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From: hasan@eclipse.stanford.edu (Waqar Hasan)
Newsgroups: comp.lang.scheme
Subject: semantics of procedure calls
Message-ID: <1991Feb28.230440.1762@Neon.Stanford.EDU>
Date: 28 Feb 91 23:04:40 GMT
Sender: news@Neon.Stanford.EDU (USENET News System)
Organization: Hewlett-Packard Labs
Lines: 27

I am new to Scheme and my source of information is the R^3 report on Scheme.

I am considering using the primitive expressions of Scheme as part of a
database language. The language is an interface language to a data server
running on a multi-processor machine.

I would like to seek clarification on the semantics of procedure calls.
The report states that arguments to a procedure are evaluated in an
"indeterminate order".

Does this mean any particular evaluation should be equivalent to some
serial order or are there no restrictions?

Example: Consider (f (+ e1 e2) (+ e3 e4))
The order of evaluation e3, e4, e1, e2 is a serialization 
since it corresponds to evaluating the second argument and then the
first argument.
The order e1, e3, e4, e2  on the other hand is not (in general) equivalent to
to any serial evaluation of the arguments.

The phrase "indeterminate order" seems to suggest that a corresponding
serial order is required. Is that the case? Should that be the case?


-Waqar Hasan
 
 hasan@hplabs.hp.com, 415-857-4233