61 lines
2.5 KiB
Plaintext
61 lines
2.5 KiB
Plaintext
#!/usr/local/bin/spar
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pragma annotate( summary, "mapping" )
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@( description, "The task is to write a function/subroutine/... that takes" )
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@( description, "two ranges and a real number, and returns the mapping of" )
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@( description, "the real number from the first to the second range. Use" )
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@( description, "this function to map values from the range [0, 10] to the" )
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@( description, "range [-1, 0]." )
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@( see_also, "http://rosettacode.org/wiki/Map_range" )
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@( author, "Ken O. Burtch" );
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pragma license( unrestricted );
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pragma restriction( no_external_commands );
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procedure mapping is
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type first_range is new float;
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type second_range is new float;
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-- Spar doesn't implement ranges so we'll use constants
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first_range_first : constant first_range := 0.0;
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first_range_last : constant first_range := 10.0;
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second_range_first : constant second_range := -1.0;
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second_range_last : constant second_range := 0.0;
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function translate (first_range_value : first_range) return second_range is
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b1 : constant float := float( second_range_first );
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b2 : constant float := float( second_range_last );
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a1 : constant float := float( first_range_first );
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a2 : constant float := float( first_range_last );
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result : float;
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begin
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result := b1 + (float (first_range_value) - a1) * (b2 - b1) / (a2 - a1);
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return second_range(result);
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end translate;
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function translate_back (second_range_value : second_range) return first_range is
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b1 : constant float := float (first_range_first);
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b2 : constant float := float (first_range_last);
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a1 : constant float := float (second_range_first);
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a2 : constant float := float (second_range_last);
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result : float;
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begin
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result := b1 + (float (second_range_value) - a1) * (b2 - b1) / (a2 - a1);
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return first_range (result);
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end translate_back;
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test_value : first_range := first_range_first;
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translated_value : second_range;
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translated_back_value : first_range;
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begin
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loop
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translated_value := translate( test_value );
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translated_back_value := translate_back( translated_value );
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? strings.image(test_value) & " maps to: "
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& strings.image (translated_value);
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? strings.image(translated_value) & " maps back to: "
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& strings.image (translated_back_value);
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exit when test_value = first_range_last;
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test_value := @ + 1.0;
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end loop;
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end mapping;
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