cs330_f2016:rackethof2
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cs330_f2016:rackethof2 [2016/09/12 20:47] morse |
cs330_f2016:rackethof2 [2021/06/30 23:42] (current) |
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| * ''default-parms'' - decorates a function to add default parameter values | * ''default-parms'' - decorates a function to add default parameter values | ||
| * ''type-parms'' - decorates a function to enforce parameter type checking | * ''type-parms'' - decorates a function to enforce parameter type checking | ||
| + | * ''new-sin2'' - a decorated version of your earlier ''new-sin'' that fills in default parameters and enforces correct types for all parameters | ||
| You will also chain these together to add both parameter type checking and default parameters to a function. | You will also chain these together to add both parameter type checking and default parameters to a function. | ||
| Line 43: | Line 44: | ||
| (define g (type-parms f (list number? string?)) | (define g (type-parms f (list number? string?)) | ||
| </code> | </code> | ||
| - | would result in a function ''g'' such that ''(g 0 "hello")'' behaves just like ''(f 0 "hello")'', but passing anything but a number for the first parameter or anything other than a string for the second parameter results in an error message. | + | would result in a function ''g'' such that ''(g 0 "hello")'' behaves just like ''(f 0 "hello")'', but passing anything but a number for the first parameter or anything other than a string for the second parameter results in an error message, by calling ``(error "ERROR MSG")``. |
| Hint: You may want to write a small helper function that takes a list of values and a list of type predicates, then makes sure each of the values satisfies the respective type predicate. This is straightforward to write recursively. Can you write it in shorter form by mapping a two-parameter function pairwise on the lists? | Hint: You may want to write a small helper function that takes a list of values and a list of type predicates, then makes sure each of the values satisfies the respective type predicate. This is straightforward to write recursively. Can you write it in shorter form by mapping a two-parameter function pairwise on the lists? | ||
| Line 55: | Line 56: | ||
| <code racket> | <code racket> | ||
| (define g (default-parms | (define g (default-parms | ||
| - | (type-parms f | + | (type-parms |
| - | (list number? string?)) | + | f |
| - | (list 0 ""))) | + | (list number? string?)) |
| + | (list 0 ""))) | ||
| </code> | </code> | ||
| would result in a function ''g'' that fills in any missing parameters with ''0'' and ''""'' respectively, and then verifies that the passed parameters are a number and a string. | would result in a function ''g'' that fills in any missing parameters with ''0'' and ''""'' respectively, and then verifies that the passed parameters are a number and a string. | ||
| Line 64: | Line 66: | ||
| * uses ''0'' and '''radians'' as defaults for the parameters, and | * uses ''0'' and '''radians'' as defaults for the parameters, and | ||
| * verifies that the first parameter is a number and that the second parameter is a symbol. | * verifies that the first parameter is a number and that the second parameter is a symbol. | ||
| + | This must be created using ''default-parms'' and ''type-parms'', not hand-coded. | ||
| ---- | ---- | ||
| Line 71: | Line 74: | ||
| You again **do not** need to bulletproof the code to enforce proper inputs. | You again **do not** need to bulletproof the code to enforce proper inputs. | ||
| Your code only needs to return correct values given correct inputs. | Your code only needs to return correct values given correct inputs. | ||
| + | |||
| + | Note: catching incorrectly typed inputs is part of the specified functionality for the ''type-parms'' decorator, so the functions generated by it should specifically detect and report that type of error. | ||
| ---- | ---- | ||
| - | |||
| ====Hints:==== | ====Hints:==== | ||
| - | For both of your decorators, they have the same basic form: | + | Remember from class that our decorators have the same basic form: |
| <code racket> | <code racket> | ||
| (define (<name of the decorator> f ...) | (define (<name of the decorator> f ...) | ||
| Line 83: | Line 87: | ||
| (apply f args))) | (apply f args))) | ||
| </code> | </code> | ||
| - | |||
cs330_f2016/rackethof2.1473713234.txt.gz · Last modified: 2021/06/30 23:40 (external edit)
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