To: J3                                                     J3/18-226
From: Malcolm Cohen
Subject: Another mistake in an example
Date: 2018-June-13


1. Introduction

The "invoke" procedure in the callback example refers to "list%first%data"
but there is no "list" in sight.

This is clearly a relic of a much earlier draft where the invocations were
being done directly off the list, and therefore "list%first" should have
been "callback".

2. Edit to N2146

Page 583, C.10.3 Abstract interfaces and procedure pointer components,

In the definition of type "callback_list",
change "CLASS(callback_record),POINTER :: first => NULL()"
to     "TYPE(callback_record),POINTER :: first => NULL()"
{The procedures expect a TYPE pointer not a CLASS pointer.}

In the definition of type "callback_record",
change "CLASS(callback_record),POINTER :: next"
to     "TYPE(callback_record),POINTER :: next"
{Same reason.}

In subroutine "register_callback",
change "TYPE(callback_record),POINTER :: new,last"
to     "TYPE(callback_record),POINTER :: new"
{Because "last" is not used.}

In subroutine "invoke",
change "IF (ASSOCIATED(callback%data) THEN"
to     "IF (ASSOCIATED(callback%data)) THEN"
{Missing right parenthesis.}

and in the next line,
change "CALL callback%proc(list%first%data)"
to     "CALL callback%proc(callback%data)"
{Wrong variable.}

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