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core.ml
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core.ml
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open Format
open Syntax
open Support.Error
open Support.Pervasive
(* ------------------------ EVALUATION ------------------------ *)
exception NoRuleApplies
let rec ispos t = match t with
TmSucc(_,TmZero(_)) -> true
| TmSucc(_,t1) -> ispos t1
| _ -> false
let rec isneg t = match t with
TmPred(_,TmZero(_)) -> true
| TmPred(_,t1) -> isneg t1
| _ -> false
let rec isnumericval t = match t with
TmZero(_) -> true
| t when ispos t -> true
| t when isneg t -> true
| _ -> false
let rec isval t = match t with
TmTrue(_) -> true
| TmFalse(_) -> true
| t when isnumericval t -> true
| _ -> false
let rec eval1 t = match t with
TmIf(_,TmTrue(_),v2,v3) when (isval v2 && isval v3)->
v2
| TmIf(_,TmFalse(_),v2,v3) when (isval v2 && isval v3)->
v3
| TmIf(fi,t1,v2,v3) when (isval v2 && isval v3) ->
let t1' = eval1 t1 in
TmIf(fi, t1', v2, v3)
| TmIf(fi,t1,v2,t3) when (isval v2) ->
let t3' = eval1 t3 in
TmIf(fi, t1, v2, t3')
| TmIf(fi,t1,t2,t3) ->
let t2' = eval1 t2 in
TmIf(fi, t1, t2', t3)
| TmSucc(_,TmPred(_,nv1)) when (isnumericval nv1) ->
nv1
| TmPred(_,TmSucc(_,nv1)) when (isnumericval nv1) ->
nv1
| TmSucc(fi,t1) ->
let t1' = eval1 t1 in
TmSucc(fi, t1')
| TmPred(fi,t1) ->
let t1' = eval1 t1 in
TmPred(fi, t1')
| TmIsZero(_,TmZero(_)) ->
TmTrue(dummyinfo)
| TmIsZero(_,nv1) when (ispos nv1 || isneg nv1) ->
TmFalse(dummyinfo)
| TmIsZero(fi,t1) ->
let t1' = eval1 t1 in
TmIsZero(fi, t1')
| _ ->
raise NoRuleApplies
let rec eval t =
try let t' = eval1 t
in eval t'
with NoRuleApplies -> t