Yeah, I specifically excluded ascii prime (') from special handling in jhc due to its already overloaded meaning in haskell. I just added the subscript/superscript ones to the 'trailing' character class. John On Wed, Jun 25, 2014 at 12:54 PM, Mikhail Vorozhtsov wrote:

Isn't it weird that you can't write `a₁'`? I was considering proposing

varid -> (small { small | large | digit | ' | primes } { subsup | primes }) (EXCEPT reservedid)

but felt that it would be odd to allow primes in the middle of an identifier but not super/subscripts. I wish we could just abandon things like `a'bc'd` altogether...

On 06/15/2014 03:58 AM, John Meacham wrote:

...

I have this feature in jhc, where I have a 'trailing' character class that can appear at the end of both symbols and ids.

currently it consists of

$trailing = [₀₁₂₃₄₅₆₇₈₉⁰¹²³⁴⁵⁶⁷⁸⁹₍₎⁽⁾₊₋]

John

On Sat, Jun 14, 2014 at 7:48 AM, Mikhail Vorozhtsov wrote:

...

Hello lists,

As some of you may know, GHC's support for Unicode characters in lexemes is rather crude and hence prone to inconsistencies in their handling versus the ASCII counterparts. For example, APOSTROPHE is treated differently from PRIME:

λ> data a +' b = Plus a b <interactive>:3:9: Unexpected type ‘b’ In the data declaration for ‘+’ A data declaration should have form data + a b c = ... λ> data a +′ b = Plus a b

λ> let a' = 1 λ> let a′ = 1 <interactive>:10:8: parse error on input ‘=’

Also some rather bizarre looking things are accepted:

λ> let ᵤxᵤy = 1

In the spirit of improving things little by little I would like to propose:

1. Handle single/double/triple/quadruple Unicode PRIMEs the same way as APOSTROPHE, meaning the following alterations to the lexer:

primes -> U+2032 | U+2033 | U+2034 | U+2057 symbol -> ascSymbol | uniSymbol (EXCEPT special | _ | " | ' | primes) graphic -> small | large | symbol | digit | special | " | ' | primes varid -> (small { small | large | digit | ' | primes }) (EXCEPT reservedid) conid -> large { small | large | digit | ' | primes }

2. Introduce a new lexer nonterminal "subsup" that would include the Unicode sub/superscript[1] versions of numbers, "-", "+", "=", "(", ")", Latin and Greek letters. And allow these characters to be used in names and operators:

symbol -> ascSymbol | uniSymbol (EXCEPT special | _ | " | ' | primes | subsup ) digit -> ascDigit | uniDigit (EXCEPT subsup) small -> ascSmall | uniSmall (EXCEPT subsup) | _ large -> ascLarge | uniLarge (EXCEPT subsup) graphic -> small | large | symbol | digit | special | " | ' | primes | subsup varid -> (small { small | large | digit | ' | primes | subsup }) (EXCEPT reservedid) conid -> large { small | large | digit | ' | primes | subsup } varsym -> (symbol (EXCEPT :) {symbol | subsup}) (EXCEPT reservedop | dashes) consym -> (: {symbol | subsup}) (EXCEPT reservedop)

If this proposal is received favorably, I'll write a patch for GHC based on my previous stab at the problem[2].

P.S. I'm CC-ing Cafe for extra attention, but please keep the discussion to the GHC users list.

[1] https://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts [2] https://ghc.haskell.org/trac/ghc/ticket/5108 _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

-- John Meacham - http://notanumber.net/

On 2014-06-16 at 02:26:49 +0200, Mateusz Kowalczyk wrote: [...]

While personally I like the proposal (wanted prime and sub/sup scripts way too many times), I worry what this means for compatibility reasons: suddenly we'll have code that fails to build on 7.8 and before because someone using 7.9/7.10+ used ′ somewhere.

Fwiw, we already had that situation. The following code {-# LANGUAGE UnicodeSyntax #-} module Foo where x₀ ∷ Double x₀ = 1.5 compiles with GHC ≥ 7.2, but with GHC 7.0 fails with: GHCi, version 7.0.4: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Foo ( foo.hs, interpreted ) foo.hs:5:2: lexical error at character '\8320' Failed, modules loaded: none. Cheers, hvr

Hello, Mikhail Vorozhtsov wrote:

...

I also worry (although not based on anything particular you said) whether this will not change meaning of any existing programs. Does it only allow new programs?

As far as I can see, no change in meaning. Some hacky operators and some hacky identifiers would become illegal. And some nicer ones would become legal.

I do not have an opinion for or against the proposal, but I just wanted to point out that the proposal changes the meaning of some programs, at least in theory. The following function currently evaluates to True, but with the proposed change, I think that it will evaluate to False. test = let a = () b = () a′b = False in let c′d = True in a′b Best regards, Tsuyoshi

Don't forget that for every line of haskell code on hackage there are dozens of lines used internally within organizations where compatibility beyond their target internal tools may not be a concern. Deciding on a policy of allowing primes or whatnot within an organization seems quite plausible and doesn't entail CPP concerns. John On Sun, Jun 15, 2014 at 5:26 PM, Mateusz Kowalczyk wrote:

On 06/14/2014 04:48 PM, Mikhail Vorozhtsov wrote:

...

Hello lists,

As some of you may know, GHC's support for Unicode characters in lexemes is rather crude and hence prone to inconsistencies in their handling versus the ASCII counterparts. For example, APOSTROPHE is treated differently from PRIME:

λ> data a +' b = Plus a b <interactive>:3:9: Unexpected type ‘b’ In the data declaration for ‘+’ A data declaration should have form data + a b c = ... λ> data a +′ b = Plus a b

λ> let a' = 1 λ> let a′ = 1 <interactive>:10:8: parse error on input ‘=’

Also some rather bizarre looking things are accepted:

λ> let ᵤxᵤy = 1

In the spirit of improving things little by little I would like to propose:

1. Handle single/double/triple/quadruple Unicode PRIMEs the same way as APOSTROPHE, meaning the following alterations to the lexer:

primes -> U+2032 | U+2033 | U+2034 | U+2057 symbol -> ascSymbol | uniSymbol (EXCEPT special | _ | " | ' | primes) graphic -> small | large | symbol | digit | special | " | ' | primes varid -> (small { small | large | digit | ' | primes }) (EXCEPT reservedid) conid -> large { small | large | digit | ' | primes }

2. Introduce a new lexer nonterminal "subsup" that would include the Unicode sub/superscript[1] versions of numbers, "-", "+", "=", "(", ")", Latin and Greek letters. And allow these characters to be used in names and operators:

symbol -> ascSymbol | uniSymbol (EXCEPT special | _ | " | ' | primes | subsup ) digit -> ascDigit | uniDigit (EXCEPT subsup) small -> ascSmall | uniSmall (EXCEPT subsup) | _ large -> ascLarge | uniLarge (EXCEPT subsup) graphic -> small | large | symbol | digit | special | " | ' | primes | subsup varid -> (small { small | large | digit | ' | primes | subsup }) (EXCEPT reservedid) conid -> large { small | large | digit | ' | primes | subsup } varsym -> (symbol (EXCEPT :) {symbol | subsup}) (EXCEPT reservedop | dashes) consym -> (: {symbol | subsup}) (EXCEPT reservedop)

If this proposal is received favorably, I'll write a patch for GHC based on my previous stab at the problem[2].

P.S. I'm CC-ing Cafe for extra attention, but please keep the discussion to the GHC users list.

[1] https://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts [2] https://ghc.haskell.org/trac/ghc/ticket/5108 _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

While personally I like the proposal (wanted prime and sub/sup scripts way too many times), I worry what this means for compatibility reasons: suddenly we'll have code that fails to build on 7.8 and before because someone using 7.9/7.10+ used ′ somewhere. Even using CPP based on version of the compiler used is not too great in this scenario because it doesn't bring significant practical advantage to justify the CPP clutter in code. If the choice is either extra lines due to CPP or using ‘'’ instead of ‘′’, I know which I'll go for.

I also worry (although not based on anything particular you said) whether this will not change meaning of any existing programs. Does it only allow new programs?

Will it be enabled by a pragma?

I simply worry about how practical it will be to use for actual programs and libraries that will go out on Hackage and wider world, even if it is accepted.

-- Mateusz K. _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

-- John Meacham - http://notanumber.net/