Re: How to invert bool false/true in alias compose?

[mipri via Digitalmars-d-learn]

On Saturday, 7 December 2019 at 04:00:53 UTC, Marcone wrote:
import std;
alias cmd = compose!(to!bool, wait, spawnShell, to!string);

void main(){
        writeln(cmd("where notepad.exe"));
}


Result:

C:\Windows\System32\notepad.exe
C:\Windows\notepad.exe
false


The result show "false" because good spawnshell command return 
0 and 0 to bool is false. But I want to invert false to true to 
get true or false if command success.

These all work:

alias cmd = compose!(unaryFun!"!a", to!bool, wait, spawnShell, 
to!string);

alias cmd = compose!("!a", to!bool, wait, spawnShell, to!string);

alias cmd = compose!(b => !b, to!bool, wait, spawnShell, 
to!string);