Seed7 Example: Generic map function

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Examples Generic map function

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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, in 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)

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