I decided to give the elvish shell a try today. Elvish is a shell written in golang, designed to be more expressive than bash.
Bash drops just short of being a programming language. For example, it doesn’t do floating point arithmetic, which is a nuisance. Elvish does, though.
I set myself a little task: write a program which reads from standard in, prints the number of lines read, then prints the input. It’s an interesting task because it must cache the input.
Here’s what I cam up with in elvish:
#!/usr/bin/env elvish
contents = [(cat )]
echo (count $contents)
for line $contents { echo $line }
Here’s the equivalent I write in awk:
{
i += 1;
line[i] = $0;
}
END{
print i;
for(idx=0; idx<i; idx++) print line[idx];
}
As you can see, elvish manages the same thing in less than half the number of lines.
Here’s my C++ version:
#include <iostream>
#include <string>
#include <vector>
int main()
{
std::vector<std::string> lines;
std::string line;
int nlines = 0;
while(std::getline(std::cin, line)) {
nlines++;
lines.push_back(line);
}
std::cout << nlines << "\n";
for(std::vector<std::string>::iterator it = lines.begin(); it != lines.end(); ++it)
std::cout << *it << "\n";
return 0;
}
That’s 20 lines of code.
Here are the timings of running the scripts:
time awk -f count.awk <derive-2.txt >/dev/null real 0m0.067s user 0m0.004s sys 0m0.002s Although there are some odd timings: time awk -f count.awk <derive-2.txt >/dev/null real 0m0.006s user 0m0.003s sys 0m0.002s
$time elvish count <derive-2.txt >/dev/null real 0m0.052s user 0m0.025s sys 0m0.011s
time ./a.out < derive-2.txt >/dev/null # c++ version real 0m0.006s user 0m0.004s sys 0m0.001s
Awk seemed a little inconsistent in its performance. I’m not sure what’s going on there. It looks like Awk can be a real speed demon, and I’ve even seen it run a little faster than the C++ code. Those Awk guys certainly seem to know how to optimise stuff.
Elvish is certainly worth checking out. I’m not sure about its runtime speed, though.
