The measure as defined in the Porter algorithm.

measure.cc

/**
 * Computes the measure of an English word as defined for the Porter algorithm.
 * The definition of the measure can be found here:
 *    http://snowball.tartarus.org/algorithms/porter/stemmer.html
 *
 * ...but it's overtly complicated. Here's my definition:
 *
 * The *measure* of a word is the number of vowels followed by a consonant.
 *
 * Examples:
 *    Tree = 0     Orc = 1     Obama = 2     Treason = 2
 *    CCVV         VCC         VCVCV         CCVVCVC
 *
 * Usage
 * -----
 * Supply a single argument (an English word) to get its measure. Run with
 * no arguments for the tests.
 *
 * Compilation
 * -----------
 * clang++ -O3 -std=c++11 measure.cc -o measure
 */

#include <iostream>
#include <string>
#include <map>
#include <boost/algorithm/string.hpp>

using namespace std;

bool main_vowel(char c) {
    return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
}

bool vowel(const string &s, int idx) {
    return main_vowel(s[idx]) || (idx > 0 && s[idx] == 'y' && !vowel(s, idx-1));
}

bool consonant(const string &s, int idx) {
    return !vowel(s, idx);
}

unsigned int measure(string s) {
    boost::algorithm::to_lower(s);
    unsigned int m = 0;
    bool prev = vowel(s, 0);
    for (int i = 1; i < s.length(); ++i) {
        const bool curr = vowel(s, i);
        if (prev && !curr) {
            ++m;
        }
        prev = curr;
    }
    return m;
}

int main(int argc, char **argv) {
    if (argc == 1) {
        cout << "Running tests...\n";
        map<string, unsigned int> words
            {{"Tr", 0}, {"ee", 0}, {"TREE", 0}, {"y", 0}, {"BY", 0},
            {"trouble", 1}, {"oats", 1}, {"trees", 1}, {"ivy", 1},
            {"Troubles", 2}, {"private", 2}, {"OATEN", 2}, {"orrery", 2}};
        for (auto &x : words) {
            const unsigned int m = measure(x.first);
            cout << x.first << ": " << m;
            if (m != x.second) {
                cout << " -> WRONG!! Correct answer: " << x.second << endl;
                return 42;
            }
            cout << '\n';
        }
        cout << "All good!" << endl;
    } else {
        string word{argv[1]};
        cout << measure(word) << endl;
    }
    return 0;
}