TEACH MAKESENT                             Steven Hardy, November 1982

This file follows on from TEACH ISASENT. The next file in the sequence is
TEACH PARSESENT. This file can be skipped without serious loss. Unless you
have the time and the inclination to work through THIS file, then go on to
TEACH PARSESENT immediately.

-- MAKING SENTENCES ----------------------------------------------------

A simple systematic change can be made to the ISA programs to turn them into
MAKE programs which generate rather than recognize them. The 'lexical
recognizers' are easiest to convert. Instead of:

    define isafoo(word) -> result;
        if member(word, [...]) then
            true -> result
        else
            false -> result
        endif
    enddefine;

We would have:

    define makefoo() -> result;
        oneof([...]) -> result
    enddefine;

Notice that MAKEFOO doesn't have any parameters and its result is a word and
not a truth value.

The 'syntax procedures' are slightly harder to modify. Suppose a syntax
procedure has three main options. That is it looks like:

    define isafoo(list) -> result;
        if list matches [...] then
            true -> result
        elseif list matches [...] then
            true -> result
        elseif list matches [...] then
            true -> result
        else
            false -> result
        endif
    enddefine;

The MAKE form of this will have the overall pattern:

    define makefoo() -> result;
        vars option; oneof([1 2 3]) -> option;
        if option = 1 then
            [...] -> result
        elseif option = 2 then
            [...] -> result
        else
            [...] -> result
        endif
    enddefine;

The various lists assigned to the result will be modified forms of the
original pattern. The pattern:

    [??x:isafoo ?y:isabaz ??z:isagrum]

will be turned into

    [^^(makefoo()) ^(makebaz()) ^^(makegrum())]