# [NTG-context] A macro which gives a random name

Hans Hagen pragma at wxs.nl
Sat Apr 18 22:36:20 CEST 2015

On 4/18/2015 10:24 PM, Otared Kavian wrote:
> Hi again Wolfgang,
>
> Thanks to your hint, I could solve the problem…
> In case someone else would encounter a similar problem to solve, below is a macro which chooses an element from a list, it creates a control sequence (CS) containing that element and it keeps the CS until the next time the macro is invoked again to choose another element.
>
> Thanks again and best regards: OK
>
> %%%% begin choose-element.tex
> \setuprandomize[1989] % set a seed
>
> \starttext
>
> % here is a list from which a name is chosen
> \startluacode
> 	ListOfNames = {'F', 'G', 'u', 'v', 'W'}
> \stopluacode
>
> % this macro has two arguments:
> % the first argument is the control sequence name attached to Chosen,
> % the second argument is the name of the list from which something is chosen
> \define[2]\RandomChoice{%
> 	\setevalue{Chosen#1}{\ctxlua{%
> 		local listsize = \letterhash #2 ;
> 		local LName = #2 ;
> 		tex.print(LName[math.random(1,listsize)])}}}
>
> \dorecurse{10}{\RandomChoice{Function}{ListOfNames}%
> Give an example of a function $\ChosenFunction : {\Bbb R} \longrightarrow {\Bbb R}$ which has a derivative only at the origin, and such that ${\ChosenFunction}'(0) = 1$.\par \hairline\par}
>
> \stoptext
> %%%% end choose-element.tex

\starttext

\startluacode
local FunctionNames = { "G" , "W" }
local FunctionName  = FunctionNames[1]

function document.SetFunctionNames(list)
FunctionNames = utilities.parsers.settings_to_array(list)
end
function document.GetFunctionName(new)
if new then
FunctionName = FunctionNames[math.random(1,#FunctionNames)]
end
context(FunctionName)
end
\stopluacode

\def\SetFunctionNames[#1]{\ctxlua{document.SetFunctionNames("#1")}}
\def\NewFunctionName     {\ctxlua{document.GetFunctionName(true)}}
\def\GetFunctionName     {\ctxlua{document.GetFunctionName()}}

\SetFunctionNames[a,b,c,d]

\dorecurse{10}{
Give an example of a function
$\NewFunctionName : {\Bbb R} \longrightarrow {\Bbb R}$
which has a derivative only at the origin, and such that
$\GetFunctionName(0) = 1$.
\par \hairline\par
}

\stoptext

>> On 18 Apr 2015, at 19:23, Wolfgang Schuster <schuster.wolfgang at gmail.com> wrote:
>>
>>
>>> Am 18.04.2015 um 18:55 schrieb Otared Kavian <otared at gmail.com>:
>>>
>>> Hi everyone,
>>>
>>> In the example below I define a macro which chooses at random a name from a list of names. But I wonder whether this can be done in a more clever way without using a numerical macro created with math.random in Lua. The shortcoming of the macro below is that before hand I must know the nomber of elements in the list of names (for instance 5 in the example below), while it may happen that I need to create as many as random names that there are elements in the list, but sometimes I don’t know what is this number.
>>>
>>> Thanks for any insight and help.
>>> Best regards: OK
>>> %%%% begin random-names.tex
>>> \setuprandomize[2015] % set a seed
>>>
>>> \starttext
>>>
>>> \startluacode
>>> 	Name = {'F', 'G', 'u', 'v', 'W'}
>>> \stopluacode
>>>
>>> \define[3]\RandomName{%
>>> 	\setevalue{Named#1}{\ctxlua{tex.print(math.random(#2,#3))}}}
>>> \define\RandomFunctionName{\ctxlua{tex.print(Name[\NamedFunctionNumber])}}
>>>
>>> \dorecurse{10}{\RandomName{FunctionNumber}{1}{5}%
>>> Give an example of a function $\RandomFunctionName : {\Bbb R} \longrightarrow {\Bbb R}$ which has a derivative only at the origin, and such that $\RandomFunctionName(0) = 1$.\par \hairline\par}
>>>
>>> \stoptext
>>> %%%% begin random-names.tex
>>
>> You can access the size of your Name table with #Name but have to replace # with \letterhash when you use it in a TeX command because # is already taken for the TeX arguments.
>>
>> \starttext
>>
>> \startluacode
>> 	Name = {'F', 'G', 'u', 'v', 'W'}
>> \stopluacode
>>
>> \define\RandomFunctionName
>>   {\startlua
>>    local listsize    = \letterhash Name ;
>>    local randomvalue = math.random(1,listsize) ;
>>    context(Name[randomvalue])
>>    \stoplua}
>>
>> \dorecurse{10}{Give an example of a function $\RandomFunctionName : {\Bbb R} \longrightarrow {\Bbb R}$ which has a derivative only at the origin, and such that $\RandomFunctionName(0) = 1$.\par \hairline\par}
>>
>> \stoptext
>>
>> Wolfgang
>>
>> ___________________________________________________________________________________
>> If your question is of interest to others as well, please add an entry to the Wiki!
>>
>> maillist : ntg-context at ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
>> webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
>> archive  : http://foundry.supelec.fr/projects/contextrev/
>> wiki     : http://contextgarden.net
>> ___________________________________________________________________________________
>
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
>
> maillist : ntg-context at ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
> archive  : http://foundry.supelec.fr/projects/contextrev/
> wiki     : http://contextgarden.net
> ___________________________________________________________________________________
>

--

-----------------------------------------------------------------