Listize, Unlistize and Show

At the moment, lists have to be built up using 57 and 58, which is rather annoying. Similarly, we can't actually do anything with a list once we've built it. We'd like some way of converting lists in the form 59 to and from the form [a, b, c]. This is done with 60 and 61. So 62 expands to

verbatim77#
Similarly, 63 takes the list [a, b, c] and expands out to 64. 65 is done with a Foldr.
 
The macro 66 is just a TEX hack with pattern matching. It would have been nice to use 67 for this, but that uses 68, which doesn't expand in the mouth. Oh well.
#TeXcode425#
This only works for nonempty lists --- 69 produces the singleton list 70. It also uses 71 as its end-of-list character, so lists with 72 in them have to be done by hand. You can't win them all. So
verbatim78#
produces #math159#[#tex2html_wrap_inline2697#[a, b, c][@#tex2html_wrap_inline2698#Unlistize#tex2html_wrap_inline2699#@]]. This is such a common construction that I've defined a macro 73 such that 74 expands out to
verbatim79#
For example, the equation
#math160#
Filter (Lessthan 1) [1, 2, 3] = #tex2html_wrap_indisplay2704# : #tex2html_wrap_indisplay2705#Foldr#tex2html_wrap_indisplay2706#@<1<#54#><1055>><#1050#>#tex2html_wrap_indisplay2707##tex2html_wrap_indisplay2708#! :}#tex2html_wrap_indisplay2709#1 ;SPMlt; < <438>>[1, 2, 3]  

was generated with
verbatim80#
Many of the examples in this article were typeset this way.