I get confused behaviour if I use something like 1’3 or 1’6 when units are set to mm.
A line set to 1’3 long comes out at 307.8 mm - one foot, plus 3mm.
1’6 becomes 310.8mm
10 1/2" becomes 10.5mm
1’ 3 1/2" becomes 308.3mm - one foot plus 3.5mm, in spite of the
" (inch) mark.
I think this is just a muddle. It recognises the unit characters (foot and inch marks, separately) but ignores a mixture of the two in a bizarre and confusing way, treating anything after the first mark as if no units mark is later appended*.
While this may be sort of logical, I think it is wrong, or at the very least, half-hearted and confused.
Surely it should either say ‘invalid length entered’ or calculate it properly. If you aren’t paying full attention, and just type in the value and get no feedback, you’ll THINK you have entered a valid and correct size, but it will be in mixed units and wrong.
And can’t see that it would be difficult to fix. There must already be a function to calculate decimal inches from feet, inches, and fractions: why can’t it be invoked whatever the user units are set to, by the code that parses lengths and treats some as invalid? The input is ‘valid’ as in meaningful, just calculated incorrectly.
[*Note from above. It does NOT ignore the inch mark if there is no fraction, I now find]
It’s even more confused than I thought.
As I said above, 1’3 is treated as one foot plus 3mm.
But 1’3" comes out at 381.0 mm = 15 x 2.54mm.
This is even more bizarre than I thought.
I’d call this a bug, however long standing it may be.