#### 6.8.10.5 Information about Compositions

The functions in this section are actual functions; they compose their
arguments according to the current language and other display modes,
then return a certain measurement of the composition as an integer.

The `cwidth`

function measures the width, in characters, of a
composition. For example, ‘`cwidth(a + b)`’ is 5, and
‘`cwidth(a / b)`’ is 5 in Normal mode, 1 in Big mode, and 11 in
TeX mode (for ‘`{a \over b}`’). The argument may involve
the composition functions described in this section.

The `cheight`

function measures the height of a composition.
This is the total number of lines in the argument’s printed form.

The functions `cascent`

and `cdescent`

measure the amount
of the height that is above (and including) the baseline, or below
the baseline, respectively. Thus ‘`cascent(``x`) + cdescent(`x`)’
always equals ‘`cheight(``x`)’. For a one-line formula like
‘`a + b`’, `cascent`

returns 1 and `cdescent`

returns 0.
For ‘`a / b`’ in Big mode, `cascent`

returns 2 and `cdescent`

returns 1. The only formula for which `cascent`

will return zero
is ‘`cvspace(0)`’ or equivalents.