root/lang/unlambda/impl/in_python/unlambda_lambda.py @ 1767

""" unlambda interpreter

# test
>>> run("`.ai")
a
>>> run("``i.ai")
a
>>> run("`i`.ai")
a
>>> run("`d`.ai")
>>> run("``d`.aii")
a
>>> run("`.b`i`.ai")
ab
>>> run("`.b`d`.ai")
b
>>> run("``.b`d`.aii")
ba
>>> run("``.b`.a`ci.c")
ababc
>>> run("````skk.av")
a
"""
import sys

# Node
I = lambda:lambda c:c(lambda X,c:c(X))
Dot = lambda char:lambda c:c(
    lambda X,c:sys.stdout.write(char)or c(X))
Apply = lambda nX,nY:lambda c:\
    lambda:nX(lambda X:
        lambda:
            (X == D_)and(
                c(lambda Y,c:nY(lambda X:c(lambda X,c:X(Y,c))))
            )or(
                nY(lambda Y: lambda :X(Y, c))))
D = lambda:D_
D_ = lambda c:c(D_)
V0 = lambda X,c:c(V0)
V = lambda:lambda c:c(V0)
K = lambda:lambda c:c(lambda X,c:c(lambda Y,c:c(X)))
C = lambda:lambda c:c(lambda Y,c:lambda:Y(lambda F,c_:c(F),c))
S = lambda:lambda c:c(
        lambda X,c:c(
            lambda Y,c:c(
                lambda Z,c:lambda:(
                    Apply(
                        Apply(
                            lambda c:c(X),
                            lambda c:c(Z)),
                        Apply(
                            lambda c:c(Y),
                            lambda c:c(Z))))(c))))

def _parse(iter):
    return {
        "i": lambda: I(),
        "d": lambda: D(),
        "c": lambda: C(),
        "v": lambda: V(),
        "s": lambda: S(),
        "k": lambda: K(),
        "r": lambda: Dot("\n"),
        ".": lambda: Dot(iter.next()),
        "`": lambda: Apply(_parse(iter), _parse(iter)),
    }.get(iter.next(), lambda: _parse(iter))()

def parse(s):
    return _parse(list(s).__iter__())

# Main loop
def run(s):
    task = lambda:parse(s)(lambda f:lambda:None)
    while task:
        task = task()

# Test
def _test():
    import doctest
    reload(doctest)
    doctest.testmod()

def fib():
    "show Fibonacci numbers"
    run("""
    ```s``s``sii`ki
      `k.*``s``s`ks
     ``s`k`s`ks``s``s`ks``s`k`s`kr``s`k`sikk
      `k``s`ksk
      """)