VALWITH
Syntax
VALWITH ( expression, equation|equation list )
Implemented in iMath since version 2.2.0 or earlier.
Explanation
Try to find a value for the expression from any equations defined previously in the document, plus the equations given as the second argument. A value is expected to be a quantity, that is a number with optional units. If the expression cannot be reduced to a quantity, it will be reduced to numerical values as for as possible.
The expression will contain rational numbers, not floats, unless a conversion to a floating point number is required to obtain a quantity. This might be the case e.g. if the expression contains square roots of rational numbers. If you want to force a conversion to floats, use QUANTITY instead.
Example
EQDEF a = 3 x
EQDEF b = 2 x
EXDEF VALWITH(a + b, x = 7 %metre)
This will output 35 "m".