1 let (++) f g x = f (g x);;
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3 let rec fold_nat f x n = if n = 0 then x else f (fold_nat f x (n-1)) n ;;
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5 let print_hline = Console.print_hline;;
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18 let delta = L(A(V 0, V 0));;
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21 let rec aux l1 l2 t1 t2 = match t1, t2 with
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22 | L t1, L t2 -> aux l1 l2 t1 t2
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23 | L t1, t2 -> aux l1 (l2+1) t1 t2
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24 | t1, L t2 -> aux (l1+1) l2 t1 t2
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25 | V a, V b -> a + l1 = b + l2
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26 | A(t1,t2), A(u1,u2) -> aux l1 l2 t1 u1 && aux l1 l2 t2 u2
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29 let eta_eq = eta_eq' 0 0;;
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31 (* is arg1 eta-subterm of arg2 ? *)
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33 let rec aux lev t = eta_eq' lev 0 u t || match t with
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34 | L t -> aux (lev+1) t
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35 | A(t1, t2) -> aux lev t1 || aux lev t2
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40 (* does NOT lift the argument *)
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41 let mk_lams = fold_nat (fun x _ -> L x) ;;
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44 let string_of_bvar =
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45 let bound_vars = ["x"; "y"; "z"; "w"; "q"] in
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46 let bvarsno = List.length bound_vars in
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47 fun nn -> if nn < bvarsno then List.nth bound_vars nn else "x" ^ (string_of_int (nn - bvarsno + 1)) in
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48 let rec string_of_term_w_pars level = function
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49 | V v -> if v >= level then "`" ^ string_of_int (v-level) else
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50 string_of_bvar (level - v-1)
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53 | L _ as t -> "(" ^ string_of_term_no_pars level t ^ ")"
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55 and string_of_term_no_pars_app level = function
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56 | A(t1,t2) -> string_of_term_no_pars_app level t1 ^ " " ^ string_of_term_w_pars level t2
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57 | _ as t -> string_of_term_w_pars level t
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58 and string_of_term_no_pars level = function
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59 | L t -> "λ" ^ string_of_bvar level ^ ". " ^ string_of_term_no_pars (level+1) t
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60 | _ as t -> string_of_term_no_pars_app level t
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61 in string_of_term_no_pars 0
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69 ; sigma : (var * t) list (* substitutions *)
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70 ; stepped : var list
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71 ; phase : [`One | `Two] (* :'( *)
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74 let string_of_problem p =
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76 "[stepped] " ^ String.concat " " (List.map string_of_int p.stepped);
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77 "[DV] " ^ string_of_t p.div;
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78 "[CV] " ^ string_of_t p.conv;
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80 String.concat "\n" lines
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83 exception Done of (var * t) list (* substitution *);;
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84 exception Fail of int * string;;
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86 let problem_fail p reason =
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87 print_endline "!!!!!!!!!!!!!!! FAIL !!!!!!!!!!!!!!!";
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88 print_endline (string_of_problem p);
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89 raise (Fail (-1, reason))
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92 let freshvar ({freshno} as p) =
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93 {p with freshno=freshno+1}, freshno+1
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98 | A(t,_) -> is_inert t
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104 let rec get_inert = function
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106 | A(t, _) -> let hd,args = get_inert t in hd,args+1
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107 | _ -> assert false
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110 (* precomputes the number of leading lambdas in a term,
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111 after replacing _v_ w/ a term starting with n lambdas *)
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112 let rec no_leading_lambdas v n = function
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113 | L t -> 1 + no_leading_lambdas (v+1) n t
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114 | A _ as t -> let v', m = get_inert t in if v = v' then max 0 (n - m) else 0
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115 | V v' -> if v = v' then n else 0
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119 let rec subst level delift sub =
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121 | V v -> if v = level + fst sub then lift level (snd sub) else V (if delift && v > level then v-1 else v)
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122 | L t -> let t = subst (level + 1) delift sub t in if t = B then B else L t
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124 let t1 = subst level delift sub t1 in
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125 let t2 = subst level delift sub t2 in
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128 and mk_app t1 t2 = if t2 = B || (t1 = delta && t2 = delta) then B
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131 | L t1 -> subst 0 true (0, t2) t1
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136 | V m -> V (if m >= lev then m + n else m)
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137 | L t -> L (aux (lev+1) t)
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138 | A (t1, t2) -> A (aux lev t1, aux lev t2)
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142 let subst = subst 0 false;;
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144 let subst_in_problem ((v, t) as sub) p =
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145 print_endline ("-- SUBST " ^ string_of_t (V v) ^ " |-> " ^ string_of_t t);
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147 div=subst sub p.div;
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148 conv=subst sub p.conv;
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149 stepped=v::p.stepped;
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150 sigma=sub::p.sigma}
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153 let get_subterm_with_head_and_args hd_var n_args =
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154 let rec aux lev = function
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155 | C | V _ | B -> None
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156 | L t -> aux (lev+1) t
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158 let hd_var', n_args' = get_inert t1 in
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159 if hd_var' = hd_var + lev && n_args <= 1 + n_args'
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160 (* the `+1` above is because of t2 *)
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161 then Some (lift ~-lev t)
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162 else match aux lev t2 with
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163 | None -> aux lev t1
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164 | Some _ as res -> res
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168 let rec purify = function
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169 | L t -> Pure.L (purify t)
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170 | A (t1,t2) -> Pure.A (purify t1, purify t2)
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172 | C -> Pure.V (min_int/2)
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176 let check p sigma =
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177 print_endline "Checking...";
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178 let div = purify p.div in
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179 let conv = purify p.conv in
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180 let sigma = List.map (fun (v,t) -> v, purify t) sigma in
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181 let freshno = List.fold_right (max ++ fst) sigma 0 in
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182 let env = Pure.env_of_sigma freshno sigma in
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183 assert (Pure.diverged (Pure.mwhd (env,div,[])));
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184 print_endline " D diverged.";
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185 assert (not (Pure.diverged (Pure.mwhd (env,conv,[]))));
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186 print_endline " C converged.";
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191 print_endline (string_of_problem p); (* non cancellare *)
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192 if p.conv = B then problem_fail p "p.conv diverged";
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193 if p.div = B then raise (Done p.sigma);
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194 if p.phase = `Two && p.div = delta then raise (Done p.sigma);
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195 if not (is_inert p.div) then problem_fail p "p.div converged";
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199 (* drops the arguments of t after the n-th *)
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200 (* FIXME! E' usato in modo improprio contando sul fatto
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201 errato che ritorna un inerte lungo esattamente n *)
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202 let inert_cut_at n t =
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207 let k', t' = aux t1 in
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208 if k' = n then n, t'
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210 | _ -> assert false
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214 (* return the index of the first argument with a difference
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215 (the first argument is 0)
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216 precondition: p.div and t have n+1 arguments
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218 let find_eta_difference p t argsno =
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219 let t = inert_cut_at argsno t in
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220 let rec aux t u k = match t, u with
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221 | V _, V _ -> problem_fail p "no eta difference found (div subterm of conv?)"
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222 | A(t1,t2), A(u1,u2) ->
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223 if not (eta_eq t2 u2) then (k-1)
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224 else aux t1 u1 (k-1)
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225 | _, _ -> assert false
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226 in aux p.div t argsno
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229 let compute_max_lambdas_at hd_var j =
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230 let rec aux hd = function
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232 (if get_inert t1 = (hd, j)
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233 then max ( (*FIXME*)
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234 if is_inert t2 && let hd', j' = get_inert t2 in hd' = hd
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235 then let hd', j' = get_inert t2 in j - j'
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236 else no_leading_lambdas hd_var j t2)
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237 else id) (max (aux hd t1) (aux hd t2))
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238 | L t -> aux (hd+1) t
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240 | _ -> assert false
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244 let print_cmd s1 s2 = print_endline (">> " ^ s1 ^ " " ^ s2);;
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246 (* eat the arguments of the divergent and explode.
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247 It does NOT perform any check, may fail if done unsafely *)
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249 print_cmd "EAT" "";
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250 let var, k = get_inert p.div in
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252 | C | L _ | B | A _ -> assert false
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254 let phase = p.phase in
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259 (compute_max_lambdas_at var (k-1) p.div)
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260 (compute_max_lambdas_at var (k-1) p.conv) in
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261 (* apply fresh vars *)
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262 let p, t = fold_nat (fun (p, t) _ ->
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263 let p, v = freshvar p in
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266 let p = {p with phase=`Two} in
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267 let t = A(t, delta) in
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268 let t = fold_nat (fun t m -> A(t, V (k-m))) t (k-1) in
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269 let subst = var, mk_lams t k in
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270 let p = subst_in_problem subst p in
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271 let _, args = get_inert p.div in
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272 {p with div = inert_cut_at (args-k) p.div}
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274 let subst = var, mk_lams delta k in
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275 subst_in_problem subst p in
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279 (* step on the head of div, on the k-th argument, with n fresh vars *)
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281 let var, _ = get_inert p.div in
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282 print_cmd "STEP" ("on " ^ string_of_t (V var) ^ " (of:" ^ string_of_int n ^ ")");
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283 let p, t = (* apply fresh vars *)
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284 fold_nat (fun (p, t) _ ->
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285 let p, v = freshvar p in
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286 p, A(t, V (v + k + 1))
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288 let t = (* apply unused bound variables V_{k-1}..V_1 *)
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289 fold_nat (fun t m -> A(t, V (k-m+1))) t k in
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290 let t = mk_lams t (k+1) in (* make leading lambdas *)
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291 let subst = var, t in
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292 let p = subst_in_problem subst p in
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297 let hd_var, n_args = get_inert p.div in
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298 match get_subterm_with_head_and_args hd_var n_args p.conv with
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301 let phase = p.phase in
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304 then problem_fail p "Auto.2 did not complete the problem"
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306 with Done sigma -> sigma)
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308 let j = find_eta_difference p t n_args in
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310 (compute_max_lambdas_at hd_var j p.div)
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311 (compute_max_lambdas_at hd_var j p.conv) in
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312 let p = step j k p in
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316 let problem_of (label, div, convs, ps, var_names) =
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318 let rec aux lev = function
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319 | `Lam(_, t) -> L (aux (lev+1) t)
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320 | `I (v, args) -> Listx.fold_left (fun x y -> mk_app x (aux lev y)) (aux lev (`Var v)) args
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321 | `Var(v,_) -> if v >= lev && List.nth var_names (v-lev) = "C" then C else V v
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322 | `N _ | `Match _ -> assert false in
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323 assert (List.length ps = 0);
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324 let convs = List.rev convs in
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325 let conv = List.fold_left (fun x y -> mk_app x (aux 0 (y :> Num.nf))) (V (List.length var_names)) convs in
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326 let var_names = "@" :: var_names in
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327 let div = match div with
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328 | Some div -> aux 0 (div :> Num.nf)
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329 | None -> assert false in
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330 let varno = List.length var_names in
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331 let p = {orig_freshno=varno; freshno=1+varno; div; conv; sigma=[]; stepped=[]; phase=`One} in
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332 (* initial sanity check *)
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337 if eta_subterm p.div p.conv
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338 then print_endline "!!! div is subterm of conv. Problem was not run !!!"
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339 else check p (auto p)
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342 Problems.main (solve ++ problem_of);
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344 (* Example usage of interactive: *)
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346 (* let interactive div conv cmds =
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347 let p = problem_of div conv in
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349 let p = List.fold_left (|>) p cmds in
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351 let nth spl n = int_of_string (List.nth spl n) in
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353 let s = read_line () in
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354 let spl = Str.split (Str.regexp " +") s in
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355 s, let uno = List.hd spl in
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356 try if uno = "eat" then eat
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357 else if uno = "step" then step (nth spl 1) (nth spl 2)
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358 else failwith "Wrong input."
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359 with Failure s -> print_endline s; (fun x -> x) in
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360 let str, cmd = read_cmd () in
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361 let cmds = (" " ^ str ^ ";")::cmds in
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363 let p = cmd p in f p cmds
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365 | Done _ -> print_endline "Done! Commands history: "; List.iter print_endline (List.rev cmds)
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367 ) with Done _ -> ()
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370 (* interactive "x y"
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371 "@ (x x) (y x) (y z)" [step 0 1; step 0 2; eat]
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