Re: How to instantiate a map with multiple functions
On Saturday, 26 December 2015 at 19:30:24 UTC, karthikeyan wrote: How to instantiate a map with multiple functions. I looked into the docs at http://dlang.org/phobos/std_algorithm_iteration.html#map. They contain a string which I suppose is a mixin and when I change "a" to some other name it results in an error for me. Are there any ways to use lambda functions directly instead of strings and any explanation of the strings used in the map example and why a is used will be helpful. I tried reading the source https://github.com/D-Programming-Language/phobos/blob/master/std/algorithm/iteration.d#L520 .Some hint that "a" should be used at https://github.com/D-Programming-Language/phobos/blob/master/std/functional.d#L101 but how do I change that since map doesn't allow me any params to specify the parameter name. Also how can I map an array of tuples with two or more elements with a function of two or more params like unpack the tuple into a function like that. I am D beginner so any will insights will be very helpful for me. I am using dmd version 2.069 on Linux Mint 15 - 64bit You should be able to just use any function (including lambdas) as a template argument to map. The string version is from before the more concise "=>" lambda syntax was developed, and generally isn't what you want to use nowadays.
Re: How to check if JSONValue of type object has a key?
On Tuesday, 6 October 2015 at 20:44:30 UTC, via
Digitalmars-d-learn wrote:
On Tue, Oct 06, 2015 at 08:28:46PM +, Borislav Kosharov via
Digitalmars-d-learn wrote:
JSONValue root = parseJSON(text);
if(root["key"].isNull == false) {
try
if("key" in root) {
// it is there
} else {
// it is not there
}
you can also do
if("key" !in root) {}
Additionally, just like associative arrays, if you need to access
the value, you can get a pointer to it with the in operator (and
if the key doesn't exist, it will return a null pointer).
const(JSONValue)* p = "key" in root;
if (p)
{
// key exists, do something with p or *p
}
else
{
// key does not exist
}
Re: Checking that a template parameter is an enum
On Thursday, 1 October 2015 at 00:04:18 UTC, Nordlöw wrote:
How do I check that a template parameter is a CT-value or an
enum symbol?
I want this to restrict the following template:
/** Returns: true iff all values $(D V) are the same. */
template allSame(V...) // TODO restrict to values only
{
static if (V.length <= 1)
enum bool allSame = true;
else
enum bool allSame = V[0] == V[1] && allSame!(V[1..$]);
}
unittest
{
static assert(!allSame!(41, 42));
static assert(allSame!(42, 42, 42));
}
std.traits to the rescue!
http://dlang.org/phobos/std_traits.html#isExpressions
Using isExpressions!V as a template constraint looks like the
behavior you're looking for.
Re: Trouble with template parameter matching
On Sunday, 2 August 2015 at 08:08:05 UTC, tcak wrote:
[code]
void func1(N)( const N name )
if( is(N: string) || is(N: char[]) )
{
func2( name );
}
[...]
This seems like the reasonable behavior to me. Perhaps you
should use Unqual?
http://dlang.org/phobos/std_traits.html#Unqual
Re: Are Lua tables possible to do with D?
On Thursday, 16 July 2015 at 06:48:12 UTC, Robert M. Münch wrote: Hi, do you think it's possible to implemented something like Lua Tables (a hashed heterogeneous associative array) in D? I know that Lua is dynamic and interpreted, hence it's a lot simpler to do than with a compiled language but I'm wondering if we could express such a generic data-structure in D. An associative array of Variant[string] ought to do the job well enough. http://dlang.org/phobos/std_variant.html
