--- pl:prolog:pllib:evaluator [2019/06/27 15:50]
+++ pl:prolog:pllib:evaluator [2019/06/27 15:50] (aktualna)
@@ Linia 1: / Linia 1: @@
+====== Evaluator ======
+{{tag>math arithmetic}}
+===== Description =====
+Evaluator which traverses the structure of the evaluated term, where variables are represented by Prolog atoms like a, b or c, so they do not correspond to Prolog variables.
+**Source**:  Guide to Prolog Programming (on-line tutorial)
+===== Download =====
+Program source code: {{evaluator.pl}}
+===== Listing =====
+<code prolog>
+eval(A+B,CV):-eval(A,AV),eval(B,BV),CV is AV+BV.
+eval(A-B,CV):-eval(A,AV),eval(B,BV),CV is AV-BV.
+eval(A*B,CV):-eval(A,AV),eval(B,BV),CV is AV*BV.
+eval(Num,Num):-number(Num).
+eval_v(A+B,CV,Vars):-eval_v(A,AV,Vars),eval_v(B,BV,Vars),CV is AV+BV.
+eval_v(A-B,CV,Vars):-eval_v(A,AV,Vars),eval_v(B,BV,Vars),CV is AV-BV.
+eval_v(A*B,CV,Vars):-eval_v(A,AV,Vars),eval_v(B,BV,Vars),CV is AV*BV.
+eval_v(Num,Num,Vars):-number(Num).
+eval_v(Var,Value,Vars):-atom(Var),member(Var/Value,Vars).
+% Try ?-eval_v(2*a+b,Val,[a/1,b/5]) to test the above program.</code>
+===== Comments =====

pl/prolog/pllib/evaluator.txt · ostatnio zmienione: 2019/06/27 15:50 (edycja zewnętrzna)

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