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#ifndef __NIXEXPR_H
#define __NIXEXPR_H
#include <map>
#include <aterm2.h>
#include "aterm-map.hh"
#include "util.hh"
MakeError(EvalError, Error)
MakeError(AssertionError, EvalError)
MakeError(TypeError, EvalError)
/* Nix expressions are represented as ATerms. The maximal sharing
property of the ATerm library allows us to implement caching of
normals forms efficiently. */
typedef ATerm Expr;
typedef ATerm Pos;
/* A STL vector of ATerms. Should be used with great care since it's
stored on the heap, and the elements are therefore not roots to the
ATerm garbage collector. */
typedef vector<ATerm> ATermVector;
/* A substitution is a linked list of ATermMaps that map names to
identifiers. We use a list of ATermMaps rather than a single to
make it easy to grow or shrink a substitution when entering a
scope. */
struct Substitution
{
ATermMap * map;
const Substitution * prev;
Substitution(const Substitution * prev, ATermMap * map)
{
this->prev = prev;
this->map = map;
}
Expr lookup(Expr name) const
{
Expr x;
for (const Substitution * s(this); s; s = s->prev)
if (x = s->map->get(name)) return x;
return 0;
}
};
/* Show a position. */
string showPos(ATerm pos);
/* Generic bottomup traversal over ATerms. The traversal first
recursively descends into subterms, and then applies the given term
function to the resulting term. */
struct TermFun
{
virtual ATerm operator () (ATerm e) = 0;
};
ATerm bottomupRewrite(TermFun & f, ATerm e);
/* Query all attributes in an attribute set expression. The
expression must be in normal form. */
void queryAllAttrs(Expr e, ATermMap & attrs, bool withPos = false);
/* Query a specific attribute from an attribute set expression. The
expression must be in normal form. */
Expr queryAttr(Expr e, const string & name);
Expr queryAttr(Expr e, const string & name, ATerm & pos);
/* Create an attribute set expression from an Attrs value. */
Expr makeAttrs(const ATermMap & attrs);
/* Perform a set of substitutions on an expression. */
Expr substitute(const Substitution & subs, Expr e);
/* Check whether all variables are defined in the given expression.
Throw an exception if this isn't the case. */
void checkVarDefs(const ATermMap & def, Expr e);
/* Create an expression representing a boolean. */
Expr makeBool(bool b);
string showType(Expr e);
#endif /* !__NIXEXPR_H */
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