# Code Smell 100 - GoTo

*GOTO was considered harmful 50 years ago*

> TL;DR: Don't ever use GoTo.

# Problems

- Readability

- Hard to follow code

# Solutions

1. Replace [GOTO](https://en.wikipedia.org/wiki/Goto) with structured code

2. Use exceptions

# Context

I started programming in Basic. 

GOTO was heavily abused there. 

I had to learn structured programming from scratch in Rehab mode.

# Sample Code

## Wrong

[Gist Url]: # (https://gist.github.com/mcsee/5d76fda8dfbe6f351e709baa00e0e61c)
```go
for x < 0 {
    if x > -1e-09 {
      goto small
    }
    z = z / x
    x = x + 1
  }
  for x < 2 {
    if x < 1e-09 {
      goto small
    }
    z = z / x
    x = x + 1
  }

  if x == 2 {
    return z
  }

  x = x - 2
  p = (((((x*_gamP[0]+_gamP[1])*x+_gamP[2])*x+_gamP[3])*x+_gamP[4])*x+_gamP[5])*x + _gamP[6]
  q = ((((((x*_gamQ[0]+_gamQ[1])*x+_gamQ[2])*x+_gamQ[3])*x+_gamQ[4])*x+_gamQ[5])*x+_gamQ[6])*x + _gamQ[7]
  return z * p / q

small:
  if x == 0 {
    return Inf(1)
  }
  return z / ((1 + Euler*x) * x)
}
```

## Right

[Gist Url]: # (https://gist.github.com/mcsee/da74b8e901f234b6bc400c9a6e0b7725)
```go
for x < 0 {
    if x > -1e-09 {
      return small(x, z)
    }
    z = z / x
    x = x + 1
  }
  for x < 2 {
    if x < 1e-09 {
      return small(x, z)
    }
    z = z / x
    x = x + 1
  }

  if x == 2 {
    return z
  }

  x = x - 2
  p = (((((x*_gamP[0]+_gamP[1])*x+_gamP[2])*x+_gamP[3])*x+_gamP[4])*x+_gamP[5])*x + _gamP[6]
  q = ((((((x*_gamQ[0]+_gamQ[1])*x+_gamQ[2])*x+_gamQ[3])*x+_gamQ[4])*x+_gamQ[5])*x+_gamQ[6])*x + _gamQ[7]
  return z * p / q

small(x, z){
  if x == 0 {
     return Inf(1)
   }
   return z / ((1 + Euler*x) * x)
 }
}
```

# Detection

[X] Automatic 

In languages supporting *GOTO*, our linters can warn us against its usage.

# Tags

- Readability

# Conclusion

We acknowledged GOTO problems a few decades ago.

The problem is still present in modern languages.

Most programmers luckily avoid GOTO sentence. Next goal will be to consider harmful [null usage](https://maximilianocontieri.com/null-the-billion-dollar-mistake).

![goto.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1635896927741/V-GUhRsHV.png)

*Courtesy [XKCD](https://xkcd.com/292/)*

# Relations

%[https://maximilianocontieri.com/code-smell-12-null]

# More Info

- [Goto Statement considered harmful](https://homepages.cwi.nl/~storm/teaching/reader/Dijkstra68.pdf)

- [Wikipedia](https://en.wikipedia.org/wiki/Goto)

# Credits

Photo by <a href="https://unsplash.com/@jens_johnsson">Jens Johnsson</a> on <a href="https://unsplash.com/s/photos/sign">Unsplash</a>  

* * *

It is practically impossible to teach good programming to students that have had a prior exposure to BASIC: as potential programmers they are mentally mutilated beyond hope of regeneration.

_Edsger Dijkstra_
 
%[https://maximilianocontieri.com/software-engineering-great-quotes]

* * *

This article is part of the CodeSmell Series.

%[https://maximilianocontieri.com/how-to-find-the-stinky-parts-of-your-code]