smltutorial

8/6/2019 smlTutorial

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8/6/2019 smlTutorial

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tutorial1.sml Page 2

(* applySomeFunc is implemented in the system called map *)(* Currying *)

(* add n to each element of the list *)

fun addN(n, y)= map (fn x=>x+n) y;addN(3, [1,2,3]);

(* add n to each element of the list, remove parenthesis *)fun incN n y = map (fn x=>x+n) y;incN 3[1,2,3];

(* define a convenient function name to increment 10 *)

fun add10 x = incN 10 x;add10 [1,2,3,4,5];

fun sumRealList(x:reallist):real=case x of

nil => 0.0 | y::ys => y + sumRealList(ys)

(* find the roots of ax^2 + bx + c = 0 *)

fun roots(a:real, b:real, c:real):real*real=

letval rt =Math.sqrt(b*b - 4.0*a*c)

in ((~b + rt) / (2.0* a), (~b - rt) / (2.0* a))end

fun month(n:int):string=case n of

1=> "January" |2=> "February" |3=> "March" |4=> "April" |5=> "May" |6=> "June"

|7=> "July" |8=> "August" |9=> "September" |10=> "October" |11=> "November" |12=> "December" |_=> "Bad month"

(* different style of coding a function *)

fun month1 1="January" | month1 2="February" | month1 3="March" | month1_="Bad month"

(* different style of coding a function *)

fun month2 x =if x =1then"January"

elseif x=2then"February" elseif x=3then"March" else"Bad month"