Maybe I'm missing something obvious, but I how can I view the expression tree for this query:
from word in "The quick brown fox jumps over the lazy dog".Split()
orderby word.Length
select word
using LINQPad?
You can view the objects that make up the expression tree as follows:
(from word in "The quick brown fox jumps over the lazy dog".Split().AsQueryable()
orderby word.Length
select word).Expression
from word in "The quick brown fox jumps over the lazy dog".Split().AsQueryable()
orderby word.Length
select word
Then press the λ button next to Results.
EDIT: This will let you see the lambda expression, but I can't seem to find the expression tree in the sense of the Expression Tree Visualizer. Allegedly LINQPad has (had?) one, but I'm not finding it either.
You can also use the .Dump() method available on all objects inside LinqPAD to dump an expression tree into the results window.
Related
In practice I prefer to write R codes with Notepad++ and NppToR, where you can use the default shortcut keys to achieve the following functions:
F8: Pass line or selection
Shift+F8: Pass to point of cursor (from the very beginning)
Ctrl +F8: Pass entire file at once
Ctrl+Shift+F8: Pass by source (i.e., source("C:/Users/lenovo/Desktop/yourRcode.r"))
It is said that Julia is as simple as R or Python, but much faster than the latter two, almost as fast as C or Fortran. Thus, I try to use Julia to write codes.
According to julia-NotepadPlusPlus, we can use Julia with Notepad++ and AutoHotkey, where one can achieve the following goals:
Win-F12 -> Start Julia
Left_Shift-Enter -> Evaluate current line
Right_Shift-Enter -> Evaluate selected block
I want to write a NppToJulia.ahk file to link Notepad++ and Julia, achieving the functions as the R-NpptoR-Notepad++ way:
F8: Pass line or selection
Shift+F8: Pass to point of cursor (from the very beginning)
Ctrl +F8: Pass entire file at once
Ctrl+Shift+F8: Pass by source (i.e., include("C:/Users/lenovo/Desktop/yourJuliaCode.jl"))
As I know nothing about AutoHotkey, can anyone give me some hints?
I understand when and how to use => in Ada, specifically when using the keyword 'others', but I am not sure of its proper name nor how and why it was created. The history and development of Ada is very interesting to me and I would appreciate anyone's insight on this.
=> is called arrow. It is used with any form of parameter, not only with the parameter 'others'.
Section 6.4 of the Ada Reference Manual states:
parameter_association ::= [formal_parameter_selector_name =>]
explicit_actual_parameter
explicit_actual_parameter ::= expression | variable_name
A parameter_association is named or positional according to whether or
not the formal_parameter_selector_name is specified. Any positional
associations shall precede any named associations. Named associations
are not allowed if the prefix in a subprogram call is an
attribute_reference.
Similarly, array aggregates are described in section 4.3.3
array_aggregate ::= positional_array_aggregate |
named_array_aggregate
positional_array_aggregate ::=
(expression, expression {, expression}) | (expression {, expression}, others => expression) | (expression {, expression},
others => <>)
named_array_aggregate ::=
(array_component_association {, array_component_association})
array_component_association ::=
discrete_choice_list => expression | discrete_choice_list => <>
The arrow is used to associate an array index with a specific value or to associate a formal parameter name of a subprogram with the actual parameter.
Stack Overflow isn’t really the place for this kind of question, which is why it's received at least one close vote.
That said, "arrow" has been present in the language since its first version; see ARM83 2.2. See also the Ada 83 Rationale; section 3.5 seems to be the first place where it’s actually used, though not by name.
As a complement to Jim's answer, on the usage/intuitiveness side: the arrow X => A means in various places of the Ada syntax: value A goes to place X. It is very practical, for instance, to fill an array with an arbitrary cell order. See slide 8 of this presentation for an application with large arrays. Needless to say that the absence of the arrow notation would lead to a heap of bugs in such a case. Sometimes it is just useful for making the associations more readable. You can see it here in action for designing a game level.
I have a Java-side class with essential behaviour like:
declare Datum
description: String
broader: List <Datum>
narrower: List <Datum>
end
I want to write
query rootDatumsFor(Datum datum)
that provides a list of the root datums - that is, work "up" the broader property and return a list of each datum that has an empty broader list.
I am getting totally confused how to write this - mainly because of the negation involved.
I think I want something like
query rootDatumsFor( Datum datum )
not Datum() from $datum.broader
or
rootDatumsFor( $datum.broader )
end
But I am getting confused on both parts. If there are no broader terms, which the not should detect, how do I "return" the current value of $datum? I feel each part wants a $result and I want to do a $result: $datum but that isn't valid.
And I'm not certain how to do the recursion. Should I have rootDatumsFor(datum, result) and do it via binding?
I've seen examples that do things likes Datum( this == $datum) but that doesn't seem to be accepted when I try it.
Any assistance, whilst I keep re-reading the docn to find a little clue how to proceed, would be much appreciated.
To find all Datum facts with an empty broaderlist, all you have to do is
query rootDatumsFor( Datum $datum )
$datum: Datum( broader.size() == 0 )
end
I have this predicate that I can't seem to get to work.
The predicate should be used the following way: You give the predicate a list of things (KnowledgeList), and an uninstantiated variable (ExtractedList).
The predicate then should proceed filling ExtractedList.
To fill ExtractedList it iterates over the items of KnowledgeList,
builds a new list of extracted things, and appends this list to ExtractedList.
I know I should probably use recursion to solve this, but I feel stumped at the moment.
extractedKnowledge(KnowledgeList, ExtractedList) :-
list(KnowledgeList),
ExtractedList = [],
length(KnowledgeList,ListLength),
for(X,1,ListLength),
nth(X,KnowledgeList,ListElement),
...?
Since you unify ExtractedList which [], it will always be empty. You should indeed use recursion. Here's a skeletal recursive program to get you started:
% base case: we can only extract 0 items from 0 items
extracted_knowledge([],[]).
% recursive case
extracted_knowledge([Item|Knowledge], Extracted) :-
extracted_knowledge(Knowledge, Extracted0),
% build Extracted from Extracted0 by adding Item,
% if it needs to be extracted
My Taglist in a C code:
macro
|| MIN_LEN
|| MAX_ITERATIONS
||- typedef
|| cell
|| source_cell
||- variable
|| len_given
Taglist elements (domain):
A = {MIN_LEN, MAX_ITERATIONS, cell, source_cell, len_given}
Code snippets (codomain):
B = {"code_MIN_LEN", "code_MAX_ITERATIONS", ..., "code_len_given"}
Goal: to have bijection between the sets A and B.
Example: I want to remove any element in A, such as the MIN_LEN, from A and B by removing either its element in A or B.
Question: Is there a way to quarantee a bijection between A and B so that a change either in A or in B results in a change in the other set?
I strongly doubt you can do that. The taglist plugin uses ctags to collect the symbols in your code and display them in a lateral split. The lateral split contains readonly information (if you try to work on that window, vim tells you that modifiable is off for that buffer).
What you want to achieve would imply quite complex parsing of the source code you are modifying. Even a simple task like automatic renaming (assuming you modify a function name entry in the taglist buffer and all the instances in your source are updated) requires pretty complex parsing, which is beyond the ctags features or taglist itself. Deleting and keeping everything in sync with a bijective relationship is even more complex. Suppose you have a printf line where you use a macro you want to remove. What should happen to that line? should the whole line disappear, or just the macro (in that case, the line will probably be syntactically incorrect.
taglist is a nice plugin for browsing your code, but it's unsuited for automatic refactoring (which is what you want to achieve).
Edit: as for the computational complexity, well, the worst case scenario is that you have to scout the whole document at every keystroke, looking for new occurrence of labels that could be integrated, so in this sense you could say it's O(n) at each keystroke. This is of course overkill and the worst method to implement it. I am not aware of the computational complexity of the syntax highlight in vim, (which would be useful to extract tags as well, via proper tokenization), but I would estimate it very low, and very limited in the amount of parsed data (you are unlikely to have large constructs to parse to extract the token and understand its context). In any case, this is not how taglist works. Taglist runs ctags at every vim invocation, it does not parse the document live while you type. This is however done by Eclipse, XCode and KDevelop for example, which also provide tools for automatic or semiautomatic refactoring, and can eventually integrate vim as an editor. If you need these features, you are definitely using the wrong tool.