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10. CVIČENIE Z PREDMETU ÚVOD DO DEKLARATÍVNEHO PROGRAMOVANIA http://ii.fmph.uniba.sk/cl/courses/udp/ex/ex10.cl |
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Dátum: streda 25. 4. 2006 Odporúčaná verzia CL: 5.81.16 WWW stránka predmetu: http://ii.fmph.uniba.sk/cl/courses/udp?lang=sk Kontakt na cvičiaceho: mailto:kluka@fmph.uniba.sk |
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Functionals are higher-order functions, i.e., functions whose arguments or results are functions. In some declarative programming languages (known as functional languages), functionals are the main tool of modularization. For example, one can define a functional for sorting lists where the first argument is a function used to compare the elements of the list . This kind of functionals can also be defined in some imperative languages, for example Pascal or C. In CL, we can only define first-order functions (all arguments are numbers). However, we can use the components theory and interpretation of a theory to achieve similar modularization as with functionals. Theories and interpretations resemble classes with virtual methods or interfaces from object-oriented programming. |
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Assignment 1. Define a mapping functional that applies any binary function on each element of the list . The argument is a parameter of the function . Formally, this is specified as or semiformally as To define the functional, insert below a new theory component and name it . Into the theory, insert a new binary function with an empty definition (such functions are called free ). Below insert a new binary function and define it to satisfy the above specification. |
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Remark. In CL, a string are lists of characters (see the definition of the formats and in the module ). Characters are enclosed in double quotes ( ), strings in single quotes ( ). You can use the formats to display a number as a character, and the format to display a list of numbers as a string, e.g.: 90 = c:Ch & 72,101,108,108,111,33,0 = y:Str In the exercises below we use the following convention for the names of variables:
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Assignment 2. Use the functional to define a function satisfying: semiformally To use the functional, insert below a new intepretation of the theory , uncheck the Local checkbox, and use _pair as the component identifier suffix. After clicking OK, CL inserts a copy of the theory with the function renamed to and the function renamed to . Your task is then to define the function in such a way that behaves as specified. |
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Remark. In combinatorial exercises (including exercise 2), we often define functions taking or yielding lists of lists ; It is therefore of advantage to display such objects by the format showing a result as a list of strings , since strings are lists of characters. |
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Try out the queries: (97,98,99,0),(100,101,0),0 = t:Ls and Map_pair("!",'abcde','123','?',0) = t:Ls
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Assignment 3. Define a function satisfying: Use the function from the preceding exercise. A possible test query is Interleave("$",'abcde') = t:Ls
which should produce . |
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Assignment 5. Define a function satisfying: Use the function from Assignment 1. Try out the format for the query Subseqlist('Jago') = t:Ls
which should yield a list containing in any order the strings ; , , , ; , , , , , ; , , , ; . |
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