The problem
My code includes a module called Tests which defines the following:
broken :: SetRBT Int
broken = insertRBT 1 $ emptySetRBT (<)
I can evaluate broken in the REPL:
All> broken
RedBlackTree.RedBlackTree (_impl#==#Prelude.Eq#Prelude.Int) (_impl#==#Prelude.Eq#Prelude.Int) (_def#<#Prelude.Ord (_inst#Prelude.Ord#Prelude.Int)) (RedBlackTree.Tree RedBlackTree.Black 1 RedBlackTree.Empty RedBlackTree.Empty)
All>
I cannot, however, evaluate the RHS of broken's definition:
All> insertRBT 1 $ emptySetRBT (<)
PAKCS_Main_Exp.curry, line 3.18: Error:
Undefined type RedBlackTree.RedBlackTree
ERROR occurred during parsing!
All>
Or so I believed, until I tried attaching a type signature:
All> insertRBT 1 $ emptySetRBT (<) :: SetRBT Int
RedBlackTree.RedBlackTree (_impl#==#Prelude.Eq#Prelude.Int) (_impl#==#Prelude.Eq#Prelude.Int) (_def#<#Prelude.Ord (_inst#Prelude.Ord#Prelude.Int)) (RedBlackTree.Tree RedBlackTree.Black 1 RedBlackTree.Empty RedBlackTree.Empty)
All>
I'm fine with having to attach type signatures when needed, or more generally, to do whatever the error messages suggest I should do. But how would I know to interpret the above error message as meaning "you've got to attach a type signature"? More generally, what does that type error even mean, given that (see below) RedBlackTree is loaded?
What I am loading
Each time I start PAKCS I run :l All. That loads a module which reads, in relevant part,
module All ( module M
) where
import FiniteMap as M
import SetRBT as M
import RedBlackTree as M
import Tests as M
That idiom lets me load all the things that I need (there are others) without producing a long prompt.
If I run :modules it looks like RedBlackTree should be defined:
All> :modules
Currently loaded modules:
All (loaded from ./.curry/pakcs/All.pl)
Prelude (loaded from /home/jeff/logic/curry/install/pakcs-2.0.2/lib/.curry/pakcs/Prelude.pl)
FiniteMap (loaded from /home/jeff/logic/curry/install/pakcs-2.0.2/lib/.curry/pakcs/FiniteMap.pl)
SetRBT (loaded from /home/jeff/logic/curry/install/pakcs-2.0.2/lib/.curry/pakcs/SetRBT.pl)
RedBlackTree (loaded from /home/jeff/logic/curry/install/pakcs-2.0.2/lib/.curry/pakcs/RedBlackTree.pl)
Tests (loaded from ./.curry/pakcs/Tests.pl)
All>
You must tell the interpreter to add referenced modules.
All> :add RedBlackTree SetRBT
... some messages ...
All SetRBT RedBlackTree> insertRBT 1 $ emptySetRBT (<)
and it will work.
Related
How can one generate a random integer in Idris 1.3.3?
Example program that doesn't work:
module Random
import Effect.Random --This gets me access to the rndInt function
I run the program as follows:
idris random.idr -p effects
Trying the rndInt function in the REPL, I get the following error message:
*random> rndInt 1 10
(input):Can't infer argument m to rndInt
Please include the full source code in your answer. Thank you.
Elaborating on Alissa Tung's answer, here's the full working source code, including setting the random seed (srand) with the system time:
module Random
import Effect.Random
import Effects
import System
main : IO ()
main = do
t <- time
n <- run $ do
srand t
rndInt 1 100
putStrLn $ show n
Run with:
idris random.idr -p effects
Output:
*random> :exec main
88
*random> :exec main
96
*random> :exec main
19
I am trying to run following very simple code:
open Str
print (Str.first_chars "testing" 0)
However, it is giving following error:
$ ocaml testing2.ml
File "testing2.ml", line 2, characters 0-5:
Error: Syntax error
There are no further details in the error message.
Same error with print_endline also; or even if no print command is there. Hence, the error is in part: Str.first_chars "testing" 0
Documentation about above function from here is as follows:
val first_chars : string -> int -> string
first_chars s n returns the first n characters of s. This is the same
function as Str.string_before.
Adding ; or ;; at end of second statement does not make any difference.
What is the correct syntax for above code.
Edit:
With following code as suggested by #EvgeniiLepikhin:
open Str
let () =
print_endline (Str.first_chars "testing" 0)
Error is:
File "testing2.ml", line 1:
Error: Reference to undefined global `Str'
And with this code:
open Str;;
print_endline (Str.first_chars "testing" 0)
Error is:
File "testing2.ml", line 1:
Error: Reference to undefined global `Str'
With just print command (instead of print_endline) in above code, the error is:
File "testing2.ml", line 2, characters 0-5:
Error: Unbound value print
Note, my Ocaml version is:
$ ocaml -version
The OCaml toplevel, version 4.02.3
I think Str should be built-in, since opam is not finding it:
$ opam install Str
[ERROR] No package named Str found.
I also tried following code as suggested in comments by #glennsl:
#use "topfind"
#require "str"
print (Str.first_chars "testing" 0)
But this also give same simple syntax error.
An OCaml program is a list of definitions, which are evaluated in order. You can define values, modules, classes, exceptions, as well as types, module types, class types. But let's focus on values so far.
In OCaml, there are no statements, commands, or instructions. It is a functional programming language, where everything is an expression, and when an expression is evaluated it produces a value. The value could be bound to a variable so that it could be referenced later.
The print_endline function takes a value of type string, outputs it to the standard output channel and returns a value of type unit. Type unit has only one value called unit, which could be constructed using the () expression. For example, print_endline "hello, world" is an expression that produces this value. We can't just throw an expression in a file and hope that it will be compiled, as an expression is not a definition. The definition syntax is simple,
let <pattern> = <expr>
where is either a variable or a data constructor, which will match with the structure of the value that is produced by <expr> and possibly bind variable, that are occurring in the pattern, e.g., the following are definitions
let x = 7 * 8
let 4 = 2 * 2
let [x; y; z] = [1; 2; 3]
let (hello, world) = "hello", "world"
let () = print_endline "hello, world"
You may notice, that the result of the print_endline "hello, world" expression is not bound to any variable, but instead is matched with the unit value (), which could be seen (and indeed looks like) an empty tuple. You can write also
let x = print_endline "hello, world"
or even
let _ = print_endline "hello, world"
But it is always better to be explicit on the left-hand side of a definition in what you're expecting.
So, now the well-formed program of ours should look like this
open Str
let () =
print_endline (Str.first_chars "testing" 0)
We will use ocamlbuild to compile and run our program. The str module is not a part of the standard library so we have to tell ocamlbuild that we're going to use it. We need to create a new folder and put our program into a file named example.ml, then we can compile it using the following command
ocamlbuild -pkg str example.native --
The ocamlbuild tool will infer from the suffix native what is your goal (in this case it is to build a native code application). The -- means run the built application as soon as it is compiled. The above program will print nothing, of course, here is an example of a program that will print some greeting message, before printing the first zero characters of the testing string,
open Str
let () =
print_endline "The first 0 chars of 'testing' are:";
print_endline (Str.first_chars "testing" 0)
and here is how it works
$ ocamlbuild -package str example.native --
Finished, 4 targets (4 cached) in 00:00:00.
The first 0 chars of 'testing' are:
Also, instead of compiling your program and running the resulting application, you can interpret your the example.ml file directly, using the ocaml toplevel tool, which provides an interactive interpreter. You still need to load the str library into the toplevel, as it is not a part of the standard library which is pre-linked in it, here is the correct invocation
ocaml str.cma example.ml
You should add ;; after "open Str":
open Str;;
print (Str.first_chars "testing" 0)
Another option is to declare code block:
open Str
let () =
print (Str.first_chars "testing" 0)
I go
export PERL6LIB="/GitHub/perl6-Units/lib"
and then
echo $PERL6LIB
/GitHub/perl6-Units/lib
But when I run perl6 t/01-basic.t
use v6;
use Test;
plan 3;
lives-ok {
use Units <m>;
ok #Units::UNITS.elems > 0;
ok (0m).defined;
}
done-testing;
I still get an error
===SORRY!===
Could not find Units at line 8 in:
/Users/--me--/.perl6
/usr/local/Cellar/rakudo-star/2018.01/share/perl6/site
/usr/local/Cellar/rakudo-star/2018.01/share/perl6/vendor
/usr/local/Cellar/rakudo-star/2018.01/share/perl6
CompUnit::Repository::AbsolutePath<140707489084448>
CompUnit::Repository::NQP<140707463117264>
CompUnit::Repository::Perl5<140707463117304>
In Perl 5 I would have used print "#INC"; to see what paths are searched for the lib before the error is thrown. Using say flat $*REPO.repo-chain.map(*.loaded); either is before it loads or after it throws the exception.
Any help would be much appreciated - or maybe a hint on what to put in ~/.perl6 as I can't get a symlink to work either.
The error message itself is telling you what the library paths available are. You are failing to print them because you are expecting a run time action ( say ) to take place before a compile time error -- you could print out $*REPO at compile time, but again the exception is already showing you what you wanted.
$ PERL6LIB="/GitHub/perl6-Units/lib" perl6 -e 'BEGIN say $*REPO.repo-chain; use Foo;'
(file#/GitHub/perl6-Units/lib inst#/Users/ugexe/.perl6 inst#/Users/ugexe/.rakudobrew/moar-2018.08/install/share/perl6/site inst#/Users/ugexe/.rakudobrew/moar-2018.08/install/share/perl6/vendor inst#/Users/ugexe/.rakudobrew/moar-2018.08/install/share/perl6 ap# nqp# perl5#)
===SORRY!===
Could not find Foo at line 1 in:
/GitHub/perl6-Units/lib
/Users/ugexe/.perl6
/Users/ugexe/.rakudobrew/moar-2018.08/install/share/perl6/site
/Users/ugexe/.rakudobrew/moar-2018.08/install/share/perl6/vendor
/Users/ugexe/.rakudobrew/moar-2018.08/install/share/perl6
CompUnit::Repository::AbsolutePath<140337382425072>
CompUnit::Repository::NQP<140337350057496>
CompUnit::Repository::Perl5<140337350057536>
You can see /GitHub/perl6-Units/lib is showing up in the available paths, which is unlike your example. I'd question if your shell/env is actually setup correctly.
Is there any means to accessing (reading, writing to) files that are opened in some other source code by just passing the unit number?
Yes, that is possible (for both reading and writing). Here is a short example:
module test_mod
contains
subroutine myWrite( uFile )
implicit none
integer, intent(in) :: uFile
write(uFile, *) 'Hello world'
end subroutine
end module
program test
use test_mod
implicit none
integer :: uFile, stat
open(newunit=uFile, file='test.txt', status='replace', &
action='write', iostat=stat)
if(stat.ne.0) return
call myWrite( uFile )
close (uFile)
end program
$ cat test.txt
Hello world
External file units are globally accessible. You need not even pass the unit number, though that is a better practice than using hardcoded units. This behavior defined in Fortran 2008 Cl. 9.5.1,
3 The external unit identified by a particular value of a scalar-int-expr is the same external unit in all program
units of the program.
where they provide this sample code in note 9.14:
In the example:
SUBROUTINE A
READ (6) X
...
SUBROUTINE B
N = 6
REWIND N
the value 6 used in both program units identifies the same external unit.
When I run ANY test I get the same message. Here is an example test:
package require tcltest
namespace import -force ::tcltest::*
test foo-1.1 {save 1 in variable name foo} {} {
set foo 1
} {1}
I get the following output:
WARNING: unknown option -run: should be one of -asidefromdir, -constraints, -debug, -errfile, -file, -limitconstraints, -load, -loadfile, -match, -notfile, -outfile, -preservecore, -relateddir, -singleproc, -skip, -testdir, -tmpdir, or -verbose
I've tried multiple tests and nothing seems to work. Does anyone know how to get this working?
Update #1:
The above error was my fault, it was due to it being run in my script. However if I run the following at a command line I got no output:
[root#server1 ~]$ tcl
tcl>package require tcltest
2.3.3
tcl>namespace import -force ::tcltest::*
tcl>test foo-1.1 {save 1 in variable name foo} {expr 1+1} {2}
tcl>echo [test foo-1.1 {save 1 in variable name foo} {expr 1+1} {2}]
tcl>
How do I get it to output pass or fail?
You don't get any output from the test command itself (as long as the test passes, as in the example: if it fails, the command prints a "contents of test case" / "actual result" / "expected result" summary; see also the remark on configuration below). The test statistics are saved internally: you can use the cleanupTests command to print the Total/Passed/Skipped/Failed numbers (that command also resets the counters and does some cleanup).
(When you run runAllTests, it runs test files in child processes, intercepting the output from each file's cleanupTests and adding them up to a grand total.)
The internal statistics collected during testing is available in AFACT undocumented namespace variables like ::tcltest::numTests. If you want to work with the statistics yourself, you can access them before calling cleanupTests, e.g.
parray ::tcltest::numTests
array set myTestData [array get ::tcltest::numTests]
set passed $::tcltest::numTests(Passed)
Look at the source for tcltest in your library to see what variables are available.
The amount of output from the test command is configurable, and you can get output even when the test passes if you add p / pass to the -verbose option. This option can also let you have less output on failure, etc.
You can also create a command called ::tcltest::ReportToMaster which, if it exists, will be called by cleanupTests with the pertinent data as arguments. Doing so seems to suppress both output of statistics and at least most resetting and cleanup. (I didn't go very far in investigating that method.) Be aware that messing about with this is more likely to create trouble than solve problems, but if you are writing your own testing software based on tcltest you might still want to look at it.
Oh, and please use the newer syntax for the test command. It's more verbose, but you'll thank yourself later on if you get started with it.
Obligatory-but-fairly-useless (in this case) documentation link: tcltest