| 1 | module List = ListLabels |
| 2 | |
| 3 | module Spl : sig |
| 4 | type id = string |
| 5 | |
| 6 | type binop = |
| 7 | | Plus |
| 8 | | Minus |
| 9 | | Times |
| 10 | | Div |
| 11 | |
| 12 | type stm = |
| 13 | | CompoundStm of stm * stm |
| 14 | | AssignStm of id * exp |
| 15 | | PrintStm of exp list |
| 16 | and exp = |
| 17 | | IdExp of id |
| 18 | | NumExp of int |
| 19 | | OpExp of exp * binop * exp |
| 20 | | EseqExp of stm * exp |
| 21 | |
| 22 | val maxargs : stm -> int |
| 23 | end = struct |
| 24 | type id = string |
| 25 | |
| 26 | type binop = |
| 27 | | Plus |
| 28 | | Minus |
| 29 | | Times |
| 30 | | Div |
| 31 | |
| 32 | type stm = |
| 33 | | CompoundStm of stm * stm |
| 34 | | AssignStm of id * exp |
| 35 | | PrintStm of exp list |
| 36 | and exp = |
| 37 | | IdExp of id |
| 38 | | NumExp of int |
| 39 | | OpExp of exp * binop * exp |
| 40 | | EseqExp of stm * exp |
| 41 | |
| 42 | (* 01.p.1: Write ML function (maxargs : stm -> int) that tells the |
| 43 | * maximum number of arguments of any print statement within any |
| 44 | * subexpression of a given statement. For example, maxargs(prog) |
| 45 | * is 2. |
| 46 | *) |
| 47 | let maxargs stm = |
| 48 | let max = ref 0 in |
| 49 | let rec check_stm = function |
| 50 | | PrintStm exps -> |
| 51 | let exps_length = List.length exps in |
| 52 | if exps_length > !max then max := exps_length else (); |
| 53 | List.iter exps ~f:check_exp |
| 54 | | AssignStm (_, e) -> |
| 55 | check_exp e |
| 56 | | CompoundStm (s1, s2) -> |
| 57 | check_stm s1; |
| 58 | check_stm s2 |
| 59 | and check_exp = function |
| 60 | | IdExp _ | NumExp _ -> () |
| 61 | | OpExp (e1, _, e2) -> |
| 62 | check_exp e1; |
| 63 | check_exp e2 |
| 64 | | EseqExp (s, e) -> |
| 65 | check_stm s; |
| 66 | check_exp e |
| 67 | in |
| 68 | check_stm stm; |
| 69 | !max |
| 70 | end |
| 71 | |
| 72 | let spl_prog = |
| 73 | (* a := 5 + 3; |
| 74 | * b := (print(a, a - 1), 10 * a); |
| 75 | * print(b) |
| 76 | *) |
| 77 | Spl.CompoundStm |
| 78 | ( Spl.AssignStm ("a", Spl.OpExp (Spl.NumExp 5, Spl.Plus, Spl.NumExp 3)) |
| 79 | , Spl.CompoundStm |
| 80 | ( Spl.AssignStm |
| 81 | ( "b" |
| 82 | , Spl.EseqExp |
| 83 | ( Spl.PrintStm |
| 84 | [ Spl.IdExp "a" |
| 85 | ; Spl.OpExp (Spl.IdExp "a", Spl.Minus, Spl.NumExp 1) |
| 86 | ] |
| 87 | , Spl.OpExp (Spl.NumExp 10, Spl.Times, Spl.IdExp "a") |
| 88 | ) |
| 89 | ) |
| 90 | , Spl.PrintStm [Spl.IdExp "b"] |
| 91 | ) |
| 92 | ) |
| 93 | |
| 94 | let () = |
| 95 | Printf.printf "maxargs: %d\n" (Spl.maxargs spl_prog) |