Do we support any means of creating disjoint user-defined types, such as in SRFI-9, SRFI-99 or the R6RS record system?
WG1 voted srfi-9 before. New arguments against filter constructors were raised, so the ticket was re-opened.
References:
Rationale: SRFI-9 is flawed by the filtering constructor and a lack of extensibility in its syntax, but represents a good minimal set of features that are found everywhere.
Do we provide any binary input or output ports, and if so how do we construct them and operate on them? Can binary and textual operations be mixed on the different port types?
BinaryPortsCowan provides binary port operations, being a mild revision of the relevant parts of PortsCowan.
R6RS provides an entirely new I/O system, as well as a separate R5RS-compatible I/O system.
The withdrawn SRFI-91 provides yet another I/O system supporting binary ports.
Note this item as well as #29 and #31 specify semi-orthogonal aspects of I/O systems which are typically specified together by individual proposals. If the same proposal doesn't win for all three, the aspects will be merged as needed.
WG1 voted weakly in favor of PortsCowan before.
Rationale: I think we still need more time on this. R6RS' biggest trouble is its I/O system, and I don't want the same mistake being made again. We need more effort into this domain first by more people.
In R6RS auxiliary keywords (such as else in cond and case forms) are explicitly exported from the (rnrs base (6)) library. Do we want to bind and export these from the core library?
If else is bound in the default module, then it must be imported at the call site whenever using it in cond or it won't match hygienically.
If else is not bound in the default module, then it must not be bound or imported at the call site whenever using it in cond or it won't match hygienically.
Another option is to specify for cond and case that they match the else identifier literally, ignoring any hygiene. This breaks compatibility with R5RS and R6RS.
WG1 voted unbound previously. New issues were brought up on the list so the ticket was re-opened.
References:
Rationale: While there are advantages to being unbound, unbound is still too limited and the advantages do not outweight the disadvantages. Bound has a few disadvantages, but we gain much more flexibility and the advantages just outweigh the disadvantages. Unbound limits what you can do, while Bound presents only some minor inconvenience that sometimes occurs, but that is easily worked around in ways that aren't hacky.
We need a naming convention for the core modules and standard libraries of the new module system.
The existing break down is based on John Cowan's earlier proposal of factorings in items #71, #72, #73, #74, #75, #76, #77, as well as an I/O module breakdown in PortsCowan. There have been various tickets proposing changing this, so we are re-opening the ticket.
Rationale: I have not had enough time to look this over.
Now that we have blobs, we have to decide what to call them. R6RS uses bytevector, SRFI-4 and SRFI-68 uses u8vector, while the original WG1 proposal used blob (which is therefore the default).
Rationale: Blob doesn't give enough information to the reader and feels strange, despite its terseness. Bytevector very accurately describes the data structure we are dealing with. No matter how you decide to treat those bytes, we are still dealing with a vector of bytes, not a vector of 3 bits or something else. I disagree that there is confusion on how to use a bytevector just because the word "byte" appears in the name. On the other hand, blob gives no hints on how to use the structure at all, or even what sort of things might be available.
In R5RS syntax such as #t#f is left unspecified - some readers may parse this as the true literal followed by false. R6RS requires identifiers, characters, booleans, number objects, and . to be terminated with a "delimiter" or by the end of input.
References:
Rationale: I prefer to create less ambiguity here.
In R5RS foo#f is a valid identifier, whereas R6RS requires # to act as a delimiter, so that this would parse as the identifier foo followed by the false literal.
Rationale: We have ways such as with the vertical bar of enclosing data, so there is no reason to make something like # confusing to the reader. |foo#f| is clear, while foo#f is not, so let's make # a delimiter.
This is a change also made by R6RS (and CL).
References:
Rationale: Convincing arguments have been made as to why this is a good thing on the mailing list, and there are too many unsolved issues if we leave it as single.
References:
Rationale: R6RS makes things much easier to work with in this regard. We should adopt this. I have encountered situations where this makes a great deal of sense, especially in macro writing.
This is a change also made by R6RS, specifically:
A quasiquote expression may return either fresh, mutable objects or literal structure for any structure that is constructed at run time during the evaluation of the expression. Portions that do not need to be rebuilt are always literal BEFORE is called whenever execution enters the dynamic extent of the call to THUNK and AFTER is called whenever it exits that dynamic extent. Jeronimo Pellegrini scripsit: > According to Section 6.7.1, "Conversely, not all character ports are > binary ports -- for example, the /string ports/ discussed below". It > is not really clear to wether the document *requires* string ports not > to be binary or if it was just an example of a port that *could* be > character but not binary. I haven't thought about it, but I guess it *could* be the latter, if the environment provides a default encoding for string ports. Existing features of IEEE Scheme may be removed only if a strong case can be made that they are fundamentally flawed. Insofar as practical, the language should be backwards compatible with the IEEE standard, the R5RS standard, and an appropriate subset of the R6RS standard. Unfortunately, most programming languages give nondescript names such as DIV(IDE), QUOT(IENT), MOD(ULO), and REM(AINDER) to these operations. The language should make clear to programmers what division operations their programs are performing, especially when negative dividends and divisors can arise, but perhaps may not often arise during testing. [...] The R5RS gives the names quotient and remainder to the truncating division operator pair, and the name modulo to the remainder half of the flooring division operator pair. For all these three procedures in the R5RS, the dividend may be any integer, and the divisor may be any nonzero integer.
On the other hand, we may prefer relegating them to a backward-compatibility module.
Vote "yes" to keep, "no" to remove, and "module" to relegate to a module.
Rationale: I think we can reasonably relegate these, but I'm hesitant to remove them completely, since they tend to be very commonly used. More discussion is a good thing here.
R6RS specifies the domain of finite? and nan? as the real numbers only. I propose that finite? return #t on a non-real value iff both the real part and the imaginary part are finite and not +nan.0, and that nan? return #t on a non-real value iff either the real or the imaginary part is +nan.0.
Rationale: I don't know the ramifications of this, and I would like more discussion on this.
R5RS does not actually specify any procedures which return multiple values, and so the decision to separate multiple values to a module was reasonable. However, we also voted to make exact-integer-sqrt, which is in the base module, return multiple values, namely the root and the remainder. That would make the procedure useless unless multiple values are provided.
We can either make multiple values not a module, make exact-integer-sqrt return a list (or single integer) rather than multiple values, relegate exact-integer-sqrt to a new module, remove it altogether, or do nothing and leave the inconsistency.
Rationale: I don't want to have any procedure in the language that uses lists/pairs as intermediate container constructs, as I am offended (in some ways) by that sort of conflation of the use of lists. Values should be in the core.
Andy Wingo suggests: make the clauses in case and cond forms (without =>, naturally) be BODY instances, to allow them to have definitions. It is well defined AFAIK, and costs nothing.
The counter-argument is that it doesn't "look" like the sort of place definitions are allowed.
Rationale: There is no reason not to do this. If you don't like the style, then don't use it, but a standards body should not be in charge of dictating good style.
Rationale: These are very useful and help to discourage one-armed ifs.
These trivial syntaxes add familiarity for new Scheme programmers coming from other languages, as will almost always be the case. LOOP is too big and named-LET too alien.
Rationale: They are rarely if ever used among non-beginner Scheme programmers, and I know of very few teachers who would encourage its use. Thus, they don't provide enough usefulness to the general Scheme community to warrant standardization.
Andy Wingo suggests the R6RS handling of escaped embedded newlines:
"asdadf \ asdfadf"in R6RS has the same meaning as "asdf asdfadf". It allows you to nicely indent strings that you need to line-break for width. I suggest that the production
\ NEWLINE WHITESPACE*within string literals be elided.
Note an alternate method for handling embedded strings with nice indentation is scribble syntax.
We voted on various string syntaxes previously but did not specifically propose this R6RS extension. We should have a rationale if we don't follow it.
Rationale: This is really useful, but the scribble syntax is also very useful, and we should consider this as a separate ticket.
R5RS makes a point of specifying that supporting more than two arguments is optional. (Everything not explicitly mentioned is optional, so this may have significance.) R6RS requires accepting 2 or more arguments. Currently Racket, Gambit, Guile, Chez, Ikarus, Larceny, Ypsilon, Mosh, and Scheme 9 support the feature, whereas Gauche, MIT, Chicken, Bigloo, Scheme48/scsh, Kawa, SISC, Chibi, STklos, and SSCM don't.
Rationale: I don't understand why we would limit this. It seems like an strange limitation to enforce on users. I would like to see more rationale on why we might want to vote no, but otherwise I tihnk they should accept multiple numbers of arguments.
From the Guile manual:
These procedures accept two real numbers x and y, where the divisor y must be non-zero. centered-quotient returns the integer q and centered-remainder returns the real number r such that x = q*y + r and -|y/2| <= r < |y/2|. centered/ returns both q and r, and is more efficient than computing each separately.
Note that centered-quotient returns x/y rounded to the nearest integer. When x/y lies exactly half-way between two integers, the tie is broken according to the sign of y. If y > 0, ties are rounded toward positive infinity, otherwise they are rounded toward negative infinity. This is a consequence of the requirement that -|y/2| <= r < |y/2|.
Note that these operators are equivalent to the R6RS operators div0, mod0, and div0-and-mod0.
--Andy Wingo
Taylor Campbell thinks these are useless. We should probably have use cases for _any_ division operator we include.
Rationale: I don't understand these well enough to vote on them yet.
The documentation for `begin' specifies that it is a sequential construct; but really it splices as well, and also of course it's a keyword for the module system currently. This is inaccurate of the spec to say that "begin is for sequencing".
Suggestion: adopt the language of R6RS section 11.4.7.
--Andy Wingo
We should explain somewhere the four kinds of begins: (begin expr ...), (begin decl ...), top-level begin, and module-top-level begin. Note that R7RS like R5RS does not have (begin decl ... expr ...).
Vote yes to adopt the R6RS description, modified for differences in the language.
Rationale: I think we ought to have a splicing begin form, so I don't know what else would differ between R6RS and R7RS in this regard.
This is possibly difficult to enforce, and can break existing R5RS programs written in very bad style.
Rationale: We don't have to enforce this, but it does let people write things in a way that they can get away with being slightly lazy. Making it an error is a good thing in this case.
This is possibly difficult to enforce, and can break existing R5RS programs.
Rationale: I would like to know the ramifications of this.
Add blob, blob-map, blob-for-each, and blob conversion functions to and from lists/vectors/strings.
Ratione: I know that these would be useful, but I don't know what they would look like, and they should be in the spirit of blobs and not ad hoc.
... with extra arguments.
Rationale: This simplifies the name space and should make things easier. I like this sort of interface better than remembering another name.
R6RS provides a #vu8(...) read-syntax for bytevectors. SRFI-4 uses #u8(...).
Rationale: We should have one, regardless of what we pick, and I prefer the more descriptive (slightly) R6RS version more than the SRFI-4 version.
Add a note saying that 1@2 and (make-polar 1 2) MAY evaluate to an inexact complex number.
Rationale: I haven't thought enough about this.
The grammar in 7.1.1 allows || as an <identifier>. However, page 5 suggests the |...| form is only for convenience (e.g. |foo bar| is equivalent to foo\x20;bar). There's no way to normalise || to anything without the vertical bars that's a valid identifier. Was that intentional, or should the rule be
<vertical bar> <symbol element>+ <vertical bar>Vote remove to remove the |...| syntax altogether.
Rationale: There's no reason to limit the bar syntax when || is a perfectly good identifier. We should remove language that suggests it is only for convenience.
Should we include close-port, as a generic version of close-input-port and close-output-port?
Rationale: It's useful and general, but I'm not attached to it.
The definitions of and and or may be slightly confusing. Reword them to be more clear. One possible hiccup is that the current language permits the return of different false values, while a clearer wording may preclude this.
R6RS provides a clearer definition that does not provide wiggle room for multiple false values. Should we use that?
Rationale: We should clarify this wording specifically to eliminate this ambiguity about false values.
The language of the standard could clarify that duplicate bindings are permitted in the clauses of a let*.
Rationale: Arguably this is not necessary, but it does help people who are trying to read the standard. This is an issue that has cropped up from time to time so maybe it makes sense to include language about it in the standard, even at the expense of a bit of verbosity.
make-blob should either have an initial value argument, or rationale why it is inconsistent with make-vector and make-string.
Vote yes for an initial value argument.
Rationale: I assume that this will be an optional argument, so, yes.
There are cases when one does not want to output reader labels for shared structure, such as when you don't care (and want the output to be more legible), or when you know that the time or space requirements to construct the table will be too large.
We could offer a parameter to control this, or have a separate procedure (e.g. write/simple) which doesn't use the reader labels.
Finer grained control may also let use specify a predicate for which values are interesting (e.g. never use labels for strings), or only use labels for cycles, etc.
Rationale: Is this is common use? What would this look like? I want more discussion on this, but otherwise, I am not sure it makes sense, so I'm going with none after undecided.