A normal map function is defined for a specific array element type. To use a map function for arbitary types it must be defined with a template. A template can define the map function for a given array element type. For this purpose 'GENERIC_MAP_FUNCTION' uses the type parameter 'elementType':

const proc: GENERIC_MAP_FUNCTION (in type: elementType) is func
  local
    var type: arrayType is void;
  begin
    arrayType := array elementType;

    const func arrayType: doMap (in arrayType: anArray,
        inout elementType: aVariable, ref func elementType: anExpression) is func

      result
        var arrayType: mappedArray is 0 times elementType.value;
      begin
        for aVariable range anArray do
          mappedArray &:= anExpression;
        end for;
      end func;

  end func;

The body of 'GENERIC_MAP_FUNCTION' contains a definition of 'doMap'. Seed7 templates must be instanciated explizit. E.g.:

GENERIC_MAP_FUNCTION(float);
GENERIC_MAP_FUNCTION(string);
GENERIC_MAP_FUNCTION(time);

Assume that 'word' is a string variable. Now

doMap([]("apple", "pear", "apricot", "melon"), word, word & "s")

will return

[]("apples", "pears", "apricots", "melons")

Other possible calls of 'doMap' are:

doMap([] (1.2, 2.3, 3.4), x, x + 1.0)
doMap(thing, word,  "a " & word)
doMap(birthdays, z, z + 1 . YEARS)