This is by far the best MATHCAD substitute for iPad users. The GUI is not intuitive if you are a MATHCAD user, but it works reasonably well after you become accustomed to it. A guide for the GUI with multiple examples would be helpful. The online guide is helpful, but could be improved with examples. I am not a Python user, so I need better guidance on the GUI without the need for Python. The images on the app store are helpful to see what is possible; more like that would help.
Unlike MATHCAD, redefining a variable can cause issues. MathCanvas does not have the left-right, top-down calculation hierarchy of MATHCAD. Also if you use a defined variable name in some functions like solve, it gets confused. Using the variable name N will confuse the N() evaluation function. These are generally not issues in MATHCAD.
The app appears not to have built in constants like π, so you need to define all variables before you use them in an equation. Its units appear to be SI, but it includes only basic units. Others like Pascals, μm, etc. need to be defined in basic units. It has a units conversion function, but it is not global and I am still experimenting with it. You can mix units like MATHCAD if you define variables as noted above. MATHCAD costs $1000.00. So, MathCanvas is really amazing!
I highly recommend this app for numerical and symbolic calculations on iPads. I do have a couple of recommendations: it needs an option to turn off the little popups that come up every time you enter a new variable or do a calculation. Not only do they persist until you turn each one off, they reappear every time you open the document. It also needs a better select and copy for iPad. I cannot select a complete expression to paste into another equation. Hopefully, updates will include these items.