TakeV
/
guix
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Adding tryEval builtin. It allows to catch presence of errors in an expression.

This commit is contained in:
Michael Raskin 2009-08-25 16:06:46 +00:00
parent 5e9a4e5101
commit 3bca8931e8
1 changed files with 18 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
src/libexpr/primops.cc
View File

@ -223,6 +223,23 @@ static Expr prim_addErrorContext(EvalState & state, const ATermVector & args)
}
}
/* Try evaluating the argument. Success => {success=true; value=something;},
* else => {success=false; value=false;} */
static Expr prim_tryEval(EvalState & state, const ATermVector & args)
{
ATermMap res = ATermMap();
try {
Expr val = evalExpr(state, args[0]);
res.set(toATerm("value"), makeAttrRHS(val, makeNoPos()));
res.set(toATerm("success"), makeAttrRHS(eTrue, makeNoPos()));
} catch (Error & e) {
printMsg(lvlInfo, format("tryEval caught an error: %1%: %2%") % e.prefix() % e.msg());
res.set(toATerm("value"), makeAttrRHS(eFalse, makeNoPos()));
res.set(toATerm("success"), makeAttrRHS(eFalse, makeNoPos()));
}
return makeAttrs(res);
}
/* Return an environment variable. Use with care. */
static Expr prim_getEnv(EvalState & state, const ATermVector & args)
@ -1020,6 +1037,7 @@ void EvalState::addPrimOps()
addPrimOp("abort", 1, prim_abort);
addPrimOp("throw", 1, prim_throw);
addPrimOp("__addErrorContext", 2, prim_addErrorContext);
addPrimOp("__tryEval", 1, prim_tryEval);
addPrimOp("__getEnv", 1, prim_getEnv);
addPrimOp("__trace", 2, prim_trace);