PNLC

A toy functional language

Overview

PNLC is λ‑calculus in prefix notation plus normal-order semantics plus continuation-based I/O plus a small prelude. Arguably, the prelude is the language, because without it you’re left with little more than a λ‑calculus interpreter.

The grammar for the language is specified in grammar.bnf. Roughly speaking,

<term> ::= "." <term> <term> ; application
         | "\\" <var> <term> ; abstraction
         | <var>             ; variable

During execution, the top-level term is expected to β‑reduce to one of the following forms, at which point the corresponding effect is performed. The prelude provides monadic wrappers for use in user programs.

Form	Effect
$exit	Terminate the program normally.
$err …	Ignore any arguments, crash the program.
.$get cont	Read one bit from stdin, invoke cont with it. \s \n n means EOF, \s \n .s \t \f t means one, \s \n .s \t \f f means zero.
..$put bit cont	Write bit to stdout, invoke cont without arguments. A bit of \t \f t means one, \t \f f means zero.
..$eput bit cont	Write bit to stderr, invoke cont without arguments. A bit of \t \f t means one, \t \f f means zero.
..$dump term cont	Reduce term to weak head normal form, dump it to stderr, invoke cont without arguments.

Usage

First compile the interpreter:

make bin/pnlc

Then run some example programs:

bin/pnlc examples/no-op\ naked.pnlc
bin/pnlc examples/hello\ world\ naked.pnlc
bin/pnlc examples/bit-cat\ naked.pnlc
bin/pnlc prelude.pnlc examples/no-op.pnlc
bin/pnlc prelude.pnlc examples/hello\ world.pnlc
bin/pnlc prelude.pnlc examples/bit-cat.pnlc
bin/pnlc prelude.pnlc examples/chr-cat.pnlc
bin/pnlc prelude.pnlc examples/greeting.pnlc
bin/pnlc prelude.pnlc examples/truth-machine.pnlc
bin/pnlc prelude.pnlc examples/reverse.pnlc
bin/pnlc prelude.pnlc examples/rot13.pnlc
bin/pnlc prelude.pnlc examples/quine.pnlc
bin/pnlc io\ hook.pnlc prelude.pnlc examples/hello\ world.pnlc
bin/pnlc io\ hook.pnlc prelude.pnlc examples/bit-cat.pnlc

# PNLC self-interpreter demos
bin/pnlc prelude.pnlc examples/pnlc.pnlc
cat examples/no-op\ naked.pnlc | bin/pnlc prelude.pnlc examples/pnlc.pnlc
cat examples/hello\ world\ naked.pnlc | bin/pnlc prelude.pnlc examples/pnlc.pnlc
cat examples/bit-cat\ naked.pnlc nul - | bin/pnlc prelude.pnlc examples/pnlc.pnlc
cat io\ hook.pnlc examples/hello\ world\ naked.pnlc | bin/pnlc prelude.pnlc examples/pnlc.pnlc
cat io\ hook.pnlc examples/bit-cat\ naked.pnlc nul - | bin/pnlc prelude.pnlc examples/pnlc.pnlc

# Brainfuck interpreter demos
bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/pnlc.bf | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/bell.bf | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/ascii.bf | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/cat.bf bang - | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/reverse.bf bang - | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/beaver.bf | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/clear.bf | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/head.bf bang - | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/strip.bf bang - | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/truth-machine.bf bang - | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/bin2text.bf bang - | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/text2bf.bf bang - | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/fib.bf | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/squares.bf | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/thuemorse.bf | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/sierpinski.bf | bin/pnlc prelude.pnlc examples/brainfuck.pnlc
cat examples/bf/siercarpet.bf | bin/pnlc prelude.pnlc examples/brainfuck.pnlc