traceSeqN
lib.traceSeqN
Docs pulled from | This Revision | 22 minutes ago
Nixpkgs manual
Like traceSeq, but only evaluate down to depth n.
This is very useful because lots of traceSeq usages
lead to an infinite recursion.
Inputs
depth-
1. Function argument
x-
2. Function argument
y-
3. Function argument
Type
traceSeqN :: Int -> a -> b -> b
Examples
lib.debug.traceSeqN usage example
traceSeqN 2 { a.b.c = 3; } null
trace: { a = { b = {…}; }; }
=> null
Noogle detected
Implementation
The following is the current implementation of this function.
traceSeqN =
depth: x: y:
let
snip =
v:
if isList v then
noQuotes "[…]" v
else if isAttrs v then
noQuotes "{…}" v
else
v;
noQuotes = str: v: {
__pretty = const str;
val = v;
};
modify =
n: fn: v:
if (n == 0) then
fn v
else if isList v then
map (modify (n - 1) fn) v
else if isAttrs v then
mapAttrs (const (modify (n - 1) fn)) v
else
v;
in
trace (generators.toPretty { allowPrettyValues = true; } (modify depth snip x)) y;