A procedure gives a process a name.
Build a useful operation from smaller ones and watch names become parameters when the procedure is applied.
How does a procedure definition turn an expression into a reusable method?
- Read a procedure definition as parameters plus a body
- Follow one compound procedure application
- Distinguish a name from the value bound to it
square names a one-parameter procedure. sum-of-squares then combines two applications of square. The definition records a method. Nothing in its body runs until the procedure is applied.
On application, each parameter is bound to an argument value in a new environment. The body is evaluated with those bindings, producing 25 for inputs 3 and 4.
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- Value
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The first program returns 25 and produces no output.
Find the two square applications. They use different x bindings even though both calls evaluate the same procedure body.
Change the program and compare the result.
Define sum-of-cubes using a cube procedure, then evaluate it for 2 and 3.
Show hint
Keep the combining procedure independent from the details of cubing one value.