Lua Notes: Run scripts

Run nelua 'scripts' - out of the box

Strictly speaking, this works right away:

#! /usr/bin/env nelua
print('a script?')

Usage, when this is in an executable file named 'script':

$ ./script
a script?

You can also pass one flag to a fixed path:

#! /usr/local/bin/nelua --cc=tcc
print('a script?')

But, the performance isn't nearly what you'd expect from competitors like rdmd or nimcr, even with the caching. For example:

$ nelua -o bin -i 'print "a script?"'; hyperfine -N --warmup=3 ./bin ./script 'perl -le "print \"a script?"\"'
Benchmark 1: ./bin
  Time (mean ± σ):       2.5 ms ±   0.2 ms    [User: 1.2 ms, System: 1.0 ms]
  Range (min … max):     1.8 ms …   3.5 ms    1554 runs
 
Benchmark 2: ./script
  Time (mean ± σ):     186.4 ms ±   5.5 ms    [User: 138.1 ms, System: 43.0 ms]
  Range (min … max):   179.4 ms … 194.3 ms    16 runs
 
Benchmark 3: perl -le "print \"a script?"\"
  Time (mean ± σ):       8.2 ms ±   0.5 ms    [User: 1.9 ms, System: 5.7 ms]
  Range (min … max):     6.3 ms …   9.6 ms    418 runs
 
Summary
  './bin' ran
    3.22 ± 0.37 times faster than 'perl -le "print \"a script?"\"'
   73.67 ± 7.43 times faster than './script'

Why is it so slow? Because Lua always runs:

$ cat script
#! /usr/bin/env nelua
print('a script?')
## print('preprocessor running')
$ ./script ; ./script ; ./script ; ./script
preprocessor running
a script?
preprocessor running
a script?
preprocessor running
a script?
preprocessor running
a script
$ ~/.cache/nelua/script ; ~/.cache/nelua/script
a script?
a script?

$ stat -c%Y ~/.cache/nelua/script
1697672209
$ ./script
preprocessor running
a script?
$ stat -c%Y ~/.cache/nelua/script
1697672209
$ echo 'print("a change")' >> script
$ ./script
preprocessor running
a script?
a change
$ stat -c%Y ~/.cache/nelua/script
1697672219