* String/path concatenation operator (`+').

This commit is contained in:
Eelco Dolstra 2004-10-26 17:01:35 +00:00
parent ee401afad8
commit 9fa07b376d
6 changed files with 43 additions and 5 deletions

5
NEWS
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@ -49,8 +49,13 @@ Major changes include the following:
* Nix expression language changes: * Nix expression language changes:
* New language construct: `with E1; E2' brings all attributes
defined in the attribute set E1 in scope in E2.
* Added a `map' function. * Added a `map' function.
* Various new operators (e.g., string concatenation).
* An Emacs mode for editing Nix expressions (with syntax highlighting * An Emacs mode for editing Nix expressions (with syntax highlighting
and indentation) has been added. and indentation) has been added.

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@ -338,6 +338,20 @@ Expr evalExpr2(EvalState & state, Expr e)
return makeBool(attrs.get(name) != 0); return makeBool(attrs.get(name) != 0);
} }
/* String or path concatenation. */
if (atMatch(m, e) >> "OpPlus" >> e1 >> e2) {
e1 = evalExpr(state, e1);
e2 = evalExpr(state, e2);
string s1, s2;
if (atMatch(m, e1) >> "Str" >> s1 &&
atMatch(m, e2) >> "Str" >> s2)
return makeString(s1 + s2);
else if (atMatch(m, e1) >> "Path" >> s1 &&
atMatch(m, e2) >> "Path" >> s2)
return makeString(canonPath(s1 + "/" + s2));
else throw Error("wrong argument types in `+' operator");
}
/* Barf. */ /* Barf. */
throw badTerm("invalid expression", e); throw badTerm("invalid expression", e);
} }

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@ -364,3 +364,15 @@ Expr makeBool(bool b)
{ {
return b ? ATmake("Bool(True)") : ATmake("Bool(False)"); return b ? ATmake("Bool(True)") : ATmake("Bool(False)");
} }
Expr makeString(const string & s)
{
return ATmake("Str(<str>)", s.c_str());
}
Expr makePath(const Path & path)
{
return ATmake("Path(<str>)", path.c_str());
}

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@ -92,5 +92,11 @@ void checkVarDefs(const ATermMap & def, Expr e);
/* Create an expression representing a boolean. */ /* Create an expression representing a boolean. */
Expr makeBool(bool b); Expr makeBool(bool b);
/* Create an expression representing a string. */
Expr makeString(const string & s);
/* Create an expression representing a path. */
Expr makePath(const Path & path);
#endif /* !__NIXEXPR_H */ #endif /* !__NIXEXPR_H */

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@ -53,6 +53,7 @@ ATerm makePos(YYLTYPE * loc, void * data)
%nonassoc EQ NEQ %nonassoc EQ NEQ
%right UPDATE %right UPDATE
%left NEG %left NEG
%left '+'
%nonassoc '?' %nonassoc '?'
%nonassoc '~' %nonassoc '~'
@ -90,6 +91,7 @@ expr_op
| expr_op UPDATE expr_op { $$ = ATmake("OpUpdate(<term>, <term>)", $1, $3); } | expr_op UPDATE expr_op { $$ = ATmake("OpUpdate(<term>, <term>)", $1, $3); }
| expr_op '~' expr_op { $$ = ATmake("SubPath(<term>, <term>)", $1, $3); } | expr_op '~' expr_op { $$ = ATmake("SubPath(<term>, <term>)", $1, $3); }
| expr_op '?' ID { $$ = ATmake("OpHasAttr(<term>, <term>)", $1, $3); } | expr_op '?' ID { $$ = ATmake("OpHasAttr(<term>, <term>)", $1, $3); }
| expr_op '+' expr_op { $$ = ATmake("OpPlus(<term>, <term>)", $1, $3); }
| expr_app | expr_app
; ;

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@ -273,8 +273,8 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
attrs.set("outPath", ATmake("(Path(<str>), NoPos)", outPath.c_str())); attrs.set("outPath", ATmake("(Path(<str>), NoPos)", outPath.c_str()));
attrs.set("drvPath", ATmake("(Path(<str>), NoPos)", drvPath.c_str())); attrs.set("drvPath", ATmake("(Path(<str>), NoPos)", drvPath.c_str()));
attrs.set("drvHash", ATmake("(Str(<str>), NoPos)", ((string) drvHash).c_str())); attrs.set("drvHash", ATmake("(<term>, NoPos)", makeString(drvHash)));
attrs.set("type", ATmake("(Str(\"derivation\"), NoPos)")); attrs.set("type", ATmake("(<term>, NoPos)", makeString("derivation")));
return makeAttrs(attrs); return makeAttrs(attrs);
} }
@ -284,8 +284,7 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
following the last slash. */ following the last slash. */
static Expr primBaseNameOf(EvalState & state, const ATermVector & args) static Expr primBaseNameOf(EvalState & state, const ATermVector & args)
{ {
string s = evalString(state, args[0]); return makeString(baseNameOf(evalString(state, args[0])));
return ATmake("Str(<str>)", baseNameOf(s).c_str());
} }
@ -298,7 +297,7 @@ static Expr primToString(EvalState & state, const ATermVector & args)
if (atMatch(m, arg) >> "Str" >> s || if (atMatch(m, arg) >> "Str" >> s ||
atMatch(m, arg) >> "Path" >> s || atMatch(m, arg) >> "Path" >> s ||
atMatch(m, arg) >> "Uri" >> s) atMatch(m, arg) >> "Uri" >> s)
return ATmake("Str(<str>)", s.c_str()); return makeString(s);
else throw Error("cannot coerce value to string"); else throw Error("cannot coerce value to string");
} }