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A set of class notes from the spring 2002 cs 403 course. The notes cover topics such as subprograms, parameter matching, default parameters, and overloading. The two major types of subprograms: procedures and functions, and the design issues related to them, including parameter matching, parameter passing methods, and semantics. The notes also cover the concept of default parameters and their implications for parameter matching.
Typology: Study notes
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th
rd
Two major types:– Procedures: No return values– Functions: Have return values– Observation: No procedures in C – everything is a function
-^
Design issues:– Already addressed issues related to local variable
allocation, scope, etc.
Giving a parameter a default value:– int foo(int x = 0);– foo() means that x is initialized to 0.– Parameters are resolved positionally in this case.
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What about:– int foo(int x, int y = 0, char c = ‘ ‘);– foo(1,2,’c’); foo(1,2); foo(1) all ok.– foo(1,’c’) is a problem.
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What about the following:– int foo(int x, int y = 0, char c)– This won’t compile – makes no sense if resolved positionally
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L to R matching means that there must be 3 parameters regardless tomatch with the right one in this case
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Keyword parameters would be better in the context of defaultparameters (but not available in C++)
value
reflected in the caller
reflected in the caller
Copy:– Can be expensive for large structures (e.g., arrays)– Best fit with IN semantics
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Reference:– Cheap in most cases– Best fit with IN OUT semantics
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What if you want IN semantics but without theexpense?– Implement compiler checking scheme to prevent changes
to parameters
Copy vs. Reference Gives Different Results on IN OUTParameters int x;void foo(IN-OUT int y){
x++;y++; } void main(void){
x = 10;foo(x);cout << x << endl; } •^
If IN-OUT implemented by copy, then output is 11.
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If IN-OUT implemented by reference, then output is 12.
their parameters
other parameters
Reusing the same function name for multiplefunctions
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Functions must have different signatures (i.e.,parameter lists)
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Example:– foo(int a, int b, int c)– foo(float x, float y)
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Functions disambiguated based on parameter lists
