I would like to perform double substitution.
When printing:
def y = "\${x}"
def x = "world"
def z = "Hello ${y}"
println z
It prints:
Hello ${x}
When I would like it to print Hello World, I tried performing a double evaluation ${${}}, casting it to org.codehaus.groovy.runtime.GStringImpl, and a desperate ${y.toStrin()}
Edit:
To be more clear I mean this, but in Groovy:
https://unix.stackexchange.com/questions/68042/double-and-triple-substitution-in-bash-and-zsh
https://unix.stackexchange.com/questions/68035/foo-and-zsh
(Why I am doing this?: Because we have some text files that we need evaluate with groovy variables; the variables are many and in different part of the code are different, therefore I would like to have a solution working across all cases, not to have to bind each time each variable, not adding many lines of code)
So with what you have you're escaping the $ so it is just interpreted as a string.
For what you are looking to do I would look into Groovys's templating engines:
http://docs.groovy-lang.org/docs/next/html/documentation/template-engines.html
After reading your comment I played around with a few ideas and came up with this contrived answer, which is also probably not quite what you are looking for:
import groovy.lang.GroovyShell
class test{
String x = "world"
String y = "\${x}"
void function(){
GroovyShell shell = new GroovyShell();
Closure c = shell.evaluate("""{->"Hello $y"}""")
c.delegate = this
c.resolveStrategry = Closure.DELEGATE_FIRST
String z = c.call()
println z
}
}
new test().function()
But it was the closest thing I could come up with, and may lead you to something...
If I understand right, you are reading y from somewhere else. So you want to evaluate y as a GString after y and then x have been loaded. groovy.util.Eval will do this for simple cases. In this case, you have just one binding variable: x.
def y = '${x}'
def x = 'world'
def script = "Hello ${y}"
def z = Eval.me('x', x, '"' + script + '".toString()') // create a new GString expression from the string value of "script" and evaluate it to interpolate the value of "x"
println z
Related
I have a sequence of values that I know at compile-time, for example: const x: seq[string] = #["s1", "s2", "s3"]
I want to loop over that seq in a manner that keeps the variable a static string instead of a string as I intend to use these strings with macros later.
I can iterate on objects in such a manner using the fieldPairs iterator, but how can I do the same with just a seq?
A normal loop such as
for s in x:
echo s is static string
does not work, as s will be a string, which is not what I need.
The folks over at the nim forum were very helpful (here the thread).
The solution appears to be writing your own macro to do this. 2 solutions I managed to make work for me were from the users mratsim and a specialized version from hlaaftana
Hlaaftana's version:
This one unrolls the loop over the various values in the sequence. By that I mean, that the "iterating variable s" changes its value and is always the value of one of the entries of that compile-time seq x (or in this example a). In that way it functions basically like a normal for-in loop.
import macros
macro unrollSeq(x: static seq[string], name, body: untyped) =
result = newStmtList()
for a in x:
result.add(newBlockStmt(newStmtList(
newConstStmt(name, newLit(a)),
copy body
)))
const a = #["la", "le", "li", "lo", "lu"]
unrollSeq(a, s):
echo s is static
echo s
mratsim's version:
This one doesn't unroll a loop over the values, but over a range of indices.
You basically tell the staticFor macro over what range of values you want an unrolled for loop and it generates that for you. You can access the individual entries in the seq then with that index.
import std/macros
proc replaceNodes(ast: NimNode, what: NimNode, by: NimNode): NimNode =
# Replace "what" ident node by "by"
proc inspect(node: NimNode): NimNode =
case node.kind:
of {nnkIdent, nnkSym}:
if node.eqIdent(what):
return by
return node
of nnkEmpty:
return node
of nnkLiterals:
return node
else:
var rTree = node.kind.newTree()
for child in node:
rTree.add inspect(child)
return rTree
result = inspect(ast)
macro staticFor*(idx: untyped{nkIdent}, start, stopEx: static int, body: untyped): untyped =
result = newStmtList()
for i in start .. stopEx: # Slight modification here to make indexing behave more in line with the rest of nim-lang
result.add nnkBlockStmt.newTree(
ident("unrolledIter_" & $idx & $i),
body.replaceNodes(idx, newLit i)
)
staticFor(index, x.low, x.high):
echo index
echo x[index] is static string
Elegantbeefs version
Similar to Hlaaftana's version this unrolls the loop itself and provides you a value, not an index.
import std/[macros, typetraits]
proc replaceAll(body, name, wth: NimNode) =
for i, x in body:
if x.kind == nnkIdent and name.eqIdent x:
body[i] = wth
else:
x.replaceAll(name, wth)
template unrolledFor*(nameP, toUnroll, bodyP: untyped): untyped =
mixin
getType,
newTree,
NimNodeKind,
`[]`,
add,
newIdentDefs,
newEmptyNode,
newStmtList,
newLit,
replaceAll,
copyNimTree
macro myInnerMacro(name, body: untyped) {.gensym.} =
let typ = getType(typeof(toUnroll))
result = nnkBlockStmt.newTree(newEmptyNode(), newStmtList())
result[^1].add nnkVarSection.newTree(newIdentDefs(name, typ[^1]))
for x in toUnroll:
let myBody = body.copyNimTree()
myBody.replaceAll(name, newLit(x))
result[^1].add myBody
myInnerMacro(nameP, bodyP)
const x = #["la", "le", "Li"]
unrolledFor(value, x):
echo value is static
echo value
All of them are valid approaches.
I working on a language similar to ruby called gaiman and I'm using PEG.js to generate the parser.
Do you know if there is a way to implement heredocs with proper indentation?
xxx = <<<END
hello
world
END
the output should be:
"hello
world"
I need this because this code doesn't look very nice:
def foo(arg) {
if arg == "here" then
return <<<END
xxx
xxx
END
end
end
this is a function where the user wants to return:
"xxx
xxx"
I would prefer the code to look like this:
def foo(arg) {
if arg == "here" then
return <<<END
xxx
xxx
END
end
end
If I trim all the lines user will not be able to use a string with leading spaces when he wants. Does anyone know if PEG.js allows this?
I don't have any code yet for heredocs, just want to be sure if something that I want is possible.
EDIT:
So I've tried to implement heredocs and the problem is that PEG doesn't allow back-references.
heredoc = "<<<" marker:[\w]+ "\n" text:[\s\S]+ marker {
return text.join('');
}
It says that the marker is not defined. As for trimming I think I can use location() function
I don't think that's a reasonable expectation for a parser generator; few if any would be equal to the challenge.
For a start, recognising the here-string syntax is inherently context-sensitive, since the end-delimiter must be a precise copy of the delimiter provided after the <<< token. So you would need a custom lexical analyser, and that means that you need a parser generator which allows you to use a custom lexical analyser. (So a parser generator which assumes you want a scannerless parser might not be the optimal choice.)
Recognising the end of the here-string token shouldn't be too difficult, although you can't do it with a single regular expression. My approach would be to use a custom scanning function which breaks the here-string into a series of lines, concatenating them as it goes until it reaches a line containing only the end-delimiter.
Once you've recognised the text of the literal, all you need to normalise the spaces in the way you want is the column number at which the <<< starts. With that, you can trim each line in the string literal. So you only need a lexical scanner which accurately reports token position. Trimming wouldn't normally be done inside the generated lexical scanner; rather, it would be the associated semantic action. (Equally, it could be a semantic action in the grammar. But it's always going to be code that you write.)
When you trim the literal, you'll need to deal with the cases in which it is impossible, because the user has not respected the indentation requirement. And you'll need to do something with tab characters; getting those right probably means that you'll want a lexical scanner which computes visible column positions rather than character offsets.
I don't know if peg.js corresponds with those requirements, since I don't use it. (I did look at the documentation, and failed to see any indication as to how you might incorporate a custom scanner function. But that doesn't mean there isn't a way to do it.) I hope that the discussion above at least lets you check the detailed documentation for the parser generator you want to use, and otherwise find a different parser generator which will work for you in this use case.
Here is the implementation of heredocs in Peggy successor to PEG.js that is not maintained anymore. This code was based on the GitHub issue.
heredoc = "<<<" begin:marker "\n" text:($any_char+ "\n")+ _ end:marker (
&{ return begin === end; }
/ '' { error(`Expected matched marker "${begin}", but marker "${end}" was found`); }
) {
const loc = location();
const min = loc.start.column - 1;
const re = new RegExp(`\\s{${min}}`);
return text.map(line => {
return line[0].replace(re, '');
}).join('\n');
}
any_char = (!"\n" .)
marker_char = (!" " !"\n" .)
marker "Marker" = $marker_char+
_ "whitespace"
= [ \t\n\r]* { return []; }
EDIT: above didn't work with another piece of code after heredoc, here is better grammar:
{ let heredoc_begin = null; }
heredoc = "<<<" beginMarker "\n" text:content endMarker {
const loc = location();
const min = loc.start.column - 1;
const re = new RegExp(`^\\s{${min}}`, 'mg');
return {
type: 'Literal',
value: text.replace(re, '')
};
}
__ = (!"\n" !" " .)
marker 'Marker' = $__+
beginMarker = m:marker { heredoc_begin = m; }
endMarker = "\n" " "* end:marker &{ return heredoc_begin === end; }
content = $(!endMarker .)*
I'm creating a simple matrix like follows:
for x = 0, 50 do
current_level[x] = {}
for y = 0, 50 do
current_level[x][y] = grabTile();
end
end
After that i try to read it, but somehow the x is now a object not a number, while y seems perfectly fine!
How i try reading it:
for x,value in pairs(self.map) do
if value == ni then print("none"); return;end;
for y,object in pairs(value) do
if object == ni then print("none"); return;end;
object:render(x,y); -- Here x is an object
end
end
I'm new to working with lua, so i might be doing something obvious terribly wrong.
How would i make this work?
What i get for x is something like: table: 0x07c8d530
This value stays the same along the complete iteration
object:render(x,y); -- Here x is an object
This line is using colon syntax. It is a syntactic sugar for object.render(object,x,y) call.
So your render() function must have the first self argument declared either explicitly as function render(self, x, y) or implicitly with another syntactic sugar for definition: function object:render(x,y).
Unrelated hint. The first loop will be faster/smaller if transformed to:
for x = 0, 50 do
local row = {}
for y = 0, 50 do
row[y] = grabTile();
end
current_level[x] = row
end
i am new with f# , will be great if some 1 can help , nearly half a day gone solving this problem Thank you
module Certificate =
type T = {
Id: int
IsECert: bool
IsPrintCert: bool
CertifiedBy: string
Categories: Category.T list
}
let createPending now toZonedDateTime toBeCertifiedByName (job: Models.Job.T) (certificateType: Models.CertificateType.T) (pendingCertificate: Models.PendingCertificate.T) visualization (categories: Category.T list) =
let forCompletion = Models.PendingCertificate.getCertificateForCompletion pendingCertificate
{
Id = forCompletion.Id |> CertificateId.toInt
IsECert = Models.PendingCertificate.isECertificate pendingCertificate
IsPrintCert = Models.PendingCertificate.isPrintCertificate pendingCertificate
CertifiedBy = toBeCertifiedByName
Categories = categories}
i am getting an error in "Incomplete structured construct at or before this point"
Your formatting is all off. I will assume here that this is just a result of posting to StackOverflow, and your actual code is well indented.
The error comes from the definition of createPending: this function does not have a result. All its body consists of defining a forCompletion value, but there is nothing after it. Here's a simpler example that has the same problem:
let f x =
let y = 5
This function will produce the same error, because it also doesn't have a result. In F#, every function has to return something. The body cannot contain only definitions of helper functions or values. For example, I could fix my broken function above like this:
let f x =
let y = 5
x + y
This function first defines a helper value y, then adds it to its argument x, and returns the result.
> f 2
> 7
>
> f 0
> 5
How exactly you need to fix your function depends on what exactly you want it to mean. I can't help you here, because you haven't provided that information.
I am starting to learn Lua from Programming in Lua (2nd edition)
I didn't understand the following in the book. Its very vaguely explained.
a.) w={x=0,y=0,label="console"}
b.) x={math.sin(0),math.sin(1),math.sin(2)}
c.) w[1]="another field"
d.) x.f=w
e.) print (w["x"])
f.) print (w[1])
g.) print x.f[1]
When I do print(w[1]) after a.), why doesn't it print x=0
What does c.) do?
What is the difference between e.) and print (w.x)?
What is the role of b.) and g.)?
You have to realize that this:
t = {3, 4, "eggplant"}
is the same as this:
t = {}
t[1] = 3
t[2] = 4
t[3] = "eggplant"
And that this:
t = {x = 0, y = 2}
is the same as this:
t = {}
t["x"] = 0
t["y"] = 2
Or this:
t = {}
t.x = 0
t.y = 2
In Lua, tables are not just lists, they are associative arrays.
When you print w[1], then what really matters is line c.) In fact, w[1] is not defined at all until line c.).
There is no difference between e.) and print (w.x).
b.) creates a new table named x which is separate from w.
d.) places a reference to w inside of x. (NOTE: It does not actually make a copy of w, just a reference. If you've ever worked with pointers, it's similar.)
g.) Can be broken up in two parts. First we get x.f which is just another way to refer to w because of line d.). Then we look up the first element of that table, which is "another field" because of line c.)
There's another way of creating keys in in-line table declarations.
x = {["1st key has spaces!"] = 1}
The advantage here is that you can have keys with spaces and any extended ASCII character.
In fact, a key can be literally anything, even an instanced object.
function Example()
--example function
end
x = {[Example] = "A function."}
Any variable or value or data can go into the square brackets to work as a key. The same goes with the value.
Practically, this can replace features like the in keyword in python, as you can index the table by values to check if they are there.
Getting a value at an undefined part of the table will not cause an error. It will just give you nil. The same goes for using undefined variables.
local w = {
--[1] = "another field"; -- will be set this value
--["1"] = nil; -- not save to this place, different with some other language
x = 0;
y = 0;
label = "console";
}
local x = {
math.sin(0);
math.sin(1);
math.sin(2);
}
w[1] = "another field" --
x.f = w
print (w["x"])
-- because x.f = w
-- x.f and w point one talbe address
-- so value of (x.f)[1] and w[1] and x.f[1] is equal
print (w[1])
print ((x.f)[1])
print (x.f[1])
-- print (x.f)[1] this not follows lua syntax
-- only a function's has one param and type of is a string
-- you can use print "xxxx"
-- so you print x.f[1] will occuur error
-- in table you can use any lua internal type 's value to be a key
-- just like
local t_key = {v=123}
local f_key = function () print("f123") end
local t = {}
t[t_key] = 1
t[f_key] = 2
-- then t' key actualy like use t_key/f_key 's handle
-- when you user t[{}] = 123,
-- value 123 related to this no name table {} 's handle