Functionally Enhanced Abstract Syntax Tree (FEAST)
This is a hack, which, with the help of the macropy library, modifies the python AST at import time, with the idea of allowing for "nicer" functional programming in python.
Here, we show example code for computing the sum of prime numbers less than 100.
# "feast style"
maxfac = f[1 + (int& sqrt^ _)]
L.prime[k : k > 1 and 0 not in map/ (mod/k) ^ {2 >> maxfac/k}]
print sum ^ filter/ prime/ {100}
# is equivalent to the "normal" python syntax
maxfac = lambda k: 1 + int(sqrt(k))
prime = lambda k: k > 1 and 0 not in [k % x for x in range(2, maxfac(k))]
print sum((x for x in range(100) if prime(x)))
Features
- currying: all functions are automatically curried
- haskell style composition and application
&is composition
^is application (lower precedence than&)
/is application (higher precedence than&)
Examples:
f & g & h ^ x/ y/ z
is equivalent to the haskell syntax
f . g . h $ x y z
is equivalent to the python syntax
f(g(h(x(y)(z)))) - nicer syntax for defining functions
L.foo[x : stuff]
is equivalent to
foo = lambda x: stuff - nicer syntax for creating lambdas (macropy feature, NOT mine)
f[_+2]
is equivalent to
lambda x: x+2 - nicer ranges
{a >> b}
{N}
is equivalent to
range(a,b)
range(N)
Usage
The feast macro is defined in feast.py. Read the macropy documentation to understand how to use macros. See main.py for a working example. This was developed with python2.7 and macropy 1.0.3. At the moment, there are some minor incompatibilities with python3.x. The feast macro takes a single boolean argument, which, when set to False, will not modify &^/ inside quicklambdas. This is useful if you want to do normal arithmetic.