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From: mark@cbosgd.UUCP
Newsgroups: net.micro,net.micro.apple
Subject: Re: Followup to 'In Defense of Apple Pascal'
Message-ID: <557@cbosgd.UUCP>
Date: Mon, 7-Nov-83 22:38:19 EST
Article-I.D.: cbosgd.557
Posted: Mon Nov  7 22:38:19 1983
Date-Received: Wed, 9-Nov-83 05:21:40 EST
References: <709@ihuxl.UUCP>
Organization: AT&T Bell Laboratories, Columbus
Lines: 13

The mark and release functions of Apple Pascal are straight out of
UCSD Pascal, which in turn our straight out of the P2 compiler.
They are no substitute for dispose, but are sufficient
to implement the compiler (and, indeed, are more convenient for
it than dispose).  Basically, the heap is treated as a
stack (allocated from the other end of memory).  A pointer is
kept to the top of the stack (e.g. next available place to allocate).
new grabs a hunk from the stack and increments the pointer.  Period.
No hunting from a free block.  mark saves the pointer.  release
restores the pointer from the saved value.  In effect, release frees
all memory allocated since the last mark.  This is convenient for
freeing the symbol table in a block structured language.  (I can't
remember, but I suppose the marks must stack.)