VIPER is a visual interpreter of a slightly adjusted version of Pascal, created as part of the OSI (Open Studies in Computer Science) platform wazniak.mimuw.edu.pl.

Authors

• Piotr Chrzastowski-Wachtel
• Anna Niewiarowska
• Michal Adamaszek

Downloads:

• Complete package (English): a short manual, syntax, sample programs and the stand-alone application all in English vip-en.zip
• Complete package (Polish): a manual, syntax, sample programs and the stand-alone application all in Polish vip-pl.zip

Run as Java applet:

• English
• Polish

Screenshots

Demos
Almost all the demonstration animations come from the OSI website. Their authors are Piotr Chrzastowski-Wachtel, Jacek Chrzaszcz and Daria Walukiewicz-Chrzaszcz.

• The longest common subsequence
• Inserting numbers into a BST
• The three-colour flag I
• The three-colour flag II
• The longest constant subsequence I
• The longest constant subsequence II
• The longest constant subsequence of a sorted array
• The maximal subsequence sum I
• The maximal subsequence sum II
• The maximal subsequence sum III
• The maximal subsequence sum IV
• The maximal subsequence sum V
• The intersection of sets
• The union of sets I
• The union of sets II
• Is one array a sub-sequence of another
• Reversing an array I
• Reversing an array II
• The cyclic shift of an array I
• The cyclic shift of an array II
• The lexicographically next permutation
• An array segment with given sum I
• An array segment with given sum II
• Voting I
• Voting II
• Binary search for the first ocurrence of x
• Binary search for the last ocurrence of x
• Binary search for an index i with A[i]=i
• The maximum of an increasing-then-decreasing sequence
• Computing the ceil of sqrt(x) I
• Computing the ceil of sqrt(x) II
• Computing the floor of sqrt(x)
• Binary powering
• The longest non-decreasing subsequence
• Partitions of integers
• Reversing a list
• Merging two sorted lists
• Removing the contents of a list from another list
• The three-colouring of a list
• Counting the leaves of a tree
• Mirror symmetry of a tree
• The isomorphism of binary trees
• Linking the leaves in a list

Quick intro

• EN: The left window is for the source code, under it are the output and error consoles. The right frame displays the memory, gray buttons turn the visibility of variables on and off. First you need to compile your code (press the compile button). You will be prompted for the input data (if any). After compilation it is not possible to edit the code. You may now start the program or step through it. The program can be stopped at any time and speed can be adjusted. When the program is over press the end button to return to edit mode.
• PL: W oknie po lewej piszemy tekst programu, pod spodem na szarym tle jest konsola na outputy, jeszcze nizej konsola na komunikaty kompilatora. Na zoltym tle sa zmienne, szarymi przyciskami na gorze mozna wlaczac/wylaczac widocznosc. Najpierw kompilujemy program (kompiluj) co wczytuje tez dane wejsciowe. Jesli kompilcja byla OK, to od tego momentu edycja jest zablokowana. Potem mozna uruchamiac (krok po kroku lub startem - zatrzymanie w dowolnej chwili przez stop). Jak nam sie znudzi klikamy Koniec i wracamy do trybu edycji kodu.

Papers

• VIPER, a Student-friendly Interpreter of Pascal; Michal Adamaszek, Piotr Chrzastowski-Wachtel, Anna Niewiarowska, Proc. ISSEP'2008, LNCS 5090, 192-203

Acknowlegments.

• We thank the following people who submitted bug-reports, suggestions, or otherwise contributed to VIPER: Maksymilian Osowski.

Changelog

• 1.11.2007
  • Lower- and upper-case in keywords
• 1.11
  • 2D arrays
  • More i18n: configurable special names of fields in trees and lists
  • Checked that it compiles in Java 1.5
• 18.10
  • The memory display frame is scalable (more can fit in)
  • Distinguishing various kinds of compile errors
  • The ability to read a variable's value from the previous program run
  • Comparisons of booleans (somehow we missed that before)
  • Arrays of reals, bools and pointers are displayed
• 7.10
  • Trees
  • i18n
  • Highlighting the code entry point of a stack frame
  • A lot of bugfixes
  • Unified the applet with the stand-alone program
• 28.08
  • Speed adjustment slider
  • New array initialization schemes
  • Bidirectional lists
• 24.08
  • One-directional lists
  • Breakpoints, step into/over
  • Detecting unreferenced data (garbage collection)
  • Reading initial values without the pop-up dialog box
  • Pointer highlighting by mouse-click
  • Functions sqrt(x), zamien(a,b), max(...), min(...)
  • Arithmetic errors control
  • Less strict syntax (semicolons)
• 04.08
  • Records
  • Pointers and their comparisons
  • Functions, procedures, stack. Parameters by value and by variable.
• 17.07.2006
  • Arrays of int, real, bool
  • Array indicies with dynamic updating
  • Initialization of primitives and arrays
  • Highlighting in the source code
  • Variable visibility control
  • Basic instructions of Pascal work
  • Step by step execution and start/stop buttons
  • Basic syntax error control, type-checking
  • Array range and uninitialized variable reads checked