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ksplang - the best programming language

ksplang is a stack-based programming language with 33 instructions, independently designed by 33 people. Proven best by the logic of a Czech children's story.

About the language

The famous Czech children's story Jak si pejsek s kočičkou dělali k svátku dort (English translation) by Josef Čapek teaches that you can bake the best cake by adding many good things into it. Yes, that is definitely the correct interpretation. We have decided to prove this experimentally, with a programming language.

We have done this within KSP, a Czech programming competition for high-school students. Within the first series of tasks of the 36th year, we have asked each competitor for a single original instruction for a stack-based language. Within the second and third series we have assigned tasks to solve in ksplang.

The basics

We have one stack of limited size (configurable) of 64-bit signed values (-2^63 to 2^63-1). The initial stack is the input, the resulting stack is the output. Overflows are generally an error, so is indexing out of bounds. The list of instructions is indexed from zero. Instructions have ids (0 to 32). Programs are sequences of case insensitive instructions, separated by whitespace. No comments are allowed. The program ends when the program naturally reaches past the end or the start when executing backwards.

Tasks

These tasks can be a good starting point for learning the language. In all tasks, the input stack is non-empty.

  • 36-2-4, task 1: Add 0 to the stack
  • 36-2-4, task 2: Turn x into -x (except for -2^63)
  • 36-2-4, task 3: Duplicate a number
  • 36-3-4, task 1: Turn positive k into a sequence k k-1 ... 0
  • 36-3-4, task 2: Sort the stack (given its length)
  • 36-3-4, task 3: Calculate the stack length

Overview of instructions

You can check out the original Czech instruction list here, but we also provide a translation of all the instructions here.

Generally, we talk about the stack growing right or upwards.

Stack manipulation

ID Zápis Popis
0 praise Adds "Mám rád KSP" N times (Czech for "I like KSP").
1 pop Removes the top value.
2 pop2 Removes the second value from the top.
3 max Removes the smaller of the top two values.
4 L-swap Swaps the first and last value on the stack.
5 lroll Rolls the top N values on the stack K positions to the right.
6 -ff If the top of the stack is 2, then 4, do nothing; otherwise empty the stack and fill it with -2^63.
7 swap Pop an index n, then swap new top value with n-th value from the bottom (zero-indexed).
8 kPi Gets decimal digits of π (see full description for details).

Arithmetic

ID Zápis Popis
9 ++ Increments the top number by 1.
10 u Universal arithmetic; first pops operation id, then does addition/absolute difference/multiplication/division or remainder/factorial/sign.
11 REM Truncated division modulo (like a % b in C).
12 % Euclidean modulo (like a % abs(b) in Python).
13 tetr Tetration.
14 ^^ Tetration (reverse parameter order compared to tetr).
15 m Median of top k numbers, k is top value on the stack (not removed).
16 CS Digit sum of top number (not removed).
17 lensum Sum "decimal lengths" of top two numbers on the stack.
18 bitshift Left bitshift.
19 And Bitwise AND of top two numbers.
20 sum Sum the entire stack.
21 gcd GCD of two numbers.
22 d GCD of n numbers.
23 qeq Finds integer solutions of quadratic equations.
24 funkcia Factorizes 2 numbers and multiplies the factorization except for common primes, modulo 1000000007.
25 bulkxor Pops N and then applies XOR to N pairs of values interpreted as x > 0 and creates N zeros/ones.

Control flow

IP is the current instruction pointer.

ID Zápis Popis
26 BRZ Sets IP to second top value if the top is zero (conditional absolute jump).
27 call Adds IP+1 to the stack and sets top of the stack as IP (absolute jump with return IP).
28 GOTO Sets IP to top value (absolute jump).
29 j Adds top value + 1 to IP (relative jump).
30 rev Jumps forward, rotates the stack and executes code backwards until itself (see full description for details)

Other

ID Zápis Popis
31 SPANEK During task evaluation, gives double the points and goes to sleep... (results in a timeout error)
32 deez Reads n values, translates them to instructions by their ids, evaluates the subprogram and appends the resulting stack as instructions to the end of the program.