There are three benchmarks in benchmark_test.go that compare the performance of go-restructure to that of the standard library regexp package. go-restructure uses a very slightly modified version of the regexp package so the performance of the core regular expression evaluator is very similar; most of the difference is therefore associated with the overhead of reflection.
These benchmarks were computed using go test -bench=. on an 2.8 GHz Intel Core i7 processor running OSX 10.10.5.
The first benchmark involves finding the first floating point number in a string of a few thousand characters. go-restructure takes around 8% longer than the standard library:
go-restructure 32428 ns/op
stdlib/regexp 30060 ns/op
The second benchmark involves parsing a short email address. go-restructure takes around
40% longer than the standard library:
go-restructure 1188 ns/op
stdlib/regexp 844 ns/op
The third benchmark involves finding all python import statements in a file of around one hundred lines of python source. go-restructure takes around 2x longer than the standard library:
go-restructure 695 ns/op
stdlib/regexp 337 ns/op
The high overhead for go-restructure on the last benchmark is probably due to go-restructure allocating a struct to hold the results of each match found by FindAll. In most cases this performance overhead will be a small price to pay for composable, inspectable regular expressions, particularly when it amonuts to the difference between one third of a microsecond and two thirds of a microsecond. However, applications that execute a very large number of regular expressions for which performance is critical may be well advised to use the standard library regexp package directly.