As I remembered 'tick' from FIG-Forth, it could be used without abortion when a word wasn't in the wordlist:
' the_word
gave a reference to the word if it was in the word-list and gave 'false' otherwise.
Is it possible to construct something like that in ANS Forth to be used with [if], [then] and [else]?
I guess something like this:
: tick ( a u -- xt|f ) bl word find 0= if drop 0 then ;
The FIG-Forth document says:
Leaves the parameter field address of dictionary word nnnn. As a
compiler directive, executes in a colon-definition to compile the
address as a literal. If the word is not found after a search of
CONTEXT and CURRENT, an appropriate error message is given.
Although it is entirely possible the version of FIG-Forth you where using did not abide by the standard, and returned false.
Related
The following is my sample code: https://play.openpolicyagent.org/p/oyY1GOsYaf
Here when I try to evaluate names array, it is showing:
error occurred: 1:1: rego_unsafe_var_error: var names is unsafe
But when I define the same comprehension outside the allow rule definition : https://play.openpolicyagent.org/p/Xv0cF7FM8b, I am able to evaluate the selection
[
"smoke",
"dev"]
could someone help me to point out the difference and if I want to define the comprehention inside the rule is there any syntax I need to follow? Thanks in advance
Note: I am getting the final output as expected in both cases, only issue is with the names array evaluation.
The way the Rego Playground generates a query when evaluating a selection is much more simplistic than one might assume. A query will be generated from your selected text, without taking into account where in the document that text was selected. This means that even if you select a local variable inside a rule body, the query will simply contain that variable name (names, in your case); which will be perceived as a reference to a top-level variable in the document's body, even though a rule-local variable was selected. This is why your first sample returns an error, as there is no top-level variable names in the document; whereas the second sample does, and therefore succeeds.
You can test this quirk by selecting and evaluating the word hello on line 3 here: https://play.openpolicyagent.org/p/n5OPoFnlhx.
package play
# hello
hello {
m := input.message
m == "world"
}
Even though it's just part of a comment, it'll evaluate just as if you had selected the rule name on line 5.
I am a newcomer to coding in general and I want to learn basic Lua scripting for my own hobby.
After working on a Lua script, the syntax all seems to be without error but I have come across one issue that I don't understand, I broke it down to this basic function:
{$lua}
ID1 = "10"
ID2 = "0"
if (ID1 ~= nil and ID1 == "10") then
writeInteger(ID2,"25")
end
print(ID2)
The issue is that the writeInteger does not seem to work at all, ID2 remains at value "0" while it should become "25".
Any help would be greatly appreciated.
This is not valid Lua, or at least it isn't valid vanilla (out-of-the-box) Lua, and since you have not specified anything else, there is not much we can do to help. I will assume writeInteger is a valid function (since your interpreter isn't complaining about a call to a nil value), but I don't think it works as you expect.
If you want to set the ID2 variable to 25, simply write:
ID2 = 25
Lua will convert the string type to an integer type automatically. You can run print(type(ID2)) to confirm this
If you are using cheat engine (as a quick google search suggests) the writeInteger function requires an address and a value.
function writeInteger(Address, Value): Boolean - Returns true on success.
I am not sure if ID2, a Lua variable, is a valid address, but I am sure that "25" is not an integer. You should remove the quotation marks to start, and since the function returns a boolean you can see if the function was successful by doing:
print(writeInteger(ID2, 25))
Lua uses pass by value for primitive types like numbers, booleans and strings. So if you pass a number to a function like writeInteger, it creates a local copy within the function. The function can alter this copy but it will have no effect on caller (of writeInteger in this case). I don't know how writeInteger is supposed to work but if you want to call a function which alters its argument you can create a table and pass that. Tables are still passed by value but the "value" of a table is its memory address (so in effect tables are passed by reference and you can alter the contents of a table by passing it to a function).
See more here
Function/variable scope (pass by value or reference?)
I've got a file with syntactically correct Lua 5.1 source code.
I've got a position (line and character offset) inside that file.
I need to get an offset in bytes to the closing parenthesis of the innermost function() body that contains that position (or figure out that the position belongs to the main chunk of the file).
I.e.:
local function foo()
^ result
print("bar")
^ input
end
local foo = function()
^ result
print("bar")
^ input
end
local foo = function()
return function()
^ result
print("bar")
^ input
end
end
...And so on.
How do I do that robustly?
EDIT: My original answer did not take into account the "innermost" requirement. I've since taken that into account
To make things "robust," there are a few considerations.
First of all, it's important that you skip over string and comment contents, to avoid incorrect output in situations like:
foo = function()
print(" function() ")
-- function()
print("bar")
^ input
end
This can be somewhat difficult, considering Lua's nested string and comment syntax. Consider, for example, a situation where the input begins in a nested string or comment:
foo = function()
print([[
bar = function()
print("baz")
^ input
end
]])
end
Consequently, if you want a completely robust system, it is not acceptable to only parse backwards until you hit the end of a function parameter list, because you may not have parsed backwards far enough to reach a [[ which would invalidate your match. It is therefore necessary to parse the entire file up to your position (unless you're okay with incorrect matches in these weird situations. If this is an editor plugin, these "incorrect" results may actually be desirable, because they would allow you to edit lua code which is stored in string literal form inside other lua code using the same plugin).
Because the particular syntax that you're trying to match doesn't have any kind of "nesting", a full-blown parser isn't needed. You will need to maintain a stack, however, to keep track of scope. With that in mind, all you need to do is step through the source file character-by-character from the beginning, applying the following logic:
Every time a " or ' is encountered, ignore the characters up to the closing " or '. Be careful to handle escapes like \" and \\
Every time a -- is encountered, ignore the characters up to the closing newline for the comment. Be careful to only do this if the comment is not a multiline comment.
Every time a multiline string opening symbol is encountered (such as [[, [=[, etc), or a multiline comment symbol is encountered (such as --[[ or --[=[, etc) ignore the characters up until the closing square brackets with the proper number of matching equals signs between them.
When a word boundary is encountered check to see if the characters after it could begin a block which ends with an end (for example, if, while, for, function, etc. DO NOT include repeat). If so, push the position on the scope stack. A "word boundary" in this case is any character which could not be used a lua identifier (this is to prevent matches in cases like abcfunction()). The beginning of the file is also considered a word boundary.
If a word boundary is encountered and it is followed by end, pop the top element of the stack. If the stack has no elements, complain about a syntax error.
When you finally step forward and reach your "input" position, pop elements from the stack until you find a function scope. Step forward from that position to the next ), ignoring )'s in comments (which could theoretically be found in an argument list if it spans multiple lines or contains inline --[[ ]] comments). That position is your result.
This should handle every case, including situations where the function syntactic sugar is used, like
function foo()
print("bar")
end
which you did not include in your example but which I imagine you still want to match.
I am relatively new to maxima. I want to know how to write an array into a text file using maxima.
I know it's late in the game for the original post, but I'll leave this here in case someone finds it in a search.
Let A be a Lisp array, Maxima array, matrix, list, or nested list. Then:
write_data (A, "some_file.data");
Let S be an ouput stream (created by openw or opena). Then:
write_data (A, S);
Entering ?? numericalio at the input prompt, or ?? write_ or ?? read_, will show some info about this function and related ones.
I've never used maxima (or even heard of it), but a little Google searching out of curiousity turned up this: http://arachnoid.com/maxima/files_functions.html
From what I can gather, you should be able to do something like this:
stringout("my_new_file.txt",values);
It says the second parameter to the stringout function can be one or more of these:
input: all user entries since the beginning of the session.
values: all user variable and array assignments.
functions: all user-defined functions (including functions defined within any loaded packages).
all: all of the above. Such a list is normally useful only for editing and extraction of useful sections.
So by passing values it should save your array assignments to file.
A bit more necroposting, as google leads here, but I haven't found it useful enough. I've needed to export it as following:
-0.8000,-0.8000,-0.2422,-0.242
-0.7942,-0.7942,-0.2387,-0.239
-0.7776,-0.7776,-0.2285,-0.228
-0.7514,-0.7514,-0.2124,-0.212
-0.7168,-0.7168,-0.1912,-0.191
-0.6750,-0.6750,-0.1655,-0.166
-0.6272,-0.6272,-0.1362,-0.136
-0.5746,-0.5746,-0.1039,-0.104
So I've found how to do this with printf:
with_stdout(filename, for i:1 thru length(z_points) do
printf (true,"~,4f,~,4f,~,4f,~,3f~%",bot_points[i],bot_points[i],top_points[i],top_points[i]));
A bit cleaner variation on the #ProdoElmit's answer:
list : [1,2,3,4,5]$
with_stdout("file.txt", apply(print, list))$
/* 1 2 3 4 5 is then what appears in file.txt */
Here the trick with apply is needed as you probably don't want to have square brackets in your output, as is produced by print(list).
For a matrix to be printed out, I would have done the following:
m : matrix([1,2],[3,4])$
with_stdout("file.txt", for row in args(m) do apply(print, row))$
/* 1 2
3 4
is what you then have in file.txt */
Note that in my solution the values are separated with spaces and the format of your values is fixed to that provided by print. Another caveat is that there is a limit on the number of function parameters: for example, for me (GCL 2.6.12) my method does not work if length(list) > 64.
I would like to use FORTRAN streaming I/O to make a program that tells me how many lines a text-file has. The idea is to make something like this:
OPEN(UNIT=10,ACCESS='STREAM',FILE='testfile.txt')
nLines=0
bContinue=.TRUE.
DO WHILE (bContinue)
READ(UNIT=10) cCharacter
IF (cCharacter.EQ.{EOL-char}) nLines=nLines+1
IF (cCharacter.EQ.{EOF-char}) bContinue=.FALSE.
ENDDO
(I didn't include variable declaration but I think you get the idea of what they are; the only important clarification would be that that cCharacter has LEN=1)
My problem is that I don't know how to check if the character I just read from the file is an end-of-line or end-of-file (the "ifs" in the code). When you read and print characters this way, you eventually get newlines in the same place you had them in the original text, so I think it does read and recognize them as "characters", somehow. Perhaps turning the characters into integers and comparing to the appropriate number? Or is there a more direct way?
(I know that you can use the register reading (EDIT: I meant record reading) to do a program that reads lines more easily and add an IOstatus to check for eof, but the "line counter" is just a useful example, the idea is to learn how to move in a more controlled way through a textfile)
Checking for a specific character as line terminator makes you program OS dependent. It would be better to use the facilities of the language so that your program is compiler and OS dependent. Since lines are basically records, why do this with steam I/O? That request seems to make an easy job into a hard one. If are can use regular IO, here is an example program to count the lines in a text file.
EDIT: the code fragment was changed into a program to answer questions in the comments. With "line" as a character variable, when I test the program with gfortran and ifort I don't see a problem when the input file has empty or blank lines.
program test_lc
use, intrinsic :: iso_fortran_env
integer :: LineCount, Read_Code
character (len=200) :: line
open (unit=51, file="temp.txt", status="old", access='sequential', form='formatted', action='read' )
LineCount = 0
ReadLoop: do
read (51, '(A)', iostat=Read_Code) line
if ( Read_Code /= 0 ) then
if ( Read_Code == iostat_end ) then
exit ReadLoop ! end of file --> line count found
else
write ( *, '( / "read error: ", I0 )' ) Read_Code
stop
end if
end if
LineCount = LineCount + 1
write (*, '( I0, ": ''", A, "''" )' ) LineCount, trim (line)
if ( len_trim (line) == 0 ) write (*, '("The above is an empty or all blank line.")' )
end do ReadLoop
write (*, *) "found", LineCount, " lines"
end program test_lc
If you want to do further processing of the file, you can rewind it.
P.S.
The main reason that I have used Fortran Stream IO is to read files produced by other languages, e.g., C
Portable methods are provided to write new-line boundaries; I'm not aware of a portable method to test for such.