On 02/04/2015 03:52 PM, Bill Page wrote:
> The distinction between "symbol" and "identifier" is rather subtle,
> particularly in the interpreter - an identifier being something to
> which we may assign a value and a symbol being something for which
> we may substitute a value.
What I meant by "variable name" in my last mail is "identifier" here.
Identifier is probably the better name for this. It's a language
construct. Symbol is simply a type in the FriCAS type hierarchy.
Whatever can be done with something of type Symbol depends on the
library functions that have Symbol in there argument types.
The interpreter (in my eyes) is just a shell around the library and
blurs types and even the distinction between symbols and identifiers.
But all CAS I know do this.
If you restrict to library programming (i.e. just writing .spad
programs) I don't see this confusion between identifier and Symbol.
> Somewhere between Symbol and identifiers we also have something
> called Variable.
Well, Variable('x) ...
If you grep the sources, you'll find that its main use is to give 'x a
domain where only that symbol lives and nothing else. If all our
polynomials and series were without variable names (i.e. something like
SparseUnivariatePolynomial), then it would probably make sense to think
about whether Variable as a type is really needed.
Ralf
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