Android Question generat maths question

Brian Dean said:

Okay - I don't mind stealing other people's ideas, so encouraged by @Farzam's "Like" I used @emexes suggestion about division and @aeric's function to replace the operator signs and added a random fourth element to the equation and came up with the following . . .

B4X:

Private Sub generate As String
    Dim digit() As String = Array As String("2", "3", "4", "5", "6", "7", "8", "9")
    Dim operator() As String = Array As String(" + ", " - ", " * ", " / ")
    Dim e As B4XEval
    e.Initialize(Me, "eval")
    Dim equation As String
    Dim check As Float
    Dim result As Int
    Do Until (result > 0) And (result < 100)
        equation = digit(Rnd(0, 8)) & operator(Rnd(0, 3)) & digit(Rnd(0, 8)) & operator(Rnd(0, 3)) & digit(Rnd(0, 8))
        If (Rnd(1, 3) = 2) Then equation = equation & operator(Rnd(2, 4)) & digit(Rnd(0, 8))
        check = e.Eval(equation)                       ' Calculate float value
        result = Round(check)                          ' Convert to integer value
        If (Abs(result - check) > 0) Then result = 0   ' Discard if not an integer result
    Loop
    equation =  equation.Replace("*", "x").Replace("/", "÷")
    Log("Equation = " & equation & " = " & result)
    Return equation  
End Sub

Here are some sample results . . .



These results don't look too bad, but there are still snags. Note that I limit the result of the calculation to 99 - that seems a good idea. I allow only one division sign - allowing more than one can produce rather enigmatic equations which is not what we want here, I suspect. Also this simple code produces terms like "4 + 3 - 2 / 2" - that is division by oneself - more often than one might expect. So perhaps still more work to be done.

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emexes said:

with two numbers 1..10 (and one operator) we can make all numbers up to 21
with three numbers 1..10 (and two operators) we can make all numbers up to 110
with four numbers 1..10 (and three operators) we can make all numbers up to 460

Still waiting for the next result. Seems to be exponential runtime.

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Daestrum said:

Log($"Answer = ${answer.As(Int)}"$)

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Dim exp As String = "7 / 0"
Log(NumberFormat(e.Eval(exp), 1, 0))

∞

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