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get_interpreter

Definition: string s = get_interpreter(bool bQuote=false, object mb=machine_bits(), integer plat=platform(), bool bPrefW=false)
Description: Returns the full path and filename of a Phix executable, eg `C:\Program Files (x86)\Phix\pw.exe`, or "" if no suitable interpreter could be found.
pwa/p2js: Not supported.
Comments: You can find the implementation in builtins\get_interpreter.e (an autoinclude).

Things are usually much simpler when interpreting: there is a valid interpreter readily available in command_line()[1].
However, it also has to work when compiled, and not only on Windows/Linux, 32 and 64 bit, but also when run from anywhere.

It is important not to overly-rely on this routine working in situations over which you have no physical control. For instance, releasing a (pre-compiled) app which does not contain an interpreter (and builtins/ etc) and will therefore only work on systems where phix has previously been installed is unlikely to win you any customers, unless you give very clear instructions and/or use a failing get_interpreter() to trigger some kind of automatic download and installation.

bQuote: can be true (1) to add double quotes around results containing spaces.
mb: primarily for testing purposes, but there may also be cases where you specifically require a 32 or 64 bit interpreter, for example you might (as I do) only have a 32-bit libcurl.dll, so you need to fire off a 32bit interpreter to download some file with that, even when the main app is 64bit.
plat: likewise for testing purposes, only in this case of no practical use for anything else that I can think of.
bPrefW: causes the search to look for (eg) "pw.exe" before "p.exe" or vice versa, no real effect on Linux.

Should a bPrefW of -1 be specified, which is ok since it is a bool rather than a boolean, it is first replaced with true/false depending on whether the existing command_line()[1] contains a 'w'.

Note that an integer mb is advisory: if you ask for 32bit but all it can find is 64bit, it will return that, and vice versa, but at least it looks thoroughly. Should that be unacceptable, pass {32} or {64} to be more strict about the result. You can also (manually) create some or all of the files "pw64.exe","p64.exe","pw32.exe","p32.exe", "p64", and "p32", in any of the directories it looks in, to ensure it can find the one you need.
(In contrast, plat is never advisory: not that there is any need for it, or any overlap in the filenames it searches for.)
It searches the path from command_line(), cropped such that ../Phix/demo/.. -> ../Phix/, and current_dir() if different, plus anything in %PATH% that ends with "phix" or "bin" (case insensitive).
On Windows it also searches `C:\Program Files (x86)\Phix` and `C:\Program Files\Phix`.
On Linux it also searches %HOME%/phix.
Example: 
procedure run(string filename)
    string i = get_interpreter(true), -- eg `"C:\Program Files (x86)\Phix\p.exe"`
                                      -- or perhaps `/home/pete/phix/p` on Linux
         cmd = sprintf(`%s "%s"`,{i,filename})
    system(cmd)
end procedure

You could of course store it in a constant, or perhaps even better use it merely as a default for an overrideable system setting.
Implementation: See builtins\get_interpreter.e (an autoinclude) for details of the actual implementation.
See Also: command_line, requires, machine_bits, platform, system, system_exec