9279174dde
in attribute set pattern matches. This allows defining a function
that takes *at least* the listed attributes, while ignoring
additional attributes. For instance,
{stdenv, fetchurl, fuse, ...}:
stdenv.mkDerivation {
...
};
defines a function that requires an attribute set that contains the
specified attributes but ignores others. The main advantage is that
we can then write in all-packages.nix
aefs = import ../bla/aefs pkgs;
instead of
aefs = import ../bla/aefs {
inherit stdenv fetchurl fuse;
};
This saves a lot of typing (not to mention not having to update
all-packages.nix with purely mechanical changes). It saves as much
typing as the "args: with args;" style, but has the advantage that
the function arguments are properly declared (not implicit in what
the body of the "with" uses).
122 lines
3 KiB
C++
122 lines
3 KiB
C++
#ifndef __NIXEXPR_H
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#define __NIXEXPR_H
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#include <map>
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#include "aterm-map.hh"
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#include "types.hh"
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namespace nix {
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MakeError(EvalError, Error)
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MakeError(AssertionError, EvalError)
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MakeError(ThrownError, AssertionError)
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MakeError(Abort, EvalError)
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MakeError(TypeError, EvalError)
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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 DefaultValue;
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typedef ATerm Pos;
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typedef ATerm Pattern;
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typedef ATerm ATermBool;
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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 ~TermFun() { }
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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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/* Canonicalise a Nix expression by sorting attributes and removing
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location information. */
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Expr canonicaliseExpr(Expr e);
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/* Create an expression representing a boolean. */
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Expr makeBool(bool b);
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/* Manipulation of Str() nodes. Note: matchStr() does not clear
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context! */
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bool matchStr(Expr e, string & s, PathSet & context);
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Expr makeStr(const string & s, const PathSet & context = PathSet());
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/* Showing types, values. */
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string showType(Expr e);
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string showValue(Expr e);
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}
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#endif /* !__NIXEXPR_H */
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