11. Mathematical uses of lerfu strings

This chapter is not about Lojban mathematics, which is explained in Chapter 18, so the mathematical uses of lerfu strings will be listed and exemplified but not explained.

A lerfu string as mathematical variable:

11.1)    li .abu du li by. su'i cy.
    the-number a equals the-number b plus c
    a = b + c

11.2)    li .y.bu du li ma'o fy. boi xy.
    the-number y equals the number the-function f of x
    y = f(x)

Note the ``boi'' here to separate the lerfu strings ``fy'' and ``xy''.

A lerfu string as selbri (followed by a cmavo of selma'o MOI):

11.3)    le vi ratcu ny.moi le'i mi ratcu
    the here rat is-nth-of the-set-of my rats
    This rat is my Nth rat.

11.4)    ny.mai
    Nthly

11.5)    xy. xi ky.
    x sub k

11.6)    vei ny. [ve'o] lo prenu
    ( ``n'' ) persons

All the examples above have exhibited single lerfu words rather than lerfu strings, in accordance with the conventions of ordinary mathematics. A longer lerfu string would still be treated as a single variable or function name: in Lojban, ``.abu by. cy.'' is not the multiplication ``a x b x c'' but is the variable ``abc''. (Of course, a local convention could exist that made the value of a variable like ``abc'', with a multi-lerfu-word name, equal to the values of the variables ``a'', ``b'', and ``c'' multiplied together.)

There is a special rule about shift words in mathematical text: shifts within mathematical expressions do not affect lerfu words appearing outside

mathematical expressions, and vice versa.