Feature request

[Andy]

A couple of requests to make it more functional.

First (easy): add a notes window for each custom equation. It is
nice to have a few reference notes (common variable values, hints on
the formula use, etc) for some engineering formulas.

Second (little harder): add the ability to add descriptions to
variables in the input pane. ie - if you had an area formula of
L*W=A, rather than simply L, W and A, it would be nice to add a few
words of text in front and behind each variable so they would be
"Length - L (ft)", "Width - W (ft)", and "Area - A (sf)". I realize
that you might be able to this to some extent by writing the formula
as Length*Width but this wouldn't work very well with variables such
as Wetted Perimeter or Coefficient of Friction.

Third (tough, maybe): nested equations in the same pane. Many
problems are solved by sets of equations. It would really be great if
several equations could exist and be solved through iterations. Below
is an example of concrete pavement calcs

Basic formulas:
Abar=Pi()*(No/8)**2/4
Bars=Round(A*W/Abar)
Mr=2.3*fc**(2/3)
A=L*Cf*wt*h/(24*2/3*fy)

Variables with descriptions:
Modulus of Rupture Mr: 500
Cmprssve Strength (psi) fc: 3,205.2599
Area of Steel Rqrd (sqin) A->0.0306
Distance between Joints (ft) L: 15
Coefficient-Subgrade Resistance Cf: 1.5
Weight of Concrete (pcf) wt: 145
Pavement Thickness (in) h: 9
Steel Yield Strength (psi) fy: 60000

Bar Size No: 3
Single Bar Area (in2) Abar->0.1104
Slab Width (ft) W:36
Total Required Bars->10.0000


Notes:
Area of steel required per foot of slab width
Bar Size No: 3
Single Bar Area (in2) =0.1104

[hoymoon]

Hello Andy,

Thank you for your interest in Formulaic, and for your great
suggestions.

1) The "notes" idea is already on our list for a future release of
Formulaic. The biggest challenge with an iPhone app isn't so much
programming a new feature; it is providing a clever way to integrate
and access it without cluttering the user interface. But we've already
identified a couple of possibilities.

2) The variable documentation suggestion is (kind of) already in
Formulaic. Variable names start with a letter (a to z, or A to Z), and
can then continue with letters, digits (0 to 9) or an underscore (_).
In some of the sample equations, we used a convention similar to the
following:

length_cm * 2.54 = length_inch

Using such a convention to specify units for variables can make an
equation a lot easier to understand as you correctly point out.

3) Your multiple-linked-equation suggestion is also (kind of) already
in Formulaic. From the outset, we identified that some variables might
be used in multiple equations, such as "Abar" in your example. To
address this, Formulaic supports both "local" and "global" variables.
Local variables (those which start with a lower-case letter a to z)
are private to a single equation, and their values can only be
accessed and changed while working with the equation in which they are
defined. Global variables (those that start with an upper-case letter
A to Z) are shared amongst all equations, and their value can be used
or changed in any equation which refers to that variable. You can of
course mix global and local variables in one equation to fine-tune.

You can group several equations you'll be using together into a "User
Category" you define. When you're working with one equation, and you
tap top left to return to the list of equations, Formulaic remembers
the point to which you scrolled in the list of equations, so you can
quickly switch to another one.

With both of your suggestions (2) and (3), we acknowledge that the
existing functionality in Formulaic might not be exactly what you had
in mind, but at least there's something already in Formulaic to get
you started. We will of course keep those suggestions on our wish list
too, if only to ensure that we continue thinking about how to better
support your suggestions.

Kind regards,
Hoy Moon