stack.hpp (cpp-lecture/lambda/stack.hpp)

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#ifndef STACK_HPP
#define STACK_HPP

#include <cassert>
#include "types.hpp"

/*
   All functions have exactly one parameter. Hence, the
   function call stack consists of one value per call.
   For lexical scoped variables, the parser computes
   the relative offset of a variable.

   Examples: (lambda x x)                        x has the offset 0
             (lambda x (lambda y x))             x has the offset 1
         (lambda x (lambda y (lambda x x)))  x has the offset 0
         (lambda x (lambda y (lambda z x)))  x has the offset 2

   Each function value (see value.hpp) consists of a
   pointer to a function object and a stack pointer
   that provides all variables required by the closure.

   The []-operator of Stack delivers the value with offset i for [i].
*/

namespace LambdaCalc {

   class Stack {
      public:
     StaStackPtrPtr nexValuePtrPtr value) :
        nenextext), valvaluelue), lnextexnextexlengt;len+1: 1) {
     }
  ValuePtrbsp; ValuePtr operator[](unsigned int index) const {
        asseindexdexlent; len);
        iindexan> (index == 0) retuvaluepan> value;
        returnnextp;(*nexindexdex-1];
     }
      private:
  ValuePtrbsp; ValuePtr value;
  StackPtrbsp; StackPtr next;
     unsigned int len;
   };

} // namespace LambdaCalc

#endif