Lambda calculus parser & compiler.

lambda.pegjs

{
function compilejs(exp) {
 if(exp.length == 1) {
  return exp[0].replace(/[^a-zA-Z_$]/g, function(c) {
   return "_$" + c.charCodeAt(0).toString(16) + "$_"
  })
 } else if(exp.length == 2) {
  return compilejs(exp[0]) + "(" + compilejs(exp[1]) + ")"
 } else if(exp.length == 3) {
  return "(" + "function(" + compilejs(exp[1]) + ") {\n  "
  + "return " + compilejs(exp[2]).trim().split('\n').map(function(l) {
   return ' ' + l
  }).join('\n')
  + "\n})"
 }
}
function print(code) {
 return code + '\n====>\n' + (function() {
  try {
   return eval(code)
  } catch(e) {
   return 'Error: ' + e
  }
 })()
}
// ----
function lambda(a, r) {
 if(a.length == 1) {
  return ['lambda', a[0], r]
 } else {
  return ['lambda', a[0], lambda(a.slice(1), r)]
 }
}
}

prog
 =  f:exp space? a:exp { return print(compilejs([f, a])) }
 / e:exp { return print(compilejs(e)) }

exp
 = var
 / call
 / func
 / lparen e:exp rparen { return e }

var
 = n:(!lambda $[^\(\)λ\\\.])
 { return [n[1]] }

call
 = lparen f:exp space? a:exp rparen { return [f, a] }

func
 = lambda a:var+ dot r:exp
 {
  //alert(JSON.stringify(a))
  return lambda(a, r)
 }


lparen = "("
rparen = ")"
dot    = '.'
space  = ' '
lambda = ("lambda" / "λ" / "\\") { return "lambda" }

_ = [\r\n\t ]*