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trace                                                       (Feedback)
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trace : string * int -> ('a -> 'b) -> 'a -> 'b

SYNOPSIS
Invoke a function with a specified level of tracing.

KEYWORDS
Tracing.

DESCRIBE
The {trace} function is used to set the value of a tracing variable
for the duration of one top-level function call.

A call to {trace (nm,i) f x} attempts to set the tracing variable
associated with the string {nm} to value {i}.  Then it evaluates
{f x} and returns the resulting value after restoring the
trace level of {nm}.

FAILURE
Fails if the name given is not associated with a registered tracing
variable. Also fails if the function invocation fails.

EXAMPLE

- load "mesonLib";

- trace ("meson",2) prove
     (concl SKOLEM_THM,mesonLib.MESON_TAC []);

0 inferences so far. Searching with maximum size 0.
0 inferences so far. Searching with maximum size 1.
Internal goal solved with 2 MESON inferences.
0 inferences so far. Searching with maximum size 0.
0 inferences so far. Searching with maximum size 1.
Internal goal solved with 2 MESON inferences.
0 inferences so far. Searching with maximum size 0.
0 inferences so far. Searching with maximum size 1.
Internal goal solved with 2 MESON inferences.
0 inferences so far. Searching with maximum size 0.
0 inferences so far. Searching with maximum size 1.
Internal goal solved with 2 MESON inferences.
  solved with 2 MESON inferences.

> val it = |- !P. (!x. ?y. P x y) = ?f. !x. P x (f x) : thm

- traces();

> val it =
    [{default = 1, name = "meson", trace_level = 1},
     {default = 10, name = "Subgoal number", trace_level = 10},
     {default = 0, name = "Rewrite", trace_level = 0},
     {default = 0, name = "Ho_Rewrite", trace_level = 0}]




SEEALSO
Feedback, Feedback.register_trace, Feedback.reset_trace,
Feedback.reset_traces, Feedback.set_trace, Feedback.traces,
Lib.with_flag.

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