Quylthulg

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Quylthulg is an esoteric programming language designed by Chris Pressey in 2008. It is a non-recursive pure functional language with a single control mechanism called foreach. In fact, it does also have a goto statement, but it may only occur inside data structures. It also features a macro processor (which is also non-recursive and which is intertwined somewhat with the rest of the language.)

Syntax

The majority of Quylthulg binary operations are expressed in "panfix" notation: the symbol indicating the operation precedes, follows, and is placed in-between the operands, as in:

+1+2+

Variable names consist of (nearly) arbitrary text surrounded by $ symbols.

The syntax of the foreach construct is:

foreach loop-var=list with accumulator=initial-value be expression else be expression

The foreach construct can double as an "if" and a "let".

Example program

foreach $n$=:L:[1,2,3|goto$L$] with $a$=1 be +$a$+$n$+ else be abort

Computational class

Although the foreach mechanism can only traverse a list, cyclic lists can be created using gotos. Quylthulg should therefore be Turing-complete; for instance, it should be possible to express the state-transition diagram of a Turing machine as a cyclic list which is foreach'ed over, and the tape of the Turing machine as a pair of lists passed into the accumulator of the foreach. However, this has never been formally proved.

External resources