DSSL2: Data Structures Student Language🔗ℹ

DSSL2 is a programming language for data structures students. It’s designed to be simple, providing the essential building blocks one needs to implement a variety of data structures, but leaving out the finished products for students to build themselves.

DSSL2 is a close cousin of Python, with a similar indentation-sensitive syntax and similar function and keyword names when possible. For example, this is a DSSL2 program:

#lang dssl2

struct node:

let key

let left

let right

def insert(t, k):

if t is None:

t = node(k, None, None)

elif k < t.key:

t.left = insert(t.left, k)

elif k > t.key:

t.right = insert(t.right, k)

return t

let t1 = insert(None, 1)

let t2 = insert(t1, 2)

let t3 = insert(t2, 3)

Like Python, DSSL2 uses alignment and indentation to delimit blocks. In particular, compound statements such as def or if-elif-else take ⟨block⟩s for each condition, where a ⟨block⟩ can be either one simple statement followed by a newline, or a sequence of statements on subsequent lines that are all indented by four additional spaces. Extraneous indentation is an error.

DSSL2 deviates from Python in a number of places for pedagogical reasons. Some of these deviations include (non-exhaustive list):

• the base data structures: replaced instead by basic arrays and structs

• the object system: which emphasizes encapsulation and interfaces

• variable declarations: to avoid Python’s scope gotchas.

Nonetheless, students familiar with Python should feel at home in DSSL2. And students learning DSSL2 should have a head start when learning Python.