Android Question generat maths question

[Farzam]

hello
I want to make a math question by coding in the form of 3 numbers in math operations...
For example: 3-10*6 , the output should not be negative
Or: 10*2+5 , Priority is important .

But I don't want the result to be a negative number, or to observe the priority of the equation in the equations

 

[Erel]

Not sure that I understand...

The correct output of 3-10*6 is -57

You can use this class to calculate such expressions: https://www.b4x.com/android/forum/threads/b4x-eval-expressions-evaluator.54629/#content

 

[aeric]

Maybe the OP means
Log(abs(e.Eval("3-10*6")))
?

 

[DonManfred]

Maybe the OP means

It would have been better if the OP would have posted the expected results too.

 

[Shelby]

Reverse the order of all characters.
6*10-3
results=57? or 42? (not negative)
I'm just being silly without using parentheses.

 

[Farzam]

Maybe the OP means
Log(abs(e.Eval("3-10*6")))
?

Well, now, in this calculation, first multiplication is calculated and then subtraction...
The output is -57

I don't want the output to be a negative number
With this command, I do the operation with 2 numbers, now I want it to be 3 numbers

Sub GenerateQuestion1(minValue As Int,maxValue As Int) As QuestionModel
    Dim operations() As String = Array As String("+", "-", "x", "÷")
    Dim operation As String = operations(Rnd(0, operations.Length))
    Dim a, b,answer As Int
    Select operation
        Case "+"
            a = Rnd(minValue, maxValue)
            b = Rnd(minValue, maxValue)
            answer = a + b
        Case "-"
            a = Rnd(minValue, maxValue)
            b = Rnd(minValue, a + 1)
            answer = a - b
        Case "x"
            a = Rnd(minValue, maxValue)
            b = Rnd(minValue, maxValue)
            answer = a * b
        Case "÷"
            b = Rnd(minValue, maxValue)
            answer = Rnd(minValue, maxValue)
            a = answer * b
    End Select
    
    L_Quzie.Text = a & " " & operation & " " & b & " = ?"

    AnsverNum=answer

    
End Sub

 

[Farzam]

Not sure that I understand...

The correct output of 3-10*6 is -57

You can use this class to calculate such expressions: https://www.b4x.com/android/forum/threads/b4x-eval-expressions-evaluator.54629/#content

My problem is not the output, I want to create a mathematical equation with 3 or 4 numbers...
Like software: Quick Brain
For example: 3+5*2-10

 

[aeric]

I don't want the output to be a negative number

Log(abs(e.Eval("3-10*6")))

The above code output 57.

Please check Erel's answer.

 

[aeric]

For example: 3+5*2-10

Log(e.Eval("3+5*2-10")) ' output = 3

Log(e.Eval("3 + 5 * 2 - 10 =")) ' output = 3

 

[emexes]

I want to create a mathematical equation with 3 or 4 numbers...
For example: 3+5*2-10

Is this in the ballpark of what you're trying to create?
(creating numbers from 1 to 100 using exactly three numbers from 1 to 10)

Waiting for debugger to connect...
Program started.
1 = ((1+1)-1)
2 = ((1+1)*1)
3 = ((1+1)+1)
4 = ((1+1)+2)
5 = ((1+1)+3)
6 = ((1+1)*3)
7 = ((1+1)+5)
8 = ((1+1)*4)
9 = ((1+1)+7)
10 = ((1+1)*5)
11 = ((1+1)+9)
12 = ((1+1)*6)
13 = (1+(2*6))
14 = ((1+1)*7)
15 = ((1+2)*5)
16 = ((1+1)*8)
17 = (1+(2*8))
18 = ((1+1)*9)
19 = (1+(2*9))
20 = ((1+1)*10)
21 = ((1+2)*7)
22 = ((1+10)*2)
23 = ((3*8)-1)
24 = ((1+2)*8)
25 = (1+(3*8))
26 = ((3*9)-1)
27 = ((1+2)*9)
28 = ((1+3)*7)
29 = ((3*10)-1)
30 = ((1+2)*10)
31 = (1+(3*10))
32 = ((1+3)*8)
33 = ((1+10)*3)
34 = ((5*7)-1)
35 = ((1+4)*7)
36 = ((1+3)*9)
37 = (1+(4*9))
38 = (2+(4*9))
39 = ((4*10)-1)
40 = ((1+3)*10)
41 = (1+(4*10))
42 = ((1+5)*7)
43 = (1+(6*7))
44 = ((1+10)*4)
45 = ((1+4)*9)
46 = (1+(5*9))
47 = ((6*8)-1)
48 = ((1+5)*8)
49 = ((5*10)-1)
50 = ((1+4)*10)
51 = (1+(5*10))
52 = (2+(5*10))
53 = ((6*9)-1)
54 = ((1+5)*9)
55 = ((1+10)*5)
56 = ((1+6)*8)
57 = (1+(7*8))
58 = ((6*10)-2)
59 = ((6*10)-1)
60 = ((1+5)*10)
61 = (1+(6*10))
62 = ((7*9)-1)
63 = ((1+6)*9)
64 = ((1+7)*8)
65 = (1+(8*8))
66 = ((1+10)*6)
67 = ((7*10)-3)
68 = ((7*10)-2)
69 = ((7*10)-1)
70 = ((1+6)*10)
71 = (1+(7*10))
72 = ((1+7)*9)
73 = (1+(8*9))
74 = (2+(8*9))
75 = ((3*5)*5)
76 = (4+(8*9))
77 = ((1+10)*7)
78 = ((8*10)-2)
79 = ((8*10)-1)
80 = ((1+7)*10)
81 = ((1+8)*9)
82 = (1+(9*9))
83 = (2+(9*9))
84 = ((2*6)*7)
85 = (4+(9*9))
86 = ((9*10)-4)
87 = ((9*10)-3)
88 = ((1+10)*8)
89 = ((9*10)-1)
90 = ((1+8)*10)
91 = (1+(9*10))
92 = (2+(9*10))
93 = (3+(9*10))
94 = (4+(9*10))
95 = (5*(9+10))
96 = ((2*6)*8)
97 = ((10*10)-3)
98 = ((2*7)*7)
99 = ((1+10)*9)
100 = ((1+9)*10)
Program terminated (StartMessageLoop was not called).

 

[emexes]

Is this in the ballpark of what you're trying to create?
(numbers from 1 to 100 using exactly three numbers from 1 to 10)

Waiting for debugger to connect...
Program started.
1 = ((1+1)-1)
2 = ((1+1)*1)
3 = ((1+1)+1)
4 = ((1+1)+2)
5 = ((1+1)+3)
6 = ((1+1)*3)
7 = ((1+1)+5)
8 = ((1+1)*4)
9 = ((1+1)+7)
10 = ((1+1)*5)
11 = ((1+1)+9)
12 = ((1+1)*6)
13 = (1+(2*6))
14 = ((1+1)*7)
15 = ((1+2)*5)
16 = ((1+1)*8)
17 = (1+(2*8))
18 = ((1+1)*9)
19 = (1+(2*9))
20 = ((1+1)*10)
21 = ((1+2)*7)
22 = ((1+10)*2)
23 = ((3*8)-1)
24 = ((1+2)*8)
25 = (1+(3*8))
26 = ((3*9)-1)
27 = ((1+2)*9)
28 = ((1+3)*7)
29 = ((3*10)-1)
30 = ((1+2)*10)
31 = (1+(3*10))
32 = ((1+3)*8)
33 = ((1+10)*3)
34 = ((5*7)-1)
35 = ((1+4)*7)
36 = ((1+3)*9)
37 = (1+(4*9))
38 = (2+(4*9))
39 = ((4*10)-1)
40 = ((1+3)*10)
41 = (1+(4*10))
42 = ((1+5)*7)
43 = (1+(6*7))
44 = ((1+10)*4)
45 = ((1+4)*9)
46 = (1+(5*9))
47 = ((6*8)-1)
48 = ((1+5)*8)
49 = ((5*10)-1)
50 = ((1+4)*10)
51 = (1+(5*10))
52 = (2+(5*10))
53 = ((6*9)-1)
54 = ((1+5)*9)
55 = ((1+10)*5)
56 = ((1+6)*8)
57 = (1+(7*8))
58 = ((6*10)-2)
59 = ((6*10)-1)
60 = ((1+5)*10)
61 = (1+(6*10))
62 = ((7*9)-1)
63 = ((1+6)*9)
64 = ((1+7)*8)
65 = (1+(8*8))
66 = ((1+10)*6)
67 = ((7*10)-3)
68 = ((7*10)-2)
69 = ((7*10)-1)
70 = ((1+6)*10)
71 = (1+(7*10))
72 = ((1+7)*9)
73 = (1+(8*9))
74 = (2+(8*9))
75 = ((3*5)*5)
76 = (4+(8*9))
77 = ((1+10)*7)
78 = ((8*10)-2)
79 = ((8*10)-1)
80 = ((1+7)*10)
81 = ((1+8)*9)
82 = (1+(9*9))
83 = (2+(9*9))
84 = ((2*6)*7)
85 = (4+(9*9))
86 = ((9*10)-4)
87 = ((9*10)-3)
88 = ((1+10)*8)
89 = ((9*10)-1)
90 = ((1+8)*10)
91 = (1+(9*10))
92 = (2+(9*10))
93 = (3+(9*10))
94 = (4+(9*10))
95 = (5*(9+10))
96 = ((2*6)*8)
97 = ((10*10)-3)
98 = ((2*7)*7)
99 = ((1+10)*9)
100 = ((1+9)*10)
Program terminated (StartMessageLoop was not called).

 

[aeric]

what you're trying to create?

I guess the OP is trying to create a quiz like game/app for education purpose.
I think it should have the function to generate 2 or 3 random numbers and 1 or 2 random operators.

 

[emexes]

I guess the OP is trying to ...

Don't you just love these open-ended questions?

Anyway, I've gotten as far as:

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. Although, to be fair, my code is pretty lax, aka: simple and programmer friendly.

 

[aeric]

Here is my attempt. Of course here we don't like speculate.

Sub Play
    Dim e As B4XEval
    e.Initialize(Me, "Eval")
    
    Dim q1 As String = GenerateExpression(1, 10)
    Log(q1)
    Dim q2 As String = ConvertExpressionToMath(q1)
    Log(q2)
    
    Dim answer As Int = NumberFormat(e.Eval(q1), 1, 0)
    Log($"Answer = ${answer}"$)
    
    Log("Convert to absolute value")
    Log($"New Answer = ${Abs(answer)}"$)
End Sub

Sub GenerateExpression (minValue As Int, maxValue As Int) As String
    Dim Operators(4) As String = Array As String("+", "-", "*", "/")
    Dim expression As String
    Dim NumofOperands As Int = Rnd(2, 5)
    Dim Operands(NumofOperands) As Int
    For i = 0 To NumofOperands - 1
        If i > 0 Then
            expression = expression & " " & Operators(Rnd(0, Operators.Length))
        End If
        Operands(i) = Rnd(minValue, maxValue + 1)
        'Log($"${i}=${Operands(i)}"$)
        expression = expression & " " & Operands(i)
    Next
    Return expression
End Sub

Sub ConvertExpressionToMath (Expression As String) As String
    Return Expression.Replace("*", "x").Replace("/", "÷") & " = ?"
End Sub

Output logs:

 3 - 8 * 9 + 3
 3 - 8 x 9 + 3 = ?
Answer = -66
Convert to absolute value
New Answer = 66

 

[Brian Dean]

Here is another suggestion :

Private Sub generate As String
    Dim digit() As String = Array As String("1", "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 result, discards As Int
    Do Until (result > 0)
        equation = digit(Rnd(0, 9)) & operator(Rnd(0, 3)) & digit(Rnd(0, 9)) & operator(Rnd(0, 3)) & digit(Rnd(0, 9))
        result = e.Eval(equation)
        If (result < 1) Then discards = discards + 1
    Loop
    Log("Equation = " & equation & " = " & result & ";  Discards = " & discards)
    Return equation
End Sub

. . . and some results . . .

Equation = 7 + 9 + 4 = 20; Discards = 0
Equation = 9 - 8 + 9 = 10; Discards = 0
Equation = 7 - 2 + 4 = 9; Discards = 0
Equation = 5 + 4 - 3 = 6; Discards = 2
Equation = 9 * 5 * 5 = 225; Discards = 0
Equation = 8 + 2 + 7 = 17; Discards = 0
Equation = 7 + 3 + 4 = 14; Discards = 0
Equation = 3 * 9 * 5 = 135; Discards = 1
Equation = 3 * 1 + 8 = 11; Discards = 0
Equation = 7 * 2 - 1 = 13; Discards = 0

Of course, we have not introduced division here; that would be much more complicated, assuming we are looking for integer results.

 

[emexes]

we have not introduced division here; that would be much more complicated

That's what I expected too, but turned out to not be that bad:

Case 4:    'division
    If V(J) = 0 Then    'exclude division-by-zero
        OkFlag = False
    Else If V(I) Mod V(J) <> 0 Then    'exclude non-integer results
        OkFlag = False
    Else
        MM(II) = "(" & M(I) & "/" & M(J) & ")"    'the resultant math
        VV(II) = V(I) / V(J)    'and corresponding resultant value
        If VV(II) < 0 Then OkFlag = False    'exclude negative results
    End If

 

[Daestrum]

@aeric I changed your play sub a little bit

Sub Play
    Dim e As B4XEval
    Dim q1 As String
    Dim answer As Double = -1
    e.Initialize(Me, "Eval")
    Do While answer < 0 Or (answer <> answer.As(Int))
        q1 = GenerateExpression(1, 10)
        answer = e.Eval(q1)
    Loop
    Log(q1)
    Log(NumberFormat(e.Eval(q1), 1, 0))
    Log($"Answer = ${answer.As(Int)}"$)
End Sub

It should produce only positive integer results

 

[Farzam]

Here is my attempt. Of course here we don't like speculate.

Sub Play
    Dim e As B4XEval
    e.Initialize(Me, "Eval")
   
    Dim q1 As String = GenerateExpression(1, 10)
    Log(q1)
    Dim q2 As String = ConvertExpressionToMath(q1)
    Log(q2)
   
    Dim answer As Int = NumberFormat(e.Eval(q1), 1, 0)
    Log($"Answer = ${answer}"$)
   
    Log("Convert to absolute value")
    Log($"New Answer = ${Abs(answer)}"$)
End Sub

Sub GenerateExpression (minValue As Int, maxValue As Int) As String
    Dim Operators(4) As String = Array As String("+", "-", "*", "/")
    Dim expression As String
    Dim NumofOperands As Int = Rnd(2, 5)
    Dim Operands(NumofOperands) As Int
    For i = 0 To NumofOperands - 1
        If i > 0 Then
            expression = expression & " " & Operators(Rnd(0, Operators.Length))
        End If
        Operands(i) = Rnd(minValue, maxValue + 1)
        'Log($"${i}=${Operands(i)}"$)
        expression = expression & " " & Operands(i)
    Next
    Return expression
End Sub

Sub ConvertExpressionToMath (Expression As String) As String
    Return Expression.Replace("*", "x").Replace("/", "÷") & " = ?"
End Sub

Output logs:

 3 - 8 * 9 + 3
 3 - 8 x 9 + 3 = ?
Answer = -66
Convert to absolute value
New Answer = 66

thank you brother

 

[Farzam]

Here is another suggestion :

Private Sub generate As String
    Dim digit() As String = Array As String("1", "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 result, discards As Int
    Do Until (result > 0)
        equation = digit(Rnd(0, 9)) & operator(Rnd(0, 3)) & digit(Rnd(0, 9)) & operator(Rnd(0, 3)) & digit(Rnd(0, 9))
        result = e.Eval(equation)
        If (result < 1) Then discards = discards + 1
    Loop
    Log("Equation = " & equation & " = " & result & ";  Discards = " & discards)
    Return equation
End Sub

. . . and some results . . .



Of course, we have not introduced division here; that would be much more complicated, assuming we are looking for integer results.

Thank you brother, your code was used

 

[Brian Dean]

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 . . .

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 . . .

Equation = 7 x 2 - 6 = 8
Equation = 6 + 3 - 4 = 5
Equation = 4 x 7 + 8 = 36
Equation = 5 + 9 - 2 = 12
Equation = 2 x 5 + 8 ÷ 2 = 14
Equation = 9 + 2 + 9 x 7 = 74
Equation = 5 + 5 + 3 x 7 = 31
Equation = 7 + 2 x 4 = 15
Equation = 6 x 7 + 3 = 45
Equation = 4 + 5 + 5 = 14

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.