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Add a typeOf primop 

We already have some primops for determining the type of a value, such
as isString, but they're incomplete: for instance, there is no isPath.
Rather than adding more isBla functions, the generic typeOf function
returns a string representing the type of the argument (e.g. "int").
This commit is contained in:
Eelco Dolstra 2013-10-24 02:49:13 +02:00
parent 6da92d96ae
commit 05d02f798f
1 changed files with 28 additions and 3 deletions
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31
src/libexpr/primops.cc
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@ -92,6 +92,30 @@ static void prim_import(EvalState & state, Value * * args, Value & v)
}
/* Return a string representing the type of the expression. */
static void prim_typeOf(EvalState & state, Value * * args, Value & v)
{
state.forceValue(*args[0]);
string t;
switch (args[0]->type) {
case tInt: t = "int"; break;
case tBool: t = "bool"; break;
case tString: t = "string"; break;
case tPath: t = "path"; break;
case tNull: t = "null"; break;
case tAttrs: t = "attrs"; break;
case tList: t = "list"; break;
case tLambda:
case tPrimOp:
case tPrimOpApp:
t = "lambda";
break;
default: abort();
}
mkString(v, state.symbols.create(t));
}
/* Determine whether the argument is the null value. */
static void prim_isNull(EvalState & state, Value * * args, Value & v)
{
@ -108,7 +132,7 @@ static void prim_isFunction(EvalState & state, Value * * args, Value & v)
}
/* Determine whether the argument is an Int. */
/* Determine whether the argument is an integer. */
static void prim_isInt(EvalState & state, Value * * args, Value & v)
{
state.forceValue(*args[0]);
@ -116,7 +140,7 @@ static void prim_isInt(EvalState & state, Value * * args, Value & v)
}
/* Determine whether the argument is an String. */
/* Determine whether the argument is a string. */
static void prim_isString(EvalState & state, Value * * args, Value & v)
{
state.forceValue(*args[0]);
@ -124,7 +148,7 @@ static void prim_isString(EvalState & state, Value * * args, Value & v)
}
/* Determine whether the argument is an Bool. */
/* Determine whether the argument is a Boolean. */
static void prim_isBool(EvalState & state, Value * * args, Value & v)
{
state.forceValue(*args[0]);
@ -1189,6 +1213,7 @@ void EvalState::createBaseEnv()
// Miscellaneous
addPrimOp("import", 1, prim_import);
addPrimOp("__typeOf", 1, prim_typeOf);
addPrimOp("isNull", 1, prim_isNull);
addPrimOp("__isFunction", 1, prim_isFunction);
addPrimOp("__isString", 1, prim_isString);