Advanced Programming Guide

10 • Chapter 2: Procedures, Variables, and Extending Maple122107060112000000000The procedure f returns fractions rather than floating-point numbersso you must compose it with evalf; that is, use evalf(f()). Alternatively,you can perform this operation by using Maple’s composition operator,@.> (evalf @ f)();6.648630719The following uniform procedure uses evalf to evaluate the constantsin the range specification, r, to floating-point numbers, the map commandto multiply both endpoints of the range by 10^Digits, and round toround the results to integers.> uniform := proc( r::constant..constant )> local intrange, f;> intrange := map( x -> round(x*10^Digits), evalf(r) );> f := rand( intrange );> (evalf @ eval(f)) / 10^Digits;> end proc:You can now generate random floating-point numbers between 4and 7.> U := uniform(4..7):> seq( U(), i=1..20 );4.559076346, 4.939267370, 5.542851096, 4.260060897,4.976009937, 5.598293374, 4.547350944,5.647078832, 5.133877918, 5.249590037,4.120953928, 6.836344299, 5.374608653,4.586266491, 5.481365622, 5.384244382,5.190575456, 5.207535837, 5.553710879,4.163815544The uniform procedure has a serious flaw: uniform uses the currentvalue of Digits to construct intrange; thus, U depends on the value ofDigits when uniform creates it. On the other hand, the evalf commandwithin U uses the value of Digits that is current when you invoke U. Thesetwo values are not always identical.