js-lambda
DSL for, but not limited to, the lambda calculus.
USAGE
In Browser
node.js
var lambda = lambdaλ = lambda;
SYNOPSIS
42 === 42;42 === 42; // λ = lambda10 === 3628800; // _0 for recursion34 === 5; // multiple arguments, 34 === 5; // λ can be nested
// church numeralsvar cn2num = succ = zero = one = add = two = onemul = four = twopow = sixteen = four; === 16;
DESCRIPTION
This script exports lambda()
and its alias λ()
. As seen in the synopsis, it is a DSL compiler that returns a function.
the lambda notation
As seen in SYNOPSYS,
lambda(
arg0,arg1,...argn:expression)
Turns into:
function(
arg0, arg1, ...argn){return
expression }
nesting and recursion
As seen in SYNOPSYS, the lambda can be nested.
;
Turns into:
{return {return Math}}
As seen above, the function is named accordingly to De Bruijin index. _
n is the nth level function.
Use the name to implement self-recursion. The strict mode has deprived us of beloved arguments.callee
but with lambda.js, it is as short as _0
.
// function fact(n){ return n <= 1 ? n : n * fact(n-1) };
limitation
To use lexical functions, you have to "interpolate".
var succ = add = ; // λ("m:λ(n:m(succ)(n))") does not work
This is because lambda()
needs to eval()
to compile the function but lexicals are out of its scope.
memoization
By default, the compiled function is memoized. Suppose you have:
{ return Math}
And you use rms
over and over, the same function is used throughout the session. If that is not what you want, you can suppress it by passing truish value to the second argument:
var uncached = ;
And if you wish, you can inspect cached functions via lambda.memo
.