alashworth commented 5 years ago

Issue by tpapp Monday May 09, 2016 at 17:29 GMT Originally opened as https://github.com/stan-dev/stan/issues/1888

Introduction

Some languages now support Unicode (mostly UTF8) for writing source code. It would be great if one could also use Unicode in Stan source. (Note that comments in UTF8, or any superset that embeds ASCII, are already supported in the sense the parser just ignores them.)

Broadly, there are two possible levels of support:

in variable and function names (eg ϕ), and
in operators (eg ≤), which provide synonyms for existing ones (eg <=)
Example

This is how the 8 schools example would look like in unicode:

data {
  int<lower=0> J;             // number of schools
  real y[J];                  // estimated treatment effect (school j)
  real<lower=0> σ[J];         // std err of effect estimate (school j)
}
parameters {
  real μ;
  real θ[J];
  real<lower=0> τ;
}
model {
  θ ~ normal(μ, τ); 
  y ~ normal(θ, σ);
}

Possible benefits

more compact source code
better mapping to equations in papers
Possible downsides
editor/entry support
font support
possibly corrupted files

The first two are mitigated by the fact that ASCII is a subset of UTF8, so using the feature is optional.

UTF8 support in various languages which have interfaces for Stan

language	literals	identifiers	operators	would UTF8 variables work for interfacing with Stan?
R	yes	yes	no	yes
Python	yes	only from version 3	no	yes, even in Python 2, as they are used as literal keys
Julia	yes	yes	yes	yes
Matlab	yes	yes, but needs to be enabled	no	yes
Stata	yes	yes, from version 14	no	probably?

Editor support

Emacs

See this list for various UTF8 implementations using autocomplete, company-mode, and quail.

On May 11, 2016, at 1:24 PM, Allen Riddell notifications@github.com wrote:

Here's a link to the exact section: https://docs.python.org/2/howto/unicode.html#unicode-literals-in-python-source-code

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alashworth commented 5 years ago

Comment by ariddell Wednesday May 11, 2016 at 20:07 GMT

You're right. In Python 2.7 you can't have unicode variables. In Python 3 you can. But why does that matter? We only need unicode in the Stan program code. (Parameter lookups aren't affected since keys are and always were strings.)

alashworth commented 5 years ago

Comment by bob-carpenter Wednesday May 11, 2016 at 20:48 GMT

It looks like you use a dictionary structure for variable names.

schools_dat = { 'J': 8, 'y': [28, 8, -3, 7, -1, 1, 18, 12], 'sigma': [15, 10, 16, 11, 9, 11, 10, 18] }

Can the keys be unicode?

RStan can read data values out of the environment if they're named after variables in the Stan program. And it can attach the resulting draws as variables in the environment.

Bob

On May 11, 2016, at 4:07 PM, Allen Riddell notifications@github.com wrote:

You're right. In Python 2.7 you can't have unicode variables. In Python 3 you can. But why does that matter? We only need unicode in the Stan program code. (Parameter lookups aren't affected since keys are and always were strings.)

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alashworth commented 5 years ago

Comment by ariddell Thursday May 12, 2016 at 12:20 GMT

Python 2 has no problems with unicode dictionary keys. In fact, it can have unicode variables in the environment but you have to reference them via strings indirectly. For example, this works in Python 2:

>>> locals()[u'é'] = 9
>>> locals()[u'é']

(locals is something like baseenv or .GlobalEnv in R)

Bref, there is nothing Python 2 can't do that's relevant to supporting unicode in Stan code. The table above is inaccurate.

On 05/11, Bob Carpenter wrote:

It looks like you use a dictionary structure for variable names.

schools_dat = { 'J': 8, 'y': [28, 8, -3, 7, -1, 1, 18, 12], 'sigma': [15, 10, 16, 11, 9, 11, 10, 18] }

Can the keys be unicode?

RStan can read data values out of the environment if they're named after variables in the Stan program. And it can attach the resulting draws as variables in the environment.

Bob

On May 11, 2016, at 4:07 PM, Allen Riddell notifications@github.com wrote:

You're right. In Python 2.7 you can't have unicode variables. In Python 3 you can. But why does that matter? We only need unicode in the Stan program code. (Parameter lookups aren't affected since keys are and always were strings.)

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You are receiving this because you were mentioned. Reply to this email directly or view it on GitHub: https://github.com/stan-dev/stanc3/issues/1406

alashworth commented 5 years ago

Comment by bob-carpenter Thursday May 12, 2016 at 15:33 GMT

On May 12, 2016, at 8:20 AM, Allen Riddell notifications@github.com wrote:

Python 2 has no problems with unicode dictionary keys. In fact, it can have unicode variables in the environment but you have to reference them via strings indirectly. For example, this works in Python 2:
>>> locals()[u'é'] = 9
>>> locals()[u'é']
(locals is something like baseenv or .GlobalEnv in R)

Bref, there is nothing Python 2 can't do that's relevant to supporting unicode in Stan code. The table above is inaccurate.

You should have edit permission on the issues.

Bob

alashworth commented 5 years ago

Comment by ariddell Thursday May 12, 2016 at 16:18 GMT

I was just recording my thought on the matter. I appreciate @tpapp putting work into drafting the issue text and would prefer to leave any edits to him.

alashworth commented 5 years ago

Comment by tpapp Friday May 13, 2016 at 06:54 GMT

@ariddell: The table was accurate, but since not all Stan interfaces work the way that R/Julia does, I extended it with the information that is probably most relevant: whether the interfaces, in the way they currently operate, would support UTF8 variables for (1) passing data to Stan and (2) extracting MCMC results. Thanks for pointing this out, this is much more important than the details of UTF8 support in those languages per se.

Not being a STATA user, I am reluctant to make a definitive statement about it. If someone could help with that it would be great.

alashworth commented 5 years ago

Comment by ariddell Saturday May 14, 2016 at 23:28 GMT

One use of unicode in Stan Program code which should definitely be supported is in comments. Leaving code comments in one's native language is fairly routine in Python/Java/etc. We should at least support that in Stan.

alashworth commented 5 years ago

Comment by bob-carpenter Saturday May 14, 2016 at 23:51 GMT

Unicode in comments is OK now.

Bob

On May 14, 2016, at 7:28 PM, Allen Riddell notifications@github.com wrote:

One use of unicode in Stan Program code which should definitely be supported is in comments. Leaving code comments in one's native language is fairly routine in Python/Java/etc. We should at least support that in Stan.

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alashworth commented 5 years ago

Comment by tpapp Sunday May 15, 2016 at 07:02 GMT

Indeed UTF8 comments work fine, and I have been using them for a while. Made a clarification in the issue.

alashworth commented 5 years ago

Comment by ariddell Sunday May 15, 2016 at 14:16 GMT

UTF8 comments aren't supported in PyStan right now (non-ASCII characters will generate an error). I'll fix this. stan-dev/pystan#223

alashworth / test-issue-import

feature request: unicode in source #95

Introduction

Example

Possible benefits

Possible downsides

UTF8 support in various languages which have interfaces for Stan

Editor support

Emacs

See also