Strvar

Strvar is an esolang by User:PythonshellDebugwindow based on string rewriting.

Syntax

Every non-blank line in a valid Strvar program is either a variable definition or a lone string literal. Variable definitions look like this:

myVar = "myString";

Lone string literals look like this:

"myString";

A lone string literal on a line will be output followed by a newline. Valid escape codes in strings are \r \n \" \t \xhh. Variables can be reassigned a new (or the same) value. Variable names must match the regex [^\s"#;=]+. Spaces outside of strings are ignored, including in variable names, so at assignment, "my var" and "myvar" are the same variable, both changed to "myvar". Comments are denoted by a #, are ignored, and last until end-of-line.

String rewriting

Each time a string literal is evaluated, it is checked to see if it contains any variable names. If it does, then the following actions take place:

1. The first occurrence of a variable name in the string is replaced with the variable's value.
2. If there is still a variable name in the string, then repeat the process.

This will result in an infinite loop if a variable used in a string is set to its own name, as it will always contain the name (and value) of the variable.

Examples

Hello, World!

"Hello, World!";

Showing off more features:

h = "Hello,";
w = "World!";
"h w";

The string ends up with infinitely many "orld!"s on the end, and never gets printed out because the program goes into an infinite loop:

h = "Hello,";
w = "world!";
"h w";

Truth-machine

Change "0" to "1" for input 1. Loops forever for 1 = "1";, prints 0 for 1 = "0";.

1 = "0";
"1";

Interpreter test cases

This code:

a = "b";
b = "c";
"a";

should print "b", and this code:

b = "x";
a = "b";
b = "y";
"a";

should print "x".

Counter

This program prints the string “1 2 3”:

one = "1";
two = "one 2";
three = "two 3";
"three";

Resources

• An unfinished interpreter written in NodeJS
• Common Lisp implementation of the Strvar programming language.