Re: What is a type? (was Re: Fortran90 and Arrays)

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3 total messages Started by David Gudeman Sat, 11 Apr 1992 05:48

#153

Author: David Gudeman
Date: Sat, 11 Apr 1992 05:48

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In article  <BEVAN.92Apr9151907@panda.cs.man.ac.uk> Stephen J Bevan writes:
]In article <1992Apr8.180420.9294@newshost.lanl.gov> jlg@cochiti.lanl.gov (Jim Giles) writes:
]   The word `type' means any static attribute which is associated with
]   an identifier in such a way that _every_ occurrence of the identifier
]   in a given scope has that attribute.
]
]Is this is a JLG definition or do others share this view?  It
]certainly doesn't match with what my idea of a "type" is.

This is a JLG definition.  I've never heard anything remotely like it
in the literature on types.  What JLG describes is usually refered to
as a "static property of an identifier".  The word "type" has several
completely different definitions, but none that I know of refer to
static properties in general.  Furthermore, it is only in low-level
languages that type is an attribute of identifiers at all.  In
high-level languages type is an attribute of a value.

]   In this case you _may_ decide to apply the word `type' to certain
]   properties of _values_, but such a distinction is not useful. 

Humph.  Try programming in Lisp without reference to the types of
values.
-- 
					David Gudeman
gudeman@cs.arizona.edu
noao!arizona!gudeman

Re: What is a type? (was Re: Fortran90 and Arrays)

#177

Author: The Technicolour Throw-up
Date: Mon, 13 Apr 1992 12:40

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From article <15195@optima.cs.arizona.edu>, by gudeman@cs.arizona.edu (David Gudeman):
> as a "static property of an identifier".  The word "type" has several
> completely different definitions, but none that I know of refer to
> static properties in general.  Furthermore, it is only in low-level
> languages that type is an attribute of identifiers at all.  In
> high-level languages type is an attribute of a value.

Type is an attribute of value in dynamically typed languages and is an
attribute of identifiers in statically typed languages.  It has nothing to
do with the level of the language.  There are plenty of high-level languages
that use static typing (e.g. Miranda, haskell).

--
Just my two rubber ningis worth.
Name: Michael Chisnall          email: chisnall@cosc.canterbury.ac.nz
I'm not a .signature virus and nor do I play one on tv.

Re: What is a type? (was Re: Fortran90 and Arrays)

#181

Author: Jim Giles
Date: Mon, 13 Apr 1992 18:03

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In article <15195@optima.cs.arizona.edu>, gudeman@cs.arizona.edu (David Gudeman) writes:

|> [...]                 What JLG describes is usually refered to
|> as a "static property of an identifier".  The word "type" has several
|> completely different definitions, but none that I know of refer to
|> static properties in general.  Furthermore, it is only in low-level
|> languages that type is an attribute of identifiers at all.  In
|> high-level languages type is an attribute of a value.


It is absolutely false and incorrect that my definition has no application
to high-level languages.  In fact, I got this definition from the person
who wrote the abstract semantics definition for Haskell.  It was the
fact that he stated this particular insight into type (which I agreed
with) when we disagreed on so much else that particularly impressed it
into my mind.  His specific statement was, however, that the distinction
between `type' and `value' is meaningless in languages in which neither 
is static.  It was my extension of this reasoning to use this criterion 
as the definition of `type' as opposed to `value'.

J. Giles

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