All right, I think I've solved the expansion problem I described before: to ensure that the first input is expanded when it is passed to Lua, I have to pass it as [==[#1]==], not "#1". But the updated MWE below still does not seem to work, as the \DoIfPrefixElse macro is printing "NOP" instead of "YES": ``` \starttexdefinition loc [#1] \doifassignmentelse{#1} { % if an assignment, then parse and format accordingly \getparameters[loc][#1] % Was a section number specified? \doifdefined{locsec} { § \locsec } } { % otherwise, just print the input as-is #1 } \stoptexdefinition \def\DoIfPrefixElse#1#2{\ctxlua{commands.doifelse(string.find([==[#2]==],"^"..[==[#1]==]))}} \def\currentbtxloctext{\loc[sec=31]} \starttext \currentbtxloctext\blank \DoIfPrefixElse{§}{\currentbtxloctext}{YES}{NOP} \stoptext ``` Indeed, if I add a simple \doifelse equality check, it looks like the value I expect is not the same as what the macro produces, even though they look identical: ``` \starttexdefinition loc [#1] \doifassignmentelse{#1} { % if an assignment, then parse and format accordingly \getparameters[loc][#1] % Was a section number specified? \doifdefined{locsec} { § \locsec } } { % otherwise, just print the input as-is #1 } \stoptexdefinition \def\DoIfPrefixElse#1#2{\ctxlua{commands.doifelse(string.find([==[#2]==],"^"..[==[#1]==]))}} \def\currentbtxloctext{\loc[sec=31]} \starttext § 31\blank%the raw text we expect \currentbtxloctext\blank%the text as produced by the macro \doifelse{\currentbtxloctext}{§ 31}{YES}{NOP}\blank% should output YES, but doesn't \DoIfPrefixElse{§}{\currentbtxloctext}{YES}{NOP}\blank% should output YES, but doesn't \stoptext ``` What am I missing here? Joey On Fri, Nov 26, 2021 at 11:57 AM Joey McCollum wrote:

Thanks! Invoking string.find(str,"^"..pre) is certainly much easier. This sort of thing would be a nice general-purpose helper function. Denis Maier and I should have a "wish list" of desired helpers and features (mostly related to bibliographies/publication support) ready for you (and Alan) sometime soon.

But for now, it looks like I still need to work out errors that arise when I pass a macro as the "str" input to be searched. I've defined a \loc macro that accepts an assignment and outputs a formatted string, and later, I want to check if this macro (after it has been fully expanded) starts with a certain prefix. A minimal (non-)working example follows:

```

\starttexdefinition loc [#1]

\doifassignmentelse{#1} {

% if an assignment, then parse and format accordingly

\getparameters[loc][#1]

% Was a section number specified?

\doifdefined{locsec} {

§ \locsec\btxcomma

}

} {

% otherwise, just print the input as-is

#1

}

\stoptexdefinition

\def\DoIfPrefixElse#1#2{\ctxlua{commands.doifelse(string.find("#2","^".."#1"))}}

\def\currentbtxloctext{\loc[sec=31]}

\starttext

\DoIfPrefixElse{§}{\currentbtxloctext}{YES}{NOP}

\stoptext ```

Lua is throwing an "invalid escape sequence near '"\l'" error, which is presumably because the macro \loc[sec=31] is not being expanded. How do I fix this?

Thanks!

Joey

On Fri, Nov 26, 2021 at 3:46 AM Hans Hagen via ntg-context < ntg-context@ntg.nl> wrote:

...

...

I wasn't aware of a general-purpose "doifstartswith" macro in ConTeXt (the \doifnextcharelse macro only works one character at a time, and

On 11/26/2021 7:42 AM, Joey McCollum via ntg-context wrote: the

...

\doifinstring macros may capture substrings that are not prefixes), and I'd like to develop one for something I'm working on. I've been trying to do this in Lua, as that seemed like the most natural approach. Normally, something like this would work fine as a foundation:

``` function isprefix(prefix, str) if string.sub(str, 1, string.len(prefix)) == prefix then return true end return false end ```

how about

if string.find(str,"^"..prefix) then

in:

\starttext

\def\DoIfPrefixElse#1#2{\ctxlua{commands.doifelse(string.find("#2","^".."#1"))}}

\DoIfPrefixElse{pre}{prefix}{YES}{NOP} \DoIfPrefixElse{pre}{suffix}{YES}{NOP}

\stoptext

utf strings are just sequences of bytes so matching works

when you want to do more in lua you can decide for

\startluacode interfaces.implement { name = "DoIfPrefixElse", arguments = { "argument", "argument" }, actions = function(pre,str) commands.doifelse(string.find(str,"^"..pre)) end } \stopluacode

\DoIfPrefixElse{pre}{prefix}{YES}{NOP} \DoIfPrefixElse{pre}{suffix}{YES}{NOP}

but in any case: make sure that you don't clash with built in ...

if needed i can make a set of fast(er) ones but someone has to collect a list of 'handy helpers' first

Hans

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I was afraid that might be the problem. I've described some of the intended purpose of this code near the end of the "Checking for a macro in a string without expanding it" thread on the mailing list, but I will get into more detail here. I'm working on a ConTeXt implementation of citation style language (CSL) locators, particularly for the SBL citation rendering (although the code could easily be adapted for use in general or with other bibliographic renderings). This would allow for a consistent, language-sensitive syntax that could be used within citations or in any part of a text and could accommodate changes in bibliographic style without requiring the user to reformat all their page number citations. In SBL style, for instance, volume, part, and page numbers are not prefixed by abbreviations like "vol.", "pt." and "p.", but in other styles, they might be. The locator syntax ``` \loc[vol=33,pt=1,p=86] ``` would be defined in the SBL rendering file to output ``` 33.1:86 ``` while in some other style, it might be defined to output ``` vol. 33, pt. 1, p. 86 ``` To accommodate the use of these macros within citations, I've added "loctext" (locator text) and "altloctext" (alternate locator text) arguments to the set of parameters used by the \cite macro, because in some bibliographic categories, different locators can be specified for different parts of a citation (e.g., one for a passage in an ancient text and another for the book reproducing it), and therefore cannot just be specified in the "righttext" parameter. So now we can do something like ``` \cite[lefttext={See},altloctext={1.3},loctext={8:223},righttext={for further details}][clementinehomilies] ``` to get See *The Clementine Homilies* 1.3 (*ANF *8:223) for further details. or ``` \cite[lefttext={See},loctext={\loc[p=8]},righttext={; but there are also contradictory statements, e.g. \loc[p=12].}][Doe:Title] ``` to get See Doe, *Title*, 8; but there are also contradictory statements, e.g. 12. The main problem is determining when to include a comma before printing the "loctext" and when not to include one. In the first example above, we don't want a comma between *ANF* and 8:223 (SBL style does not add a comma between a multivolume set abbreviation and a volume number), but in the second example, we do want one between *Title *and 8. Similarly, we want to remove the comma if the first locator in the loctext is a section marker (§) or paragraph marker (¶). This is why I want to check the beginning of the \currentloctext macro for the presence of a volume number (a number followed by a colon), a section mark, or a paragraph mark. While storing the locator parameters as btx parameters would allow for another solution to this problem, it would complicate defining the \loc macro in a way that would be suitable outside of citations or for multiple uses in the same citation (notice how a second \loc invocation occurs in the righttext of the second example above). Parsing the output of \loc seemed like the simplest solution, but as you've pointed out, it has its own difficulties. I'm inclined to try one of the TeX-based solutions you describe above to avoid complicating other things, but if my description of the intended use gives you any better ideas, please suggest them! Thanks again! Joey On Sat, Nov 27, 2021 at 1:44 PM Hans Hagen wrote:

On 11/27/2021 6:13 PM, Joey McCollum wrote:

...

All right, I think I've solved the expansion problem I described before: to ensure that the first input is expanded when it is passed to Lua, I have to pass it as [==[#1]==], not "#1". But the updated MWE below still does not seem to work, as the \DoIfPrefixElse macro is printing "NOP" instead of "YES":

```

\starttexdefinition loc [#1]

\doifassignmentelse{#1} {

% if an assignment, then parse and format accordingly

\getparameters[loc][#1]

% Was a section number specified?

\doifdefined{locsec} {

§ \locsec

}

} {

% otherwise, just print the input as-is

#1

}

\stoptexdefinition

\def\DoIfPrefixElse#1#2{\ctxlua{commands.doifelse(string.find([==[#2]==],"^"..[==[#1]==]))}}

...

\def\currentbtxloctext{\loc[sec=31]}

\starttext

\currentbtxloctext\blank

\DoIfPrefixElse{§}{\currentbtxloctext}{YES}{NOP}

\stoptext

```

Indeed, if I add a simple \doifelse equality check, it looks like the value I expect is not the same as what the macro produces, even though they look identical:

```

\starttexdefinition loc [#1] \doifassignmentelse{#1} { % if an assignment, then parse and format accordingly \getparameters[loc][#1] % Was a section number specified? \doifdefined{locsec} { § \locsec } } { % otherwise, just print the input as-is #1 } \stoptexdefinition

\def\DoIfPrefixElse#1#2{\ctxlua{commands.doifelse(string.find([==[#2]==],"^"..[==[#1]==]))}}

...

\def\currentbtxloctext{\loc[sec=31]}

\starttext § 31\blank%the raw text we expect \currentbtxloctext\blank%the text as produced by the macro \doifelse{\currentbtxloctext}{§ 31}{YES}{NOP}\blank% should output YES, but doesn't \DoIfPrefixElse{§}{\currentbtxloctext}{YES}{NOP}\blank% should output YES, but doesn't \stoptext

```

What am I missing here?

Expansion hell ... and i fear that you draw yourself into more and more trouble with this approach (which is why you don't find that kind of hackery in the core unless we're real desperate) so maybe try to explain what the real problem is that needs to be solved. Parsing tex is seldom a solution (at least not in context).

You can add:

\edef\Whatever{\currentbtxloctext}\meaning\Whatever \doifelse{\currentbtxloctext}{§ 31}{YES}{NOP}\blank

and see what comes back. Now, as always in tex, there's of course a solution because after all it's a programming language too (and at some point these solutions start looking so complex that one enters guru state)

\starttexdefinition loc [#1] \beginlocalcontrol \doifassignmentelse{#1} { \getparameters[loc][#1] \doifdefinedelse{locsec} { \endlocalcontrol § \locsec } { \endlocalcontrol } } { \endlocalcontrol #1 } \stoptexdefinition

a curious mix between a fully expanded result, using protected macros and hiding what tex does but hard to explain

Hans

----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl -----------------------------------------------------------------

Okay. So using this example as a template, I'd like to do the following: - define a general-purpose \loc macro that can be invoked in the main text (i.e., outside of citations) in the usual way; this one would correspond to \WhateverB above and would not remove punctuation preceding the macro. - separately define a \loctextloc macro that accepts the same input as \loc, but conditionally removes preceding punctuation based on variables set outside of this macro during the citation process (e.g., \btxsblshorthandbeforetextloc); this would correspond to \WhateverA above. - in the macro for typesetting the loctext btx parameter, redefine \loc to do what \loctextloc does, and then invoke \currentbtxloctext so that the \loc invocations it contains will be expanded like \loctextloc, as follows: \begingroup \def\loc\loctextloc \currentbtxloctext \btxcomma \endgroup Is this a ConTeXt-friendly way to do this? I'm attempted this now, but I have some errors to debug, and I'd like to know if this is even a feasible direction before I continue. Joey On Sun, Nov 28, 2021 at 5:39 AM Hans Hagen wrote:

On 11/28/2021 2:39 AM, Joey McCollum wrote:

...

I was afraid that might be the problem. I've described some of the intended purpose of this code near the end of the "Checking for a macro ...

Maybe play with:

\starttext

\def\WhateverA{\removeunwantedspaces\removepunctuation\space ¶ 1.23} \def\WhateverB{¶ 1.23}

foo bar, \WhateverA\ test foo bar, \WhateverB\ test

\stoptext

so, wrap ¶ into a macro

\def\MyParSymbol{\removeunwantedspaces\removepunctuation\space ¶}

Hans

----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl -----------------------------------------------------------------