Task: Balanced ternary
Go: package main

import (
    "fmt"
    "strings"
)




type bt []int8







func btString(s string) (*bt, bool) {
    s = strings.TrimLeft(s, "0")
    b := make(bt, len(s))
    for i, last := 0, len(s)-1; i < len(s); i++ {
        switch s[i] {
        case '-':
            b[last-i] = -1
        case '0':
            b[last-i] = 0
        case '+':
            b[last-i] = 1
        default:
            return nil, false
        }
    }
    return &b, true
}



func (b bt) String() string {
    if len(b) == 0 {
        return "0"
    }
    last := len(b) - 1
    r := make([]byte, len(b))
    for i, d := range b {
        r[last-i] = "-0+"[d+1]
    }
    return string(r)
}





func btInt(i int) *bt {
    if i == 0 {
        return new(bt)
    }
    var b bt
    var btDigit func(int)
    btDigit = func(digit int) {
        m := int8(i % 3)
        i /= 3
        switch m {
        case 2:
            m = -1
            i++
        case -2:
            m = 1
            i--
        }
        if i == 0 {
            b = make(bt, digit+1)
        } else {
            btDigit(digit + 1)
        }
        b[digit] = m
    }
    btDigit(0)
    return &b
}





func (b bt) Int() (r int, ok bool) {
    pt := 1
    for _, d := range b {
        dp := int(d) * pt
        neg := r < 0
        r += dp
        if neg {
            if r > dp {
                return 0, false
            }
        } else {
            if r < dp {
                return 0, false
            }
        }
        pt *= 3
    }
    return r, true
}


    
func (z *bt) Neg(b *bt) *bt {
    if z != b {
        if cap(*z) < len(*b) {
            *z = make(bt, len(*b))
        } else {
            *z = (*z)[:len(*b)]
        } 
    }
    for i, d := range *b {
        (*z)[i] = -d
    }
    return z 
}

func (z *bt) Add(a, b *bt) *bt {
    if len(*a) < len(*b) {
        a, b = b, a
    }
    r := *z
    r = r[:cap(r)]
    var carry int8 
    for i, da := range *a {
        if i == len(r) {
            n := make(bt, len(*a)+4)
            copy(n, r)
            r = n
        }
        sum := da + carry
        if i < len(*b) {
            sum += (*b)[i]
        }
        carry = sum / 3
        sum %= 3
        switch {
        case sum > 1:
            sum -= 3
            carry++
        case sum < -1:
            sum += 3
            carry--
        } 
        r[i] = sum 
    }
    last := len(*a)
    if carry != 0 {
        if len(r) == last {
            n := make(bt, last+4)
            copy(n, r)
            r = n
        }
        r[last] = carry
        *z = r[:last+1]
        return z
    }
    for {
        if last == 0 {
            *z = nil
            break
        }
        last--
        if r[last] != 0 {
            *z = r[:last+1]
            break
        }
    }
    return z
}

func (z *bt) Mul(a, b *bt) *bt {
    if len(*a) < len(*b) {
        a, b = b, a
    }
    var na bt
    for _, d := range *b {
        if d == -1 {
            na.Neg(a)
            break
        }
    }
    r := make(bt, len(*a)+len(*b))
    for i := len(*b) - 1; i >= 0; i-- {
        switch (*b)[i] {
        case 1:
            p := r[i:]
            p.Add(&p, a)
        case -1:
            p := r[i:]
            p.Add(&p, &na)
        }
    }
    i := len(r)
    for i > 0 && r[i-1] == 0 {
        i--
    }
    *z = r[:i]
    return z
}

func main() {
    a, _ := btString("+-0++0+")
    b := btInt(-436)
    c, _ := btString("+-++-")
    show("a:", a) 
    show("b:", b)
    show("c:", c)
    show("a(b-c):", a.Mul(a, b.Add(b, c.Neg(c))))
}   

func show(label string, b *bt) {
    fmt.Printf("%7s %12v ", label, b)
    if i, ok := b.Int(); ok {
        fmt.Printf("%7d\n", i)
    } else {
        fmt.Println("int overflow")
    }
}

VB: Imports System.Text

Module Module1
    Sub Main()
        Dim a As New BalancedTernary("+-0++0+")
        Console.WriteLine("a: {0} = {1}", a, a.ToLong)
        Dim b As New BalancedTernary(-436)
        Console.WriteLine("b: {0} = {1}", b, b.ToLong)
        Dim c As New BalancedTernary("+-++-")
        Console.WriteLine("c: {0} = {1}", c, c.ToLong)
        Dim d = a * (b - c)
        Console.WriteLine("a * (b - c): {0} = {1}", d, d.ToLong)
    End Sub

    Class BalancedTernary
        Private Enum BalancedTernaryDigit
            MINUS = -1
            ZERO = 0
            PLUS = 1
        End Enum

        Private ReadOnly value() As BalancedTernaryDigit

        
        Public Sub New()
            ReDim value(-1)
        End Sub

        
        Public Sub New(str As String)
            ReDim value(str.Length - 1)
            For i = 1 To str.Length
                If str(i - 1) = "-" Then
                    value(i - 1) = BalancedTernaryDigit.MINUS
                ElseIf str(i - 1) = "0" Then
                    value(i - 1) = BalancedTernaryDigit.ZERO
                ElseIf str(i - 1) = "+" Then
                    value(i - 1) = BalancedTernaryDigit.PLUS
                Else
                    Throw New ArgumentException("Unknown Digit: " + str(i - 1))
                End If
            Next
            Array.Reverse(value)
        End Sub

        
        Public Sub New(l As Long)
            Dim value As New List(Of BalancedTernaryDigit)
            Dim sign = Math.Sign(l)
            l = Math.Abs(l)

            While l <> 0
                Dim remainder = CType(l Mod 3, Byte)
                If remainder = 0 OrElse remainder = 1 Then
                    value.Add(remainder)
                    l /= 3
                ElseIf remainder = 2 Then
                    value.Add(BalancedTernaryDigit.MINUS)
                    l = (l + 1) / 3
                End If
            End While

            Me.value = value.ToArray
            If sign < 0 Then
                Invert()
            End If
        End Sub

        
        Public Sub New(origin As BalancedTernary)
            ReDim value(origin.value.Length - 1)
            Array.Copy(origin.value, value, origin.value.Length)
        End Sub

        
        Private Sub New(value() As BalancedTernaryDigit)
            Dim endi = value.Length - 1
            While endi > 0 AndAlso value(endi) = BalancedTernaryDigit.ZERO
                endi -= 1
            End While
            ReDim Me.value(endi)
            Array.Copy(value, Me.value, endi + 1)
        End Sub

        
        Private Sub Invert()
            For i = 1 To value.Length
                value(i - 1) = CType(-CType(value(i - 1), Integer), BalancedTernaryDigit)
            Next
        End Sub

        
        Public Overrides Function ToString() As String
            Dim result As New StringBuilder
            Dim i = value.Length - 1
            While i >= 0
                If value(i) = BalancedTernaryDigit.MINUS Then
                    result.Append("-")
                ElseIf value(i) = BalancedTernaryDigit.ZERO Then
                    result.Append("0")
                ElseIf value(i) = BalancedTernaryDigit.PLUS Then
                    result.Append("+")
                End If

                i -= 1
            End While
            Return result.ToString
        End Function

        
        Public Function ToLong() As Long
            Dim result = 0L
            For i = 1 To value.Length
                result += value(i - 1) * Math.Pow(3.0, i - 1)
            Next
            Return result
        End Function

        
        Public Shared Operator -(origin As BalancedTernary) As BalancedTernary
            Dim result As New BalancedTernary(origin)
            result.Invert()
            Return result
        End Operator

        
        Private Shared carry = BalancedTernaryDigit.ZERO
        Private Shared Function Add(a As BalancedTernaryDigit, b As BalancedTernaryDigit) As BalancedTernaryDigit
            If a <> b Then
                carry = BalancedTernaryDigit.ZERO
                Return a + b
            Else
                carry = a
                Return -CType(b, Integer)
            End If
        End Function

        
        Public Shared Operator +(a As BalancedTernary, b As BalancedTernary) As BalancedTernary
            Dim maxLength = Math.Max(a.value.Length, b.value.Length)
            Dim resultValue(maxLength) As BalancedTernaryDigit
            For i = 1 To maxLength
                If i - 1 < a.value.Length Then
                    resultValue(i - 1) = Add(resultValue(i - 1), a.value(i - 1))
                    resultValue(i) = carry
                Else
                    carry = BalancedTernaryDigit.ZERO
                End If

                If i - 1 < b.value.Length Then
                    resultValue(i - 1) = Add(resultValue(i - 1), b.value(i - 1))
                    resultValue(i) = Add(resultValue(i), carry)
                End If
            Next
            Return New BalancedTernary(resultValue)
        End Operator

        
        Public Shared Operator -(a As BalancedTernary, b As BalancedTernary) As BalancedTernary
            Return a + (-b)
        End Operator

        
        Public Shared Operator *(a As BalancedTernary, b As BalancedTernary) As BalancedTernary
            Dim longValue = a.value
            Dim shortValue = b.value
            Dim result As New BalancedTernary

            If a.value.Length < b.value.Length Then
                longValue = b.value
                shortValue = a.value
            End If

            For i = 1 To shortValue.Length
                If shortValue(i - 1) <> BalancedTernaryDigit.ZERO Then
                    Dim temp(i + longValue.Length - 2) As BalancedTernaryDigit
                    For j = 1 To longValue.Length
                        temp(i + j - 2) = CType(shortValue(i - 1) * longValue(j - 1), BalancedTernaryDigit)
                    Next
                    result += New BalancedTernary(temp)
                End If
            Next

            Return result
        End Operator
    End Class

End Module