How to use the bs-platform/lib/js/string.js.sub function in bs-platform

}
    } else if (pattern$1 === "") {
      return /* [] */0;
    } else {
      var match = $$String.contains_from(path$1, 1, /* "/" */47);
      var match$1;
      if (match !== 0) {
        var nextUrlSlash = $$String.index_from(path$1, 1, /* "/" */47);
        var urlItem = $$String.sub(path$1, 1, nextUrlSlash - 1 | 0);
        match$1 = /* tuple */[
          urlItem,
          $$String.sub(path$1, nextUrlSlash, path$1.length - nextUrlSlash | 0)
        ];
      } else {
        match$1 = /* tuple */[
          $$String.sub(path$1, 1, path$1.length - 1 | 0),
          ""
        ];
      }
      var match$2 = $$String.contains_from(pattern$1, 1, /* "/" */47);
      var match$3;
      if (match$2 !== 0) {
        var nextPatternSlash = $$String.index_from(pattern$1, 1, /* "/" */47);
        var patternItem = $$String.sub(pattern$1, 1, nextPatternSlash - 1 | 0);
        match$3 = /* tuple */[
          patternItem,
          $$String.sub(pattern$1, nextPatternSlash, pattern$1.length - nextPatternSlash | 0)
        ];
      } else {
        match$3 = /* tuple */[
          $$String.sub(pattern$1, 1, pattern$1.length - 1 | 0),
          ""

var urlItem = $$String.sub(path$1, 1, nextUrlSlash - 1 | 0);
        match$1 = /* tuple */[
          urlItem,
          $$String.sub(path$1, nextUrlSlash, path$1.length - nextUrlSlash | 0)
        ];
      } else {
        match$1 = /* tuple */[
          $$String.sub(path$1, 1, path$1.length - 1 | 0),
          ""
        ];
      }
      var match$2 = $$String.contains_from(pattern$1, 1, /* "/" */47);
      var match$3;
      if (match$2 !== 0) {
        var nextPatternSlash = $$String.index_from(pattern$1, 1, /* "/" */47);
        var patternItem = $$String.sub(pattern$1, 1, nextPatternSlash - 1 | 0);
        match$3 = /* tuple */[
          patternItem,
          $$String.sub(pattern$1, nextPatternSlash, pattern$1.length - nextPatternSlash | 0)
        ];
      } else {
        match$3 = /* tuple */[
          $$String.sub(pattern$1, 1, pattern$1.length - 1 | 0),
          ""
        ];
      }
      _pathsAndPatterns = /* :: */[
        /* tuple */[
          match$1[0],
          match$3[0]
        ],
        pathsAndPatterns

$$String.sub(path$1, 1, path$1.length - 1 | 0),
          ""
        ];
      }
      var match$2 = $$String.contains_from(pattern$1, 1, /* "/" */47);
      var match$3;
      if (match$2 !== 0) {
        var nextPatternSlash = $$String.index_from(pattern$1, 1, /* "/" */47);
        var patternItem = $$String.sub(pattern$1, 1, nextPatternSlash - 1 | 0);
        match$3 = /* tuple */[
          patternItem,
          $$String.sub(pattern$1, nextPatternSlash, pattern$1.length - nextPatternSlash | 0)
        ];
      } else {
        match$3 = /* tuple */[
          $$String.sub(pattern$1, 1, pattern$1.length - 1 | 0),
          ""
        ];
      }
      _pathsAndPatterns = /* :: */[
        /* tuple */[
          match$1[0],
          match$3[0]
        ],
        pathsAndPatterns
      ];
      _pattern = match$3[1];
      _path = match$1[1];
      continue ;
      
    }
  };

if (match$1) {
            var s = $$String.sub(patternHead, 1, patternHead.length - 1 | 0);
            params[s] = pathHead;
            _pathsAndPatterns = rest;
            _search = s + ("=" + (pathHead + ("&" + search)));
            continue ;
            
          } else {
            _pathsAndPatterns = rest;
            continue ;
            
          }
        } else {
          var match$2 = hasSearch(patternHead);
          if (match$2) {
            var s$1 = $$String.sub(patternHead, 1, patternHead.length - 1 | 0);
            params[s$1] = pathHead;
            var search$1 = "?" + (s$1 + ("=" + (pathHead + ("&" + search))));
            return /* record */[
                    /* search */search$1,
                    /* hash */hash,
                    /* params */params
                  ];
          } else {
            var search$2 = "?" + search;
            return /* record */[
                    /* search */search$2,
                    /* hash */hash,
                    /* params */params
                  ];
          }
        }

var pattern$1 = _pattern;
    var path$1 = _path;
    if (path$1 === "") {
      if (pattern$1 === "") {
        return pathsAndPatterns;
      } else {
        return /* [] */0;
      }
    } else if (pattern$1 === "") {
      return /* [] */0;
    } else {
      var match = $$String.contains_from(path$1, 1, /* "/" */47);
      var match$1;
      if (match !== 0) {
        var nextUrlSlash = $$String.index_from(path$1, 1, /* "/" */47);
        var urlItem = $$String.sub(path$1, 1, nextUrlSlash - 1 | 0);
        match$1 = /* tuple */[
          urlItem,
          $$String.sub(path$1, nextUrlSlash, path$1.length - nextUrlSlash | 0)
        ];
      } else {
        match$1 = /* tuple */[
          $$String.sub(path$1, 1, path$1.length - 1 | 0),
          ""
        ];
      }
      var match$2 = $$String.contains_from(pattern$1, 1, /* "/" */47);
      var match$3;
      if (match$2 !== 0) {
        var nextPatternSlash = $$String.index_from(pattern$1, 1, /* "/" */47);
        var patternItem = $$String.sub(pattern$1, 1, nextPatternSlash - 1 | 0);
        match$3 = /* tuple */[

function isPathCompliant(pathsAndPatterns) {
  var normalizedPathsAndPatterns;
  if (pathsAndPatterns) {
    var match = pathsAndPatterns[0];
    var path = match[0];
    var match$1 = hasHash(path);
    normalizedPathsAndPatterns = match$1 ? /* :: */[
        /* tuple */[
          $$String.sub(path, 0, match$1[0]),
          match[1]
        ],
        pathsAndPatterns[1]
      ] : pathsAndPatterns;
  } else {
    normalizedPathsAndPatterns = pathsAndPatterns;
  }
  return List.for_all((function (param) {
                var pattern = param[1];
                var match = hasSearch(pattern);
                if (match) {
                  return /* true */1;
                } else {
                  return +(param[0] === pattern);
                }
              }), normalizedPathsAndPatterns);

function of_substring$1(s, pos, len) {
  return Caml_format.caml_int32_of_string($$String.sub(s, pos, len));
}

function of_substring$3(s, pos, len) {
  return Caml_format.caml_nativeint_of_string($$String.sub(s, pos, len));
}

function of_substring(s, pos, len) {
  return Caml_format.caml_int_of_string($$String.sub(s, pos, len));
}