On Tue, 2008-11-18 at 11:51 +0000, Ross Paterson wrote:

On Tue, Nov 18, 2008 at 10:30:01AM +0000, Malcolm Wallace wrote:

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When the -XUnicodeSyntax option is specified, GHC accepts some Unicode characters including left/right arrows. Unfortunately, the letter "greek lambda" cannot be used. Are there any technical reasons to not accept it?

The "greek lambda" is a normal lower-case alphabetic character - it can be used in identifier names.

But it could be a reserved word synonymous with \. After all, \ can occur in operator symbols, but the operator \ is reserved.

Presumably that would let you do (\ x -> ...) but not (\x -> ) since the "\x" would run together and lexically it would be one identifier. Duncan

On 2008 Nov 18, at 20:53, Kazu Yamamoto (山本和彦) wrote:

If we reserve the greek lambda as special like '\', the lexer can separate <lambda>x into two tokens: <lambda> and 'x', I guess.

Not without redefining it as a symbol instead of a lowercase letter, which won't be done as previously discussed. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH

Duncan Coutts wrote:

On Tue, 2008-11-18 at 11:51 +0000, Ross Paterson wrote:

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On Tue, Nov 18, 2008 at 10:30:01AM +0000, Malcolm Wallace wrote:

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When the -XUnicodeSyntax option is specified, GHC accepts some Unicode characters including left/right arrows. Unfortunately, the letter "greek lambda" cannot be used. Are there any technical reasons to not accept it? The "greek lambda" is a normal lower-case alphabetic character - it can be used in identifier names. But it could be a reserved word synonymous with \. After all, \ can occur in operator symbols, but the operator \ is reserved.

Presumably that would let you do (\ x -> ...) but not (\x -> ) since the "\x" would run together and lexically it would be one identifier.

Exactly. Here's the relevant patch: Tue Jan 16 16:11:00 GMT 2007 Simon Marlow * Remove special lambda unicode character, it didn't work anyway Since lambda is a lower-case letter, it's debatable whether we want to steal it to mean lambda in Haskell source. However if we did, then we would probably want to make it a "special" symbol, not just a reserved symbol, otherwise writing \x->... (using unicode characters of course) wouldn't work, because \x would be treated as a single identifier, you'd need a space. Cheers, Simon

On Wed, 2008-11-19 at 15:01 +0000, Tony Finch wrote:

On Wed, 19 Nov 2008, Simon Marlow wrote:

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Tue Jan 16 16:11:00 GMT 2007 Simon Marlow * Remove special lambda unicode character, it didn't work anyway Since lambda is a lower-case letter, it's debatable whether we want to steal it to mean lambda in Haskell source. However if we did, then we would probably want to make it a "special" symbol, not just a reserved symbol, otherwise writing \x->... (using unicode characters of course) wouldn't work, because \x would be treated as a single identifier, you'd need a space.

There are a number of mathematical lambdas in Unicode (distinct from teh Greek lambdas), but they are not in the basic multilingual plane and they are presumably not very easy to type :-)

Do you know what they are? I couldn't find any other than the greek lambda λ and the latin lambda with stroke ƛ. Duncan

Some others are (I have no idea why they are referenced as "lamda" instead of "lambda"): 039B GREEK CAPITAL LETTER LAMDA 03BB GREEK SMALL LETTER LAMDA 1D27 GREEK LETTER SMALL CAPITAL LAMDA 1038D UGARITIC LETTER LAMDA 1D6B2 MATHEMATICAL BOLD CAPITAL LAMDA # <font> 039B greek capital letter lamda 1D6CC MATHEMATICAL BOLD SMALL LAMDA # <font> 03BB greek small letter lamda 1D6EC MATHEMATICAL ITALIC CAPITAL LAMDA # <font> 039B greek capital letter lamda 1D706 MATHEMATICAL ITALIC SMALL LAMDA # <font> 03BB greek small letter lamda 1D726 MATHEMATICAL BOLD ITALIC CAPITAL LAMDA # <font> 039B greek capital letter lamda 1D740 MATHEMATICAL BOLD ITALIC SMALL LAMDA # <font> 03BB greek small letter lamda 1D760 MATHEMATICAL SANS-SERIF BOLD CAPITAL LAMDA # <font> 039B greek capital letter lamda 1D77A MATHEMATICAL SANS-SERIF BOLD SMALL LAMDA # <font> 03BB greek small letter lamda 1D79A MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL LAMDA # <font> 039B greek capital letter lamda 1D7B4 MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL LAMDA # <font> 03BB greek small letter lamda jan. 2008/11/19 David Menendez :

On Wed, Nov 19, 2008 at 5:24 PM, Duncan Coutts wrote:

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On Wed, 2008-11-19 at 15:01 +0000, Tony Finch wrote:

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On Wed, 19 Nov 2008, Simon Marlow wrote:

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Tue Jan 16 16:11:00 GMT 2007 Simon Marlow * Remove special lambda unicode character, it didn't work anyway Since lambda is a lower-case letter, it's debatable whether we want to steal it to mean lambda in Haskell source. However if we did, then we would probably want to make it a "special" symbol, not just a reserved symbol, otherwise writing \x->... (using unicode characters of course) wouldn't work, because \x would be treated as a single identifier, you'd need a space.

There are a number of mathematical lambdas in Unicode (distinct from teh Greek lambdas), but they are not in the basic multilingual plane and they are presumably not very easy to type :-)

Do you know what they are? I couldn't find any other than the greek lambda λ and the latin lambda with stroke ƛ.

They're listed under Mathematical Alphanumeric Symbols. http://www.unicode.org/charts/PDF/U1D400.pdf

e.g., 1D6CC mathematical bold small lambda

-- Dave Menendez http://www.eyrie.org/~zednenem/

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On Thu, Nov 20, 2008 at 12:23, Duncan Coutts wrote:

On Thu, 2008-11-20 at 09:50 +0000, Jan Jakubuv wrote:

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Some others are (I have no idea why they are referenced as "lamda" instead of "lambda"):

Yeah, that's why I missed them. I was searching for what I thought was the correct spelling.

Same here. Another problem is font support.. none of the fonts on my system (and I have quite a lot) have these codepoints defined. One would have to open them in a font editor and copy the greek lambda. cheers, Arnar

Hi, On Thu, Nov 20, 2008 at 18:56, Colin Adams wrote:

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Another problem is font support.. none of the fonts on my system (and I have quite a lot) have these codepoints defined.

David> That seems surprising. Some of the more exotic math characters added at Unicode 3.2,4,5 are only just now getting into fonts (such as STIX and Cambria math) but (almost) any truetype or type1 font built in the last 10 years or so should have the basic latin-greek-cyrillic font set, at least.

To clarify - most of modern fonts do in deed have latin-greek-cyrillic (including the U+03BB lambda), but I was referring to the specific math symbols such as the U+1D6CC bold lam(b)da, which reside in the Supplementary Multilingual Plane (SMP). Those are indeed not present in my fonts, including Lucida Math and Adobe Mathematical Pi). cheers, Arnar

On 2008 Nov 22, at 12:12, Colin Paul Adams wrote:

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"Arnar" == Arnar Birgisson writes:

Arnar> To clarify - most of modern fonts do in deed have Arnar> latin-greek-cyrillic (including the U+03BB lambda), but I Arnar> was referring to the specific math symbols such as the Arnar> U+1D6CC bold lam(b)da, which reside in the Supplementary Arnar> Multilingual Plane (SMP). Those are indeed not present in Arnar> my fonts, including Lucida Math and Adobe Mathematical Pi).

David> On windows there's cambria math (unfortunately with a restrictive licence that restricts it to that platform, though you can get it for free by getting (for example) the free powerpoint viewer from microsoft)

for a free font with a full range of characters best bet is stix font which has been 10 years in the making and is currently between beta and

http://dejavu.sourceforge.net/ works for me. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH