OpenEuphoria

Re: eval() function

• Posted by Alex Chamberlain <alex.chamberlain at tiscali.co.uk> Nov 02, 2005
• 595 views

Thanks Juergen - amazing mind! I don't think I made it clear that I need the
script to evaluate full Euphoria programs!
I have adapted your script to run it my way.

--eval.e

include misc.e

global constant
EVAL_PROG_NAME = "eval_prg.tmp",
EVAL_RES_NAME = "eval_res.tmp",
EVAL_ERR_RET = -1,
EVAL_WRITE_ERR = 1,
EVAL_READ_ERR  = 2

global integer EVAL_ERROR

EVAL_ERROR = 0

global function eval (sequence script)
	sequence plat, ret
	integer tmp_fn -- , sys
	object line

	-- write a temporary program for evaluating the expression and
	-- writing the result to another temporary file
	tmp_fn = open(EVAL_PROG_NAME, "w")
	if tmp_fn = -1 then
		EVAL_ERROR = EVAL_WRITE_ERR
		return EVAL_ERR_RET
	end if
	
	puts(tmp_fn, script)
	close(tmp_fn)

	-- run the temporary program
	if platform() = DOS32 then
		plat = "ex"
	elsif platform() = WIN32 then
		plat = "exw"
	elsif (platform() = LINUX) or (platform() = FREEBSD) then
		plat = "exu"
	end if
	system(plat & " " & EVAL_PROG_NAME & " > " & EVAL_RES_NAME, 0)

	-- read the content of the temporary result file,
	-- and convert it to a number
	tmp_fn = open(EVAL_RES_NAME, "r")
	if tmp_fn = -1 then
		EVAL_ERROR = EVAL_READ_ERR
		return EVAL_ERR_RET
	end if

	ret = {}
	while 1 do
		line = gets(tmp_fn)
		if atom(line) then
			exit
		end if
		ret &= line
	end while
	close(tmp_fn)

	-- delete temporary files
	system("DEL *.tmp", 0)

	return ret
end function

--demo.ex

include eval.e
include get.e

sequence script
object ret

-- Define the script contents - any Euphoria code!
script = "puts(1, \"This is this result of the demo eval script!\")"

procedure handleReturn(object ret)
	puts(1, "The script output the following:\n" & ret)
end procedure

ret = eval(script)

if atom(ret) then
	if EVAL_ERROR = 0 then
		handleReturn(ret)
	elsif EVAL_ERROR = EVAL_WRITE_ERR then
		puts(1, "Sorry, there was a write error whilst evaluating the script")
	elsif EVAL_ERROR = EVAL_READ_ERR then
		puts(1, "Sorry, there was a read error whilst evaluating the script")
	end if
else
	handleReturn(ret)
end if

abort(wait_key()*0)

The only problem is that the Windows program doesn't like redirecting its input
(can others please try it!) and it hasn't been run on Linux/FreeBSD yet. It work
on DOS fine so there you go. On the web very soon, and is running up to my CGI
interpretor.

Thanks,
 Alex