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 tis 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.