObj, Tcl_IsShared, Tcl_GetBoolean

KEYWORDS
       boolean, object

Tcl									8.5							 Tcl_BooleanObj(3)