I'm trying to write down 6809 assembly in EBNF to write a tree-sitter parser.
I'm stuck on one certain production. In 6809 assembly, you can use a register as an operand and additionally de- or increment it:
LDA 0,X+ ; loads A from X then bumps X by 1
LDD ,Y++ ; loads D from Y then bumps Y by 2
LDA 0,-U ; decrements U by 1 then loads A from address in U
LDU ,--S ; decrements S by 2 then loads U from address in S
Mind the "missing" first operand in the second line of code. Here are the productions I wrote:
instruction = opcode, [operand], ["," , register_exp];
...
register_exp = [{operator}], register | register, [{operator}];
register = "X" | "Y" | "U" | etc. ;
operator = "+" | "-";
The problem is register_exp = .... I feel like there could be a more elegant way to define this production. Also, what happens if only a register is given to register_exp?
You probably need
register_exp = [{operator}], register | register, [{operator}] | register;
to allow register names without operators. Why do you find it not so elegant? Quite descriptive.
Related
I need to build a lexical analyzer using Gocc, however no option to ignore case is mentioned in the documentation and I haven't been able to find anything related. Anyone have any idea how it can be done or should I use another tool?
/* Lexical part */
_digit : '0'-'9' ;
int64 : '1'-'9' {_digit} ;
switch: 's''w''i''t''c''h';
while: 'w''h''i''l''e';
!whitespace : ' ' | '\t' | '\n' | '\r' ;
/* Syntax part */
<<
import(
"github.com/goccmack/gocc/example/calc/token"
"github.com/goccmack/gocc/example/calc/util"
)
>>
Calc : Expr;
Expr :
Expr "+" Term << $0.(int64) + $2.(int64), nil >>
| Term
;
Term :
Term "*" Factor << $0.(int64) * $2.(int64), nil >>
| Factor
;
Factor :
"(" Expr ")" << $1, nil >>
| int64 << util.IntValue($0.(*token.Token).Lit) >>
;
For example, for "switch", I want to recognize no matter if it is uppercase or lowercase, but without having to type all the combinations. In Bison there is the option % option caseless, in Gocc is there one?
Looking through the docs for that product, I don't see any option for making character literals case-insensitive, nor do I see any way to write a character class, as in pretty well every regex engine and scanner generator. But nothing other than tedium, readability and style stops you from writing
switch: ('s'|'S')('w'|'W')('i'|'I')('t'|'T')('c'|'C')('h'|'H');
while: ('w'|'W')('h'|'H')('i'|'I')('l'|'L')('e'|'E');
(That's derived from the old way of doing it in lex without case-insensitivity, which uses character classes to make it quite a bit more readable:
[sS][wW][iI][tT][cC][hH] return T_SWITCH;
[wW][hH][iI][lL][eE] return T_WHILE;
You can come closer to the former by defining 26 patterns:
_a: 'a'|'A';
_b: 'b'|'B';
_c: 'c'|'C';
_d: 'd'|'D';
_e: 'e'|'E';
_f: 'f'|'F';
_g: 'g'|'G';
_h: 'h'|'H';
_i: 'i'|'I';
_j: 'j'|'J';
_k: 'k'|'K';
_l: 'l'|'L';
_m: 'm'|'M';
_n: 'n'|'N';
_o: 'o'|'O';
_p: 'p'|'P';
_q: 'q'|'Q';
_r: 'r'|'R';
_s: 's'|'S';
_t: 't'|'T';
_u: 'u'|'U';
_v: 'v'|'V';
_w: 'w'|'W';
_x: 'x'|'X';
_y: 'y'|'Y';
_z: 'z'|'Z';
and then explode the string literals:
switch: _s _w _i _t _c _h;
while: _w _h _i _l _e;
I need to create a new variable based on 3 variables.
If someone is coded as 1 against any 1 of 3 variables, they are coded as 1 in the new variable
If they don’t code 1 on any variable, but code as 2 against any 1 of 3 variables they are coded as 2 in the new variable
Everything else is coded as 99
In syntax, I’ve written this as:
IF (Keep_Any=1 OR Find_Any=1 OR Improve_Any=1) Keep_Find_Improve=1.
IF ((Keep_Find_Improve~= 1) & (Keep_Any=2 | Find_Any=2 | Improve_Any=2)) Keep_Find_Improve=2.
IF (Keep_Find_Improve~=1 & Keep_Find_Improve~=2) Keep_Find_Improve=99.
EXECUTE.
However, the first part correctly identifies cases coded as 1, but the rest of the syntax doesn't work. This is in despite of using some syntax that uses the exact same logic on other variables:
COMPUTE Keep_Any= Q9a_recoded = 1 | Q9b_recoded = 1 | Q9c_recoded = 1.
EXECUTE.
IF (Q9A_recoded=1 OR Q9B_recoded=1 OR Q9C_recoded=1) Keep_Any=1.
IF ((Keep_Any~=1) & (Q9A_recoded= 2 OR Q9B_recoded=2 OR Q9C_recoded=2)) Keep_Any=2.
IF (Keep_Any~=1 & Keep_Any~=2) Keep_Any=99.
EXECUTE.
Does anyone have any ideas of why this is happening and how to fix it?
Try:
COMPUTE Target1=99.
COMPUTE Target1=ANY(2, V1, V2, V3).
COMPUTE Target1=ANY(1, V1, V2, V3).
Or better still (more efficient, even if more lines of code)
DO IF ANY(1, V1, V2, V3)=1.
COMPUTE Target2= 1.
ELSE IF ANY(2, V1, V2, V3)=1.
COMPUTE Target2 = 2.
ELSE.
COMPUTE Target2=99.
END IF.
The reason your syntax isn't working is the second condition you are using:
IF ((Keep_Find_Improve~= 1) & ...
When the first condition wasn't met, Keep_Find_Improve is still missing, and therefore doesn't meet the condition of ~=1.
The same thing goes later for IF (Keep_Any~=1 & Keep_Any~=2).
So you shouldn't be comparing Keep_Find_Improve to 1 or 2, you should be checking if it has received a value or if it's still missing:
IF (Keep_Any=1 OR Find_Any=1 OR Improve_Any=1) Keep_Find_Improve=1.
IF (missing(Keep_Find_Improve) & (Keep_Any=2 | Find_Any=2 | Improve_Any=2)) Keep_Find_Improve=2.
IF missing(Keep_Find_Improve) Keep_Find_Improve=99.
* alternatively: recode Keep_Find_Improve(miss=99).
EXECUTE.
All this being said, I recommend you use the more advanced code suggested by #JigneshSutar.
My goal is to write a string to a file where the size of the string will vary. At the moment I have made the string very large so that there is no overflow but is there a way to make it so that the size of the string is the exact number of characters I'm placing into it? I've tried something like the code below but it gives me an error unknown identifier "address count" I think it is because address count is a variable declared in a process and address count is constantly changing. Is there any way around this?
signal address_map :string (1 to address_count);
many thanks
leo
"My goal is to write a string to a file." Hence, lets just focus on that.
Step 1: reference the file IO packages (recommended to turn on VHDL-2008):
use std.textio.all ;
-- use ieee.std_logic_textio.all ; -- include if not using VHDL-2008
Step 2: Declare your file
file MyFile : TEXT open WRITE_MODE is "MyFile.txt";
Step 3: Create a buffer:
TestProc : process
variable WriteBuf : line ;
begin
write ... -- see step 4
writeline ... -- see step 5
Step 4: Use write to write into the buffer (in the process TestProc):
write(WriteBuf, string'("State = ") ) ; -- Any VHDL version
write(WriteBuf, StateType'image(State)) ;
swrite(WriteBuf, " at time = " ); -- VHDL-2008 simplification
write(WriteBuf, NOW, RIGHT, 12) ;
Step 5: Write the buffer to the file (in the process TestProc):
writeline(MyFile, WriteBuf) ;
Alternate Steps 3-5: Use built-in VHDL Write with to_string:
Write(MyFile, "State = " & to_string(State) &
", Data = " & to_hstring(Data) &
" at time " & to_string(NOW, 1 ns) ) ;
Alternate Steps 1-5: Use OSVVM (see http://osvvm.org) (requires VHDL-2008):
library osvvm ;
use osvvm.transcriptpkg.all ; -- all printing goes to same file
. . .
TestProc : process
begin
TranscriptOpen("./results/test1.txt") ;
Print("State = " & to_string(State) &
", Data = " & to_hstring(Data) &
" at time " & to_string(NOW, 1 ns) ) ;
One hard but flexible solution is to use dynamic allocation features of VHDL (copied from ADA).
You have to use an access of string (it is roughly like a "pointer to a string" in C)
type line is access string;
you event don't have to do it because line is already declared in std.textio package.
Ok, the problem next is that you can't use an access type for a signal, so you have to use a shared variable:
shared variable address_map: line;
And finally you have to allocate, read and write to this line:
--Example in a function/procedure/process:
--free a previously allocated string:
if address_map /= NULL then
deallocate(address_map);
end if;
--allocate a new string:
address_map:=new string (1 to address_count);
address_map(1 to 3):="xyz";
--we have here:
-- address_map(1)='y'
-- address_map(2 to 3)="yz"
-- address_map.all = "xyz"
Notice the use of new/deallocate (like malloc/free in C or free/delete in C++).
It is not easy to handle this kind of code, I recommend you to read the documentation of VHDL keywords "new", "deallocate" and "access" (easily found with your favorite search engine) or feel free to ask more questions.
You can also use the READ (read the whole line into a string) and WRITE (append a string to the line) functions from std.textio package.
I am working with Graphchi's pagerank example: https://github.com/GraphChi/graphchi-cpp/wiki/Example-Apps#pagerank-easy
The example app writes a binary file with vertex information that I would like to read/convert to a plan text file (to later call into R or some other language).
The documentation states that:
"GraphChi will write the values of the edges in a binary file, which is easy to handle in other programs. Name of the file containing vertex values is GRAPH-NAME.4B.vout. Here "4B" refers to the vertex-value being a 4-byte type (float)."
The 'easy to handle' part is what I'm struggling with - I have experience with high level languages but not C++ or dealing with binary files. I have found a few things through searching stackoverflow but no luck yet in reading this file. Ideally this would be done through bash or python.
thanks very much for your help on this.
Update: hexdump graph-name.4B.vout | head -5 gives:
0000000 999a 3e19 7468 3e7f 7d2a 3e93 d8e0 3ec4
0000010 cec6 3fe4 d551 3f08 eff2 3e54 999a 3e19
0000020 999a 3e19 3690 3e8c 0080 3f38 9ea3 3ef5
0000030 b7d6 3f66 999a 3e19 10e3 3ee1 400c 400d
0000040 a3df 3e7c 999a 3e19 979c 3e91 5230 3f18
Here is example code how you can use GraphCHi to write the output out as a string:
https://github.com/GraphChi/graphchi-cpp/wiki/Vertex-Aggregators
But the array is simple byte array. Here is example how to read it in python:
import struct
from array import array as binarray
import sys
inputfile = sys.argv[1]
data = open(inputfile).read()
a = binarray('c')
a.fromstring(data)
s = struct.Struct("f")
l = len(a)
print "%d bytes" %l
n = l / 4
for i in xrange(0, n):
x = s.unpack_from(a, i * 4)[0]
print ("%d %f" % (i, x))
I was having the same trouble. Luckily I work with a bunch of network engineers who helped me out! On Mac Linux, the following command works to print the 4B.vout data one line per node, with the integer values the same as is given in the summary file. If your file is called eg, filename.4B.vout, then some command line perl gets you:
cat filename.4B.vout | LANG= perl -0777 -e '$,=\"\n\"; print unpack(\"L*\",<>),\"\";'
Edited to add: this is for the assignments of connected component ID and community ID, written implicitly the 1st line is the ID of the node labeled 0, the 2nd line is the node labeled 1 etc. But I am copypasting here so I'm not sure how it would need to change for floats. It works great for the integer values per node.
I'm trying to implement a PID controller following http://en.wikipedia.org/wiki/PID_controller
The mechanism I try to control works as follows:
1. I have an input variable which I can control. Typical values would be 0.5...10.
2. I have an output value which I measure daily. My goal for the output is roughly at the same range.
The two variables have strong correlation - when the process parameter goes up, the output generally goes up, but there's quite a bit of noise.
I'm following the implementation here:
http://code.activestate.com/recipes/577231-discrete-pid-controller/
Now the PID seems like it is correlated with the error term, not the measured level of output. So my guess is that I am not supposed to use it as-is for the process variable, but rather as some correction to the current value? How is that supposed to work exactly?
For example, if we take Kp=1, Ki=Kd=0, The process (input) variable is 4, the current output level is 3 and my target is a value of 2, I get the following:
error = 2-3 = -1
PID = -1
Then I should set the process variable to -1? or 4-1=3?
You need to think in terms of the PID controller correcting a manipulated variable (MV) for errors, and that you need to use an I term to get to an on-target steady-state result. The I term is how the PID retains and applies memory of the prior behavior of the system.
If you are thinking in terms of the output of the controller being changes in the MV, it is more of a 'velocity form' PID, and the memory of prior errors and behavior is integrated and accumulated in the prior MV setting.
From your example, it seems like a manipulated value of -1 is not feasible and that you would like the controller to suggest a value like 3 to get a process output (PV) of 2. For a PID controller to make use of "The process (input) variable is 4,..." (MV in my terms) Ki must be non-zero, and if the system was at steady-state, whatever was accumulated in the integral (sum_e=sum(e)) would precisely equal 4/Ki, so:
Kp= Ki = 1 ; Kd =0
error = SV - PV = 2 - 3 = -1
sum_e = sum_e + error = 4/Ki -1
MV = PID = -1(Kp) + (4/Ki -1)Ki = -1Kp + 4 - 1*Ki = -1 +4 -1 = 2
If you used a slower Ki than 1, it would smooth out the noise more and not adjust the MV so quickly:
Ki = 0.1 ;
MV = PID = -1(Kp) + (4/Ki -1)Ki = -1Kp + 4 - 1*Ki = -1 +4 -0.1 = 2.9
At steady state at target (PV = SV), sum_e * Ki should produce the steady-state MV:
PV = SV
error = SV - PV = 0
Kp * error = 0
MV = 3 = PID = 0 * Kp + Ki * sum_e
A nice way to understand the PID controller is to put units on everything and think of Kp, Ki, Kd as conversions of the process error, accumulated error*timeUnit, and rate-of-change of error/timeUnit into terms of the manipulated variable, and that the controlled system converts the controller's manipulated variable into units of output.