Re: How to use retro over findSplitBefore result?

Wed, 04 Dec 2013 10:42:01 -0800 

On Wednesday, 4 December 2013 at 18:26:43 UTC, Ali Çehreli wrote:

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


Thanks Ali!

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