> Numerical values such as line lengths or indents or positions > are stored internally in (device-dependent) "basic resolution > units". The formatter accepts input in other units, but > converts these to basic units when it encounters them, and > reading back a register returns its contents in these units. > If you want to use one of these values again as input, you > must specify "u" as unit, to tell troff not to apply any > default unit conversion. Example: > > .ll 15c \" 15 cm is converted to internal units > .nr xx \n[.l]/2 \" do some arithmetic > .ll \n[xx]u \" use the computed value as line length
Thank you very much! Now I realise what I was misreading in the manual, namely: > The default scaling indicator is ‘m’. Which was referring to input, not output. > You can also increment or decrement registers. E.g., > > .in +1c > .ll -2c > > This is perhaps what you're trying to achieve. Thanks. I gather that's relative to its last value, whereas I'm trying to change it relative to its initial value, hence storing that value in a variable right away, and subtracting things from that later on. Thanks, Zoe.
