Re: How to use retro over findSplitBefore result?

[Ali Çehreli]

On 12/04/2013 09:43 AM, MrSmith wrote:
I am trying to compile following code
import std.algorithm : findSplitBefore;
import std.range : retro;
import std.array : array;

// returns file path where name has suffix and prefix
string withSuffixPrefix(string filePath, string prefix, string suffix)
{
     auto splitted = filePath.retro.findSplitBefore("/");

     return cast(string)splitted[1].retro.array
         ~ prefix
         ~ cast(string)splitted[0].retro.array //Fails!
         ~ suffix;
}

With following error:
build.d(56): Error: template std.range.retro does not match any function
template declaration. Candidates are:
/phobos/std/range.d(1455):   std.range.retro(Range)(Range r) if
(isBidirectionalRange!(Unqual!Range))
build.d(56): Error: template std.range.retro(Range)(Range r) if
(isBidirectionalRange!(Unqual!Range)) cannot deduce template function
from argument types !()(Result)

Seems like i need to somehow convert splitted[0] to Bidirectional range.

This function will be used like this:
assert(withSuffixPrefix("/some/random/path/to/file", "pref-", ".fl") ==
"/some/random/path/to/pref-file.fl");

The main reason is that the ranges that findSplitBefore produces are not 
BidirectionalRanges. retro requires a BidirectionalRange and for that 
reason splitted[0].retro fails. The following solution inserts an .array 
to produce a BidirectionalRange.

However, I don't see any reason why findSplitBefore could not produce 
BidirectionalRanges when it operated on a BidirectionalRange to begin with.

Just to stay with your algorithm, you can also use std.conv.text (as 
well as std.conv.to!string, which Jesse Phillips recomended):

import std.algorithm : findSplitBefore;
import std.range;
import std.array : array;
import std.stdio;
import std.conv;

// returns file path where name has suffix and prefix
string withSuffixPrefix(string filePath, string prefix, string suffix)
{
    auto splitted = filePath.retro.findSplitBefore("/");

    static assert(!isBidirectionalRange!(typeof(splitted[0])));

    return splitted[1].retro.text
        ~ prefix
        ~ splitted[0].array.retro.text
        ~ suffix;
}

void main()
{
    writeln(withSuffixPrefix("/some/random/path/to/file", "pref-", ".fl"));
}

Alternatively, you can use std.path:

import std.path;
import std.string;

string withSuffixPrefix(string filePath, string prefix, string suffix)
{
    return format("%s/%s%s%s",
                  filePath.dirName, prefix, filePath.baseName, suffix);
}

void main()
{
    assert(withSuffixPrefix("/some/random/path/to/file", "pref-", ".fl") ==
           "/some/random/path/to/pref-file.fl");
}

Ali