I'm trying to interface to a classic HD44780 LCD.
I have implemented local ram to which I write the data I wish to show up on the display.
I have defined the ram in this way:
type ram_type is array (0 to (16*2)-1) of std_logic_vector(7 downto 0);
signal lcd_mem : ram_type;
I've tried initializing the ram in this way:
lcd_mem(0 to 6) <= x"45_72_72_6F_72_73_3A";
...
But I receive an error on synthesis:
Error (10515): VHDL type mismatch error at display_ber.vhd(74): ram_type type does not match string literal
Is there a way to ellegantly initialize the ram block in a similar way ?
Perhaps I should use a string type instead ?
Yes there is. Note that your definition of ram_type is an array of std_logic_vector. And x"45_72_72_6F_72_73_3A" is a hex string literal. These are not the same type, hence your error.
So, you have to put the value into an array of vectors. Such as:
lcd_mem(0 to 6) <= (0 => x"45", 1 => x"72", 2 => x"72", 3 => x"6F", 4 => x"72", 5 => x"73", 6 => x"3A");
Above answer is good. May also code as follows:
type init_type is array (0 to 6) of std_logic_vector(7 downto 0);
constant c_lcd_int : init_type:= (45,72,72,6F,72,73,3A);
lcd_mem(0 to 6) <= c_lcd_int;
Related
I am trying some things in Dafny. I want to code a simple datastructure that holds an uncompressed image in memory:
datatype image' = image(width: int, height: int, data: array<byte>)
newtype byte = b: int | 0 <= b <= 255
Actually using it:
method Main() {
var dat := [1,2,3];
var im := image(1, 3, dat);
}
datatype image' = image(width: int, height: int, data: array<byte>)
newtype byte = b: int | 0 <= b <= 255
leads Dafny to complain:
stdin.dfy(3,24): Error: incorrect type of datatype constructor argument (found seq, expected array)
1 resolution/type errors detected in stdin.dfy
I might also want to demand that the byte array is not null, and the size of the byte array is equal to width * height * 3 (to store three bytes representing the RGB value of that pixel).
What way should I enforce this? I looked into newtype, which lets you put some constraints on variables with a certain type, but this works only for numeric types.
Dafny supports both immutable sequences (which are like mathematical sequences of elements) and mutable arrays (which are, like in C and Java, pointers to elements). The error you're getting is telling you that you're calling the image constructor with a seq<byte> value where an array<byte> value is expected.
You can fix the problem by replacing your definition of dat with:
var dat := new byte[3];
dat[0], dat[1], dat[2] := 1, 2, 3;
However, the more typical thing, if you're using a datatype (which is immutable), would be to use a sequence. So, you probably want to instead change your definition of image to:
datatype image = image(width: int, height: int, data: seq<byte>)
Btw, note that Dafny allows you to name a type and one of its constructors the same, so there's no reason to name one of them with a prime (unless you want to, of course).
Another matter of style is to use a half-open interval in your definition of byte:
newtype byte = b: int | 0 <= b < 256
Since half-open intervals are prevalent in computer science, Dafny's syntax favors them. For example, for a sequence s, the expression s[52..57] denotes a subsequence of s of length 5 (that is, 57 minus 52) starting in s at index 52. One more thing, you can also leave out the type int of b if you want, since Dafny will infer it:
newtype byte = b | 0 <= b < 256
You also asked about the possibility of adding a type constraint, so that the sequence in your datatype will always be of length 3. As you discovered, you cannot do this with a newtype, because newtype (at least for now) only works with numeric types. You can (almost) use a subset type, however. This would be done as follows:
type triple = s: seq<byte> | |s| == 3
(In this example, the first vertical bar is like the one in the newtype declaration and says "such that", whereas the next two denote the length operator on sequences.) The trouble with this declaration is that types must be nonempty and Dafny isn't convinced that there are any values that satisfy the constraint of triple. Well, Dafny is not trying very hard. The plan is to add a witness clause to the type (and newtype) declaration, so that a programmer can show Dafny a value that belongs to the triple type. However, this support is waiting for some implementation changes that will allow customized initial values, so you cannot use this constraint at this time.
Not that you want it here, but Dafny would let you give a weaker constraint that admits the empty sequence:
type triple = s: seq<byte> | |s| <= 3
So, instead, if you want to talk about that an image value has a data component of length 3, then introduce a predicate:
predicate GoodImage(img: image)
{
|img.data| == 3
}
and use this predicate in specifications like pre- and postconditions.
Program safely,
Rustan
Given an integer, 98749287 say, is there some built-in/libray function, either Erlang or Elixir, for getting the size in bytes?
To clarify, the minimum number of bytes used to represent the number in binary.
Seems simple, and have written a function using the "division by base" method and then counting bits, but after some hrs of searching docs havent found anything for what would seem useful to have.
If you have an unsigned integer, you can use the following snippet:
byte_size(binary:encode_unsigned(Integer))
Example:
1> byte_size(binary:encode_unsigned(3)).
1
2> byte_size(binary:encode_unsigned(256)).
2
3> byte_size(binary:encode_unsigned(98749287)).
4
Try this expression:
Value = (... your input ...),
NumBytes = size(integer_to_binary(Value, 2) + 7) div 8.
Reference: http://www.erlang.org/doc/man/erlang.html#integer_to_binary-2
I'm trying to code something but there is happening something I don't understand.
I get some values from a database and loop over them and change some of them if needed.
This is what I'm trying to do:
if qryGeneral.fieldbyname('B_PRIJS').IsNull or
qryGeneral.fieldbyname('B_PRIJS').Value = 0 then
begin
if (qryGeneral.fieldbyname('V_PRIJS').Value <> 0) or
(qryGeneral.fieldbyname('V_PRIJSEXCL').Value <> 0) then
//make some calculations and save data
end;
B_PRIJS is a float, null type in a SQL Server DB. When I set a breakpoint and I hover .Value it shows 0,11. When I hover IsNull it shows False, so far so good.
Now I would expect it would NOT enter the if-structure, because it is not null and not equal to 0, but it does enter the if-structure.
I don't understand why, I always coded like this.
When I select qryGeneral.fieldbyname('B_PRIJS').Value = 0 while still being in debug mode, I get a message "Expression illegal in evaluator".
I tried replacing Value into AsFloat or changing 0 into 0.0 but it doesn't work.
What am I doing wrong or not understanding here?
Delphi's operator precedence rules mean that your expression is evaluated like this:
if (qryGeneral.fieldbyname('B_PRIJS').IsNull or qryGeneral.fieldbyname('B_PRIJS').Value)
= 0 then
Put parentheses around your = expression just like you have around you <> expressions, and you should get closer to the results you expect. However, the Value property is a Variant. When comparing a Variant to an Integer, the = operator will cause the Variant to be converted to an Integer. Delphi's variant-type-conversion rules show that a Variant holding a real value will be rounded to the nearest integer when the target type is an integer, so your 0.11 value will be rounded to zero. Consider comparing to 0.0 instead.
I have many text files of this format
....
<snip>
'FOP' 0.19 1 24 1 25 7 8 /
'FOP' 0.18 1 24 1 25 9 11 /
/
TURX
560231
300244
70029
200250
645257
800191
900333
600334
770291
300335
220287
110262 /
SUBTRACT
'TURX' 'TURY'/
</snip>
......
where the portions I snipped off contain other various data in various formats. The file format is inconsistent (machine generated), the only thing one is assured of is the keyword TURX which may appear more than once. If it appears alone on one line, then the next few lines will contain numbers that I need to fetch into an array. The last number will have a space then a forward slash (/). I can then use this array in other operations afterwards.
How do I "search" or parse a file of unknown format in fortran, and how do I get a loop to fetch the rest of the data, please? I am really new to this and I HAVE to use fortran. Thanks.
Fortran 95 / 2003 have a lot of string and file handling features that make this easier.
For example, this code fragment to process a file of unknown length:
use iso_fortran_env
character (len=100) :: line
integer :: ReadCode
ReadLoop: do
read (75, '(A)', iostat=ReadCode ) line
if ( ReadCode /= 0 ) then
if ( ReadCode == iostat_end ) then
exit ReadLoop
else
write ( *, '( / "Error reading file: ", I0 )' ) ReadCode
stop
end if
end if
! code to process the line ....
end do ReadLoop
Then the "process the line" code can contain several sections depending on a logical variable "Have_TURX". If Have_TRUX is false you are "seeking" ... test whether the line contains "TURX". You could use a plain "==" if TURX is always at the start of the string, or for more generality you could use the intrinsic function "index" to test whether the string "line" contains TURX.
Once the program is in the mode Have_TRUX is true, then you use "internal I/O" to read the numeric value from the string. Since the integers have varying lengths and are left-justified, the easiest way is to use "list-directed I/O": combining these:
read (line, *) integer_variable
Then you could use the intrinsic function "index" again to test whether the string also contains a slash, in which case you change Have_TRUX to false and end reading mode.
If you need to put the numbers into an array, it might be necessary to read the file twice, or to backspace the file, because you will have to allocate the array, and you can't do that until you know the size of the array. Or you could pop the numbers into a linked list, then when you hit the slash allocate the array and fill it from the linked list. Or if there is a known maximum number of values you could use a temporary array, then transfer the numbers to an allocatable output array. This is assuming that you want the output argument of the subroutine be an allocatable array of the correct length, and the it returns one group of numbers per call:
integer, dimension (:), allocatable, intent (out) :: numbers
allocate (numbers (1: HowMany) )
P.S. There is a brief summary of the language features at http://en.wikipedia.org/wiki/Fortran_95_language_features and the gfortran manual has a summary of the intrinsic procedures, from which you can see what built in functions are available for string handling.
I'll give you a nudge in the right direction so that you can finish your project.
Some basics:
Do/While as you'll need some sort of loop
structure to loop through the file
and then over the numbers. There's
no for loop in Fortran, so use this
type.
Read
to read the strings.
To start you need something like this:
program readlines
implicit none
character (len=30) :: rdline
integer,dimension(1000) :: array
! This sets up a character array with 30 positions and an integer array with 1000
!
open(18,file='fileread.txt')
do
read(18,*) rdline
if (trim(rdline).eq.'TURX') exit !loop until the trimmed off portion matches TURX
end do
See this thread for way to turn your strings into integers.
Final edit: Looks like MSB has got most of what I just found out. The iostat argument of the read is the key to it. See this site for a sample program.
Here was my final way around it.
PROGRAM fetchnumbers
implicit none
character (len=50) ::line, numdata
logical ::is_numeric
integer ::I,iost,iost2,counter=0,number
integer, parameter :: long = selected_int_kind(10)
integer, dimension(1000)::numbers !Can the number of numbers be up to 1000?
open(20,file='inputfile.txt') !assuming file is in the same location as program
ReadLoop: do
read(20,*,iostat=iost) line !read data line by line
if (iost .LT. 0) exit !end of file reached before TURX was found
if (len_trim(line)==0) cycle ReadLoop !ignore empty lines
if (index(line, 'TURX').EQ.1) then !prepare to begin capturing
GetNumbers: do
read(20, *,iostat=iost2)numdata !read in the numbers one by one
if (.NOT.is_numeric(numdata)) exit !no more numbers to read
if (iost2 .LT. 0) exit !end of file reached while fetching numbers
read (numdata,*) number !read string value into a number
counter = counter + 1
Storeloop: do I =1,counter
if (I<counter) cycle StoreLoop
numbers(counter)=number !storing data into array
end do StoreLoop
end do GetNumbers
end if
end do ReadLoop
write(*,*) "Numbers are:"
do I=1,counter
write(*,'(I14)') numbers(I)
end do
END PROGRAM fetchnumbers
FUNCTION is_numeric(string)
IMPLICIT NONE
CHARACTER(len=*), INTENT(IN) :: string
LOGICAL :: is_numeric
REAL :: x
INTEGER :: e
is_numeric = .FALSE.
READ(string,*,IOSTAT=e) x
IF (e == 0) is_numeric = .TRUE.
END FUNCTION is_numeric
Why does StrToInt('X5') returns 5 in Delphi? Is X some scientific notation or something like it? Are there some other chars which will be converted to Integer as well?
Not knowing Delphi, I'd wager that the "X" causes the function to assume the value is hexidecimal. Since 0x5 == 5, it appears to be working. Try X10 and see if you get back 16.
In Delphi, hexadecimal values are marked with $ prefix:
a := $10; // => a = 16
But since in some other languages (e.g. C) X is used for marking hexadecimal values, StrToInt function supports both $ and X prefixes, so both of the codes below return 16:
a := StrToInt('x10'); // => a = 16
a := StrToInt('$10'); // => a = 16
It's hex notation. Try XF to see it return 15.
Probably hexadecimal notation.
The X indicates that the number that follows is hexadecimal (0-9 + A-F).