Arithmetic evaluation: Difference between revisions

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 ? arithEvaluate("(1 + 2 / 2) * (5 + 5)")
 # value: 20.0</syntaxhighlight>
+=={{header|EasyLang}}==
+<syntaxhighlight lang="easylang">
+</syntaxhighlight>
+subr nch
+   if inp_ind > len inp$[]
+      ch$ = strchar 0
+   else
+      ch$ = inp$[inp_ind]
+      inp_ind += 1
+   .
+   ch = strcode ch$
+.
+#
+subr ntok
+   if ch = 0
+      tok$ = "eof"
+   else
+      while ch$ = " "
+         nch
+      .
+      if ch >= 48 and ch <= 58
+         tok$ = "n"
+         s$ = ""
+         while ch >= 48 and ch <= 58 or ch$ = "."
+            s$ &= ch$
+            nch
+         .
+         tokv = number s$
+      else
+         tok$ = ch$
+         nch
+      .
+   .
+.
+subr init0
+   a$[] = [ ]
+   ale[] = [ ]
+   ari[] = [ ]
+   err = 0
+.
+proc init s$ . .
+   inp$[] = strchars s$
+   inp_ind = 1
+   nch
+   ntok
+   init0
+.
+proc ast_print nd . .
+   write "AST: " & nd
+   for i to len a$[]
+      write " ( "
+      write a$[i] & " "
+      write ale[i] & " "
+      write ari[i]
+      write " )"
+   .
+   print ""
+.
+func node .
+   a$[] &= ""
+   ale[] &= 0
+   ari[] &= 0
+   return len a$[]
+.
+#
+funcdecl parse_expr .
+#
+func parse_factor .
+   if tok$ = "n"
+      nd = node
+      a$[nd] = "n"
+      ale[nd] = tokv
+      ntok
+   elif tok$ = "("
+      ntok
+      nd = parse_expr
+      if tok$ <> ")"
+         err = 1
+         print "error: ) expected, got " & tok$
+      .
+      ntok
+   .
+   return nd
+.
+func parse_term .
+   ndx = parse_factor
+   while tok$ = "*" or tok$ = "/"
+      nd = node
+      ale[nd] = ndx
+      a$[nd] = tok$
+      ntok
+      ari[nd] = parse_factor
+      ndx = nd
+   .
+   return ndx
+.
+func parse_expr .
+   ndx = parse_term
+   while tok$ = "+" or tok$ = "-"
+      nd = node
+      ale[nd] = ndx
+      a$[nd] = tok$
+      ntok
+      ari[nd] = parse_term
+      ndx = nd
+   .
+   return ndx
+.
+func parse s$ .
+   init s$
+   return parse_expr
+.
+func eval nd .
+   if a$[nd] = "n"
+      return ale[nd]
+   .
+   le = eval ale[nd]
+   ri = eval ari[nd]
+   a$ = a$[nd]
+   if a$ = "+"
+      return le + ri
+   elif a$ = "-"
+      return le - ri
+   elif a$ = "*"
+      return le * ri
+   elif a$ = "/"
+      return le / ri
+   .
+.
+repeat
+   inp$ = input
+   until inp$ = ""
+   print "Inp: " & inp$
+   nd = parse inp$
+   ast_print nd
+   if err = 0
+      print "Eval: " & eval nd
+   .
+   print ""
+.
+input_data
+* 6
+.2 * ((5.3+8)*3 + 4)
+.5 * 2 + 2 * 3.14
+{{out}}
+<pre>
+Inp: 4 * 6
+AST: 2 ( n 4 0 ) ( * 1 3 ) ( n 6 0 )
+Eval: 24
+Inp: 4.2 * ((5.3+8)*3 + 4)
+AST: 2 ( n 4.20 0 ) ( * 1 8 ) ( n 5.30 0 ) ( + 3 5 ) ( n 8 0 ) ( * 4 7 ) ( n 3 0 ) ( + 6 9 ) ( n 4 0 )
+Eval: 184.38
+Inp: 2.5 * 2 + 2 * 3.14
+AST: 4 ( n 2.50 0 ) ( * 1 3 ) ( n 2 0 ) ( + 2 6 ) ( n 2 0 ) ( * 5 7 ) ( n 3.14 0 )
+Eval: 11.28
+</pre>
 =={{header|Elena}}==