Remove failed Solve[] attempts

Question

I can't figure how to replace a failed evaluation with a null value.

I am very new to Mathematica.

I have an equation that are being processed using the Solve[] function and I then need to forward the results to other steps in my process. Some of the equations don't have solutions. This is desired and I want to eliminate those possibilities.

After generating a list with all the solutions I process that list like this:

SillySyntax[Rule_] = Quiet[x /. Rule];
Quiet[Curve = Table[SillySyntax[Curves[[i]]], {i, 5}]]

This works fine, but sometimes when errors such as the following happen they break my workflow by not putting a null in there. Instead leaving a ghost of an equation. This is not desired because I know a priori that these errors mean that the system is not physical. How can I remove these aberrations and ensure that SillySyntax will output only numbers or empties.

Greater::nord: "Invalid comparison with 0.347148 -1.5103810834566311` I"

Answer 1

I'm pretty sure your error message comes from something different. Anyway, what happens if you use for instance such a solve function?

solveMe[z_] := 
 Module[
  {solution = Solve[x^2 + y^2 == z^2 && y > x > 0, {x, y}, Integers]},
  If[solution =!= {},
    {x, y} /. solution,
    solution
  ]
]

If the solution is empty, it just returns the {}. Otherwise, it extracts the numbers of the solution. Therefore:

Table[solveMe[z],{z,30}]
(*
{{},{},{},{},{{3,4}},{},{},{},{},{{6,8}},{},{},{{5,12}},{},{{9,12}},
{},{{8,15}},{},{},{{12,16}},{},{},{},{},{{7,24},{15,20}},{{10,24}},{},
{},{{20,21}},{{18,24}}}
*)

Since you mentioned Quiet: If you want a function which returns something else when a message is generated, you can use Check.

f[e_] := Quiet[Check[1/e, "Hola seniorita"]]
f[1]
f[0]

(*
  1
  "Hola seniorita"
*)

Here we catch the message that is generated when we divide by 0 and return a different result.