* Assertions.

* Logical operators (!, &&, ||, ->).
This commit is contained in:
Eelco Dolstra 2003-11-05 16:27:40 +00:00
parent e17e95a828
commit fa18f1f184
6 changed files with 77 additions and 16 deletions

View file

@ -13,11 +13,6 @@ EvalState::EvalState()
}
Expr getAttr(EvalState & state, Expr e, const string & name)
{
}
/* Substitute an argument set into the body of a function. */
static Expr substArgs(Expr body, ATermList formals, Expr arg)
{
@ -142,7 +137,8 @@ Expr evalExpr2(EvalState & state, Expr e)
ATmatch(e, "Bool(<term>)", &e1) ||
ATmatch(e, "Function([<list>], <term>)", &e1, &e2) ||
ATmatch(e, "Attrs([<list>])", &e1) ||
ATmatch(e, "List([<list>])", &e1))
ATmatch(e, "List([<list>])", &e1) ||
ATmatch(e, "Null", &e1))
return e;
/* Any encountered variables must be undeclared or primops. */
@ -163,6 +159,8 @@ Expr evalExpr2(EvalState & state, Expr e)
if (primop == "derivation") return primDerivation(state, e2);
if (primop == "toString") return primToString(state, e2);
if (primop == "baseNameOf") return primBaseNameOf(state, e2);
if (primop == "null") return primNull(state, e2);
if (primop == "isNull") return primIsNull(state, e2);
else throw badTerm("undefined variable/primop", e1);
}
@ -200,13 +198,36 @@ Expr evalExpr2(EvalState & state, Expr e)
return evalExpr(state, e3);
}
/* Equality. Just strings for now. */
if (ATmatch(e, "OpEq(<term>, <term>)", &e1, &e2)) {
string s1 = evalString(state, e1);
string s2 = evalString(state, e2);
return s1 == s2 ? ATmake("Bool(True)") : ATmake("Bool(False)");
/* Assertions. */
if (ATmatch(e, "Assert(<term>, <term>)", &e1, &e2)) {
if (!evalBool(state, e1)) throw badTerm("guard failed", e);
return evalExpr(state, e2);
}
/* Generic equality. */
if (ATmatch(e, "OpEq(<term>, <term>)", &e1, &e2))
return makeBool(evalExpr(state, e1) == evalExpr(state, e2));
/* Generic inequality. */
if (ATmatch(e, "OpNEq(<term>, <term>)", &e1, &e2))
return makeBool(evalExpr(state, e1) != evalExpr(state, e2));
/* Negation. */
if (ATmatch(e, "OpNot(<term>)", &e1))
return makeBool(!evalBool(state, e1));
/* Implication. */
if (ATmatch(e, "OpImpl(<term>, <term>)", &e1, &e2))
return makeBool(!evalBool(state, e1) || evalBool(state, e2));
/* Conjunction (logical AND). */
if (ATmatch(e, "OpAnd(<term>, <term>)", &e1, &e2))
return makeBool(evalBool(state, e1) && evalBool(state, e2));
/* Disjunction (logical OR). */
if (ATmatch(e, "OpOr(<term>, <term>)", &e1, &e2))
return makeBool(evalBool(state, e1) || evalBool(state, e2));
/* Barf. */
throw badTerm("invalid expression", e);
}

View file

@ -222,3 +222,9 @@ Expr substitute(const ATermMap & subs, Expr e)
return e;
}
Expr makeBool(bool b)
{
return b ? ATmake("Bool(True)") : ATmake("Bool(False)");
}

View file

@ -45,7 +45,6 @@ public:
ATerm string2ATerm(const string & s);
string aterm2String(ATerm t);
/* Generic bottomup traversal over ATerms. The traversal first
recursively descends into subterms, and then applies the given term
function to the resulting term. */
@ -69,5 +68,8 @@ Expr makeAttrs(const ATermMap & attrs);
/* Perform a set of substitutions on an expression. */
Expr substitute(const ATermMap & subs, Expr e);
/* Create an expression representing a boolean. */
Expr makeBool(bool b);
#endif /* !__FIXEXPR_H */

View file

@ -38,6 +38,8 @@ exports
Id -> Formal {cons("NoDefFormal")}
Id "?" Expr -> Formal {cons("DefFormal")}
"assert" Expr ";" Expr -> Expr {cons("Assert"), right}
"rec" "{" Binds "}" -> Expr {cons("Rec")}
"let" "{" Binds "}" -> Expr {cons("LetRec")}
"{" Binds "}" -> Expr {cons("Attrs")}
@ -55,7 +57,13 @@ exports
"if" Expr "then" Expr "else" Expr -> Expr {cons("If")}
Expr "==" Expr -> Expr {cons("OpEq")}
Expr "==" Expr -> Expr {cons("OpEq"), non-assoc}
Expr "!=" Expr -> Expr {cons("OpNEq"), non-assoc}
"!" Expr -> Expr {cons("OpNot")}
Expr "&&" Expr -> Expr {cons("OpAnd"), right}
Expr "||" Expr -> Expr {cons("OpOr"), right}
Expr "->" Expr -> Expr {cons("OpImpl"), right}
Bool -> Expr {cons("Bool")}
@ -64,6 +72,13 @@ exports
Expr "." Id -> Expr
> Expr ExprList -> ExprList
> Expr Expr -> Expr
> "!" Expr -> Expr
> Expr "==" Expr -> Expr
> Expr "!=" Expr -> Expr
> Expr "&&" Expr -> Expr
> Expr "||" Expr -> Expr
> Expr "->" Expr -> Expr
> "assert" Expr ";" Expr -> Expr
> "{" {Formal ","}* "}" ":" Expr -> Expr
@ -78,6 +93,7 @@ exports
"rec" -> Id {reject}
"true" -> Id {reject}
"false" -> Id {reject}
"assert" -> Id {reject}
[0-9]+ -> Int

View file

@ -225,3 +225,16 @@ Expr primToString(EvalState & state, Expr arg)
return ATmake("Str(<str>)", s);
else throw badTerm("cannot coerce to string", arg);
}
Expr primNull(EvalState & state, Expr arg)
{
return ATmake("Null");
}
Expr primIsNull(EvalState & state, Expr arg)
{
arg = evalExpr(state, arg);
return makeBool(ATmatch(arg, "Null"));
}

View file

@ -8,7 +8,6 @@
argument. */
Expr primImport(EvalState & state, Expr arg);
/* Construct (as a unobservable) side effect) a Nix derivation
expression that performs the derivation described by the argument
set. Returns the original set extended with the following
@ -18,14 +17,18 @@ Expr primImport(EvalState & state, Expr arg);
derivation. */
Expr primDerivation(EvalState & state, Expr args);
/* Return the base name of the given string, i.e., everything
following the last slash. */
Expr primBaseNameOf(EvalState & state, Expr arg);
/* Convert the argument (which can be a path or a uri) to a string. */
Expr primToString(EvalState & state, Expr arg);
/* Return the null value. */
Expr primNull(EvalState & state, Expr arg);
/* Determine whether the argument is the null value. */
Expr primIsNull(EvalState & state, Expr arg);
#endif /* !__PRIMOPS_H */