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1 point by Pauan 2894 days ago | link | parent

"[...] they are essentially a way to do dynamic binding in a language like Arc that normally uses static binding. This is in large part exactly what call-w/stdin does with stdin: it sets up a dynamic binding for that function."

That is correct. In fact, in Arc 3.1, std{in,out,err} are Racket parameters[1], and call-w/std{in,out} use Racket's parameterize. My point was merely that it is useful to provide parameters to Arc programmers so they can define their own parameters beyond just stdin/stdout/stderr.

* [1]: That's why you need to use (stdin), (stdout), and (stderr) rather than stdin, stdout, and stderr.

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"And no, while Arcueid's main goal is to produce a version of Arc compatible with at least Paul Graham's Arc3.1, I am of course not above introducing improvements and extensions, provided that they do not also break compatibility."

Glad to hear it. I would just like to note that any changes whatsoever will break compatibility. For instance, if you provide a "parameterize" form, a library written in Arc might also define a "parameterize" global, etc. My feeling on such things is that there should be a social convention for specifying implementation-specific global variables.

Something like, "if a global variable starts with % it is implementation-defined, so portable Arc libraries shouldn't use or define global variables starting with %".

Then your implementation could provide "%parameterize" to Arc and there would be no problems, because Arc libraries aren't supposed to use variables starting with %, so there's no conflict.

This should be solely a social convention, not enforced by the compiler. I may want to write an Arc library that does use/define implementation-specific globals, while understanding that such a library won't be portable and may break in the future.