% language=uk

\environment math-layout

\startcomponent math-input

\startchapter[title=Inputting math]

\startsection[title=Collapsing]

When in text mode you enter a combination of combining accent and character, a
composed character is assumed and often you then get one shape in your document.
A similar feature is available in math mode. After some discussion and analysis
of the potential clashes and confusion (thanks to Aditya Mahajan) we settled on a
combination of methods: so called math lists entries that we entered in the
character database and|/|or so called special sequences that are part of
\UNICODE. In the next tables we use \type {ml} for math list and \type {sp} for
specials. Collapsing mode \type {1} only uses the specials, while \type {2} first
checks the specials and then the math lists, and \type {3} does the reverse.

In the database you can find this (a few fields have been omitted):

\starttyping
[0x2260] = {
    adobename   = "notequal",
    category    = "sm",
    description = "NOT EQUAL TO",
    mathlist    = { 0x2F, 0x3D },
    mathspec    = {
        {
            class = "relation",
            name  = "neq",
        },
        {
            class = "relation",
            name  = "ne",
        },
    },
    specials    = { "char", 0x3D, 0x338 },
    unicodeslot = 0x2260,
}
\stoptyping

and

\starttyping
[0x2261] = {
    adobename      = "equivalence",
    category       = "sm",
    description    = "IDENTICAL TO",
    mathclass      = "relation",
    mathextensible = "h",
    mathname       = "equiv",
    mathlist       = { 0x3D, 0x3D },
    unicodeslot    = 0x2261,
}
\stoptyping

Here are a few examples:

\def\Test#1%
  {\NC \bf \type{$#1$}
   \NC \setupmathematics[collapsing=0] $#1$
   \NC \setupmathematics[collapsing=1] $#1$
   \NC \setupmathematics[collapsing=2] $#1$
   \NC \setupmathematics[collapsing=3] $#1$ \NC \NR}

\starttabulate[|c|cp|cp|cp|cp|]
    \NC \BC \ttbf 0 \BC \ttbf 1 (sp) \BC \ttbf 2 (sp ml) \BC \ttbf 3 (ml sp) \BC \NR
    \Test{==}
    \Test{/=}
    \Test{>=}
\stoptabulate

A complete list of collapses can be generated after loading one of the tracing
modules:

\startbuffer
\usemodule[math-ligatures]
\stopbuffer

\typebuffer \getbuffer

This provides the command:

\startbuffer
\showmathligatures
\stopbuffer

\typebuffer

which gives:

\start \switchtobodyfont[8pt] \getbuffer \stop

\stopsection

\stopchapter

\stopcomponent