Gdtyjr

Beamer's 'lecture' command has been a great way for me to have all my lecture notes in one document, but typeset only the segments that I need for any given day/week of class. Ultimately I would like to try and adapt this command to other document classes (currently it is very embedded in the 'beamer' class).

I would consider myself an advanced TeX user, but a novice when it comes to advanced programming (I've put together a few of my own `class' files, but nothing too advanced).

Here's what I found in 'beamerbasesection.sty':

%
% Lecture Definitions
%
newififbeamer@inlecture
beamer@inlecturetrue

newcommandbeamer@if@in@clist@TF[2]%
 defbeamer@if@in@clist@aux##1,#2,%
 expandafterexpandafterexpandafterifx
 expandafterexpandafterexpandafter@nil
 expandafterbeamer@if@in@clist@auxexpandafter,#1,,#2,@nil
 expandafter@secondoftwo
 else
 expandafter@firstoftwo
 fi


newcounterlecture
renewcommandthelecture@arabicc@lecture
letinsertlecturenumber=thelecture
newrobustcmd*lecture@dblargbeamer@lecture
longdefbeamer@lecture[#1]#2#3%
 beamer@savemode
 mode<all>%
 refstepcounterlecture%
 defbeamer@currentlecturelabel#3%
 @onelevel@sanitizebeamer@currentlecturelabel
 defbeamer@lecturename#2%
 defbeamer@shortlecturename#1%
 ifxbeamer@onlylecture@empty
 else
 expandafterbeamer@if@in@clist@TFexpandafterbeamer@onlylecture
 expandafterbeamer@currentlecturelabel%
 beamer@inlecturetrue%
 beamer@inlecturefalse%
 fi
 beamer@atbeginlecture
 beamer@resumemode

So how does this command work its magic? When I type includeonlylecturefoo, how does it know to grab only the text after lecture[]foo and before the next 'lecture' command? Thanks for any insight you can give!

Just for completeness I've included a minimal working example:

documentclass[]beamer

includeonlylecturefoo

begindocument
lecture[]notfoo1
beginframe
frametitleText1
This frame won't show.
endframe


lecture[]foo
beginframe
frametitleHello, World!
Greetings.
endframe


lecture[]notfoo2
beginframe
frametitleText2
This frame won't show either.
endframe
enddocument