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