On 9/27/20 11:54 AM, tastyminerals wrote:
> I have a collection of functions that all have the same input, a string.
> The output however is different and depending on what the function does
> it can be ulong, double or bool.
The following approach overcomes the different return type issue by
creating delegates that take string and return string:
auto numberOfPunctChars(string text) {
return 42;
}
auto ratioOfDigitsToChars(string text) {
return 1.5;
}
auto hasUnbalancedParens(string text) {
return true;
}
struct FeatureSet {
alias TakesString = string delegate(string);
TakesString[] features;
void register(Func)(Func func) {
// Here, we convert from a function returning any type
// to a delegate returning string:
features ~= (string s) {
import std.conv : text;
return func(s).text;
};
}
// Here, we apply all feature delegates and put the outputs
// into the provided output range.
void apply(O)(ref O outputRange, string s) {
import std.format : formattedWrite;
import std.algorithm : map;
outputRange.formattedWrite!"%-(%s\n%|%)"(features.map!(f => f(s)));
}
}
void main() {
auto featureSet = FeatureSet();
featureSet.register(&numberOfPunctChars);
featureSet.register(&ratioOfDigitsToChars);
featureSet.register(&hasUnbalancedParens);
// lockingTextWriter() just makes an output range from
// an output stream.
import std.stdio;
auto output = stdout.lockingTextWriter;
featureSet.apply(output, "hello world");
// As another example, you can use an Appender as well:
import std.array : Appender;
auto app = Appender!(char[])();
featureSet.apply(app, "goodbye moon");
writefln!"Appender's content:\n%s"(app.data);
}
Ali
