TraceAbove
is an option for Trace and related functions which specifies whether to include evaluation chains which contain the evaluation chain containing the pattern form sought.
Details
- TraceAbove->True includes the first and last expressions in all evaluation chains within which the evaluation chain containing form occurs.
- TraceAbove->All includes all expressions in these evaluation chains.
- TraceAbove->{backward,forward} allows you to specify separately which expressions to include in the backward and forward directions.
- Using TraceAbove, you can see the complete paths by which expressions matching form arose during an evaluation.
Examples
open all close allBasic Examples (1)
Trace an evaluation showing only expressions with head Times:
f[x_, y_] := 2x yTrace[f[2, 3] + f[4, 5], _Times]Show the beginning and the end of the evaluation chain that leads to each expression with head Times:
Trace[f[2, 3] + f[4, 5], _Times, TraceAbove -> True]Scope (1)
A recursive definition for finding Fibonacci numbers:
fib[1] = fib[2] = 1;fib[n_] := fib[n - 1] + fib[n - 2];Show only the sums of fib that are encountered:
Trace[fib[4], fib[x_] + fib[y_]]Show the beginning and the end of the evaluation chain that leads to each sum of fib:
Trace[fib[4], fib[x_] + fib[y_], TraceAbove -> True]Show the entire evaluation chain that leads to each sum of fib:
Trace[fib[4], fib[x_] + fib[y_], TraceAbove -> All]Show the evaluation chain leading to the sum, but not what comes after the sum:
Trace[fib[4], fib[x_] + fib[y_], TraceAbove -> {All, False}]Text
Wolfram Research (1991), TraceAbove, Wolfram Language function, https://reference.wolfram.com/language/ref/TraceAbove.html.
CMS
Wolfram Language. 1991. "TraceAbove." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/TraceAbove.html.
APA
Wolfram Language. (1991). TraceAbove. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/TraceAbove.html