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ScalaCheck custom generator examples

Table of Contents1 - Custom generators2 - Built-in ScalaCheck generators3 - How to use ScalaCheck generators4 - More ScalaCheck generators

Writing custom generators for ScalaCheck can be one of the more difficult and/or time-consuming parts of using it. As a result I thought I’d start putting together a list of generators that I have written or seen elsewhere. Unfortunately I can’t credit all the ones I’ve seen in other places because I google’d and copied them many moons ago, but I’ll give credit/attribution to all the ones I can.

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Custom generators

This is a combination of generators I wrote, and some that I copied from other places and may have modified a little:

Scala: Generating a sequence/list of all ASCII printable characters

I ran into a couple of interesting things today when trying to generate random alphanumeric strings in Scala, which can be summarized like this. I won’t get into the “random” stuff I was working on, but here are a couple of examples of how to generate lists of alphanumeric/ASCII characters in Scala:

scala> val chars = ('a' to 'Z').toList
chars: List[Char] = List()

scala> val chars = ('A' to 'z').toList
chars: List[Char] = 
List(A, B, C, D, E, F, G, H, I, J, K, L, 
     M, N, O, P, Q, R, S, T, U, V, W, X, 
     Y, Z, [, \, ], ^, _, `, a, b, c, d, 
     e, f, g, h, i, j, k, l, m, n, o, p, 
     q, r, s, t, u, v, w, x, y, z)

scala> val chars = (' ' to 'z').toList
chars: List[Char] = 
List( , !, ", #, $, %, &, ', (, ), *, +, 
     ,, -, ., /, 0, 1, 2, 3, 4, 5, 6, 7, 
     8, 9, :, ;, <, =, >, ?, @, A, B, C, 
     D, E, F, G, H, I, J, K, L, M, N, O, 
     P, Q, R, S, T, U, V, W, X, Y, Z, [, 
     \, ], ^, _, `, a, b, c, d, e, f, g, 
     h, i, j, k, l, m, n, o, p, q, r, s, 
     t, u, v, w, x, y, z)

How to remove extended ASCII characters from Unix files with the 'tr' command

When working with text files on a Unix/Linux system, you'll occasionally run into a situation where a file will contain extended ASCII characters. These extended characters will generally appear to begin with ^ or [characters in your text files. For instance, the vi/vim editor will show ^M characters in DOS text files when they are transferred to Unix systems, such as when using the ftp command in binary transfer mode. Oftentimes, you'll want to easily delete these characters from your files.

ASCII drawing programs

Every time I go back to writing GUI programs, I find that I want to document my UI layout code, especially when I use something like a JGoodies layout in a Java/Swing application. I just took a look around and found some ASCII drawing programs, which may help me create the documentation I’m looking for, i.e., an ASCII drawing I can put in my Java/Scala comments, above my UI layout code. I created this particular drawing with asciiflow.com.

A Ruby script to remove binary (garbage) characters from a text file

Problem: You have a file that should be a plain text file, but for some reason it has a bunch of non-printable binary characters (also known as garbage characters) in it, and you'd like a Ruby script that can create a clean version of the file.

Solution: I've demonstrated how to do this in another blog post by using the Unix tr command, but in case you'd like a Ruby script to clean up a file like this, I thought I'd write up a quick program and share it here.

Ruby - How to convert ASCII decimal (byte) values to characters

Problem: You have a byte value, or a string of byte values, and you want to use a Ruby script to convert each byte to its equivalent ASCII character.

Solution

I just ran into this problem while working on a script to remove binary/garbage characters from a Unix text file. In short, the file had a bunch of binary "garbage" characters in it, and I wanted a clean version of the file that contained only printable ASCII characters in it.

Ruby - How to convert characters to ASCII decimal (byte) values

Problem: You have a character, or a string of characters, and you want to use a Ruby script to convert each character to its ASCII decimal (byte) value.

Solution

I just ran into this problem while working on a script to remove binary/garbage characters from a Unix text file. In short, all you have to do to convert a character in Ruby to its equivalent decimal ASCII code is use the ? operator in front of it, like this: