Expressions

Every numeric field takes arithmetic, not just a number. Dimensions in the docket, the X and Y fields for a point, extrude distances, blend sizes, and the editor that opens on a canvas dimension.

Type 25.4 * 2 into a dimension and press Enter, and the field commits 50.80.

Grammar

Standard precedence. Tightest binding last:

expr   :=  term (('+' | '-') term)*
term   :=  unary (('*' | '/' | '%') unary)*
unary  :=  ('-' | '+') unary | power
power  :=  atom ('^' unary)?
atom   :=  number | '(' expr ')' | name '(' args ')' | name

^ is right associative, so 2^3^2 is 512 rather than 64.

Operators

+ - * /	The usual
%	Remainder
^	Power
( )	Grouping

Constants

pi	3.14159...
tau	2 pi
e	2.71828...

Functions

sqrt(x) abs(x)
floor(x) ceil(x) round(x)
sin(x) cos(x) tan(x)	Argument in degrees
asin(x) acos(x) atan(x)	Result in degrees
min(a, b, ...) max(a, b, ...) hypot(a, b, ...)	Any number of arguments

Degrees throughout, matching what the angle fields display. sin(30) is 0.5.

Units

A trailing mm, deg, or ° is stripped and ignored. 40mm is 40. This exists so pasting a value that carries its unit does the obvious thing, rather than as a unit conversion: there is no unit system to convert between, and everything is millimetres and degrees.

To work from inches, do the conversion yourself in the field: 1.5 * 25.4.

Committing

Enter	Evaluate and commit
Esc	Revert to the stored value and leave the field
Click away	Commit if valid, revert if not

A field that cannot be parsed turns red and keeps focus on Enter, so a typo is corrected in place rather than silently swallowed. Clicking away from a bad expression abandons it and the field returns to the value the model holds. Nothing is ever committed half-parsed.

The dimension editor that opens on a canvas annotation shows a live = 20.00 preview underneath as you type, so you can see the result before committing.

Names

A bare name resolves against the document's parameters first and the built-in constants after. Define width = 40 in the table and width / 2 works in any dimension, extrude distance or blend size.

A parameter cannot be named after a constant, a function, or the unit suffixes mm and deg, since those already mean something here.

What is stored

A field driven by a parameter keeps the expression as well as the value, and shows the expression when you focus it. A field carrying plain arithmetic keeps it the same way, so 25.4 * 2 is still 25.4 * 2 when you go back to it.

Typing a plain number over either drops the expression.

Point X and Y fields are the exception: they take arithmetic, keep nothing, and show the number. They are solver output, so a stored expression would be overwritten on the next solve.

A note on safety

This is a hand-written parser, never the browser's own code evaluator. A document read from disk or produced by the importer cannot smuggle code into a numeric field.