Time for an 2014 update…

Task/Parsing-Shunting-yard-algorithm/Haskell/parsing-shunting-yard-algorithm-1.hs

@@ -9,7 +9,8 @@ prec "-" = 2
 leftAssoc "^" = False
 leftAssoc _ = True
 
-isOp t = t `elem` (map (:[]) "-+/*^")
+isOp (t:[]) = t `elem` "-+/*^"
+isOp _      = False
 
 simSYA xs = final ++ [lastStep]
   where final = scanl f ([],[],"") xs

Task/Parsing-Shunting-yard-algorithm/Liberty-BASIC/parsing-shunting-yard-algorithm.liberty

@@ -0,0 +1,115 @@
+global stack$,queue$
+stack$=""
+queue$=""
+
+in$ = "3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3"
+print "Input:"
+print in$
+
+token$ = "#"
+print "No", "token", "stack", "queue"
+
+while 1
+    i=i+1
+    token$ = word$(in$, i)
+    if token$ = "" then i=i-1: exit while
+    print i, token$, reverse$(stack$), queue$
+
+    select case
+    case token$ = "("
+        call stack.push token$
+
+    case token$ = ")"
+        while stack.peek$() <> "("
+            'if stack is empty
+            if stack$="" then print "Error: no matching '(' for token ";i: end
+            call queue.push stack.pop$()
+        wend
+        discard$=stack.pop$()   'discard "("
+
+    case isOperator(token$)
+        op1$=token$
+        while(isOperator(stack.peek$()))
+            op2$=stack.peek$()
+            select case
+            case op2$<>"^" and precedence(op1$) = precedence(op2$)
+                '"^" is the only right-associative operator
+                call queue.push stack.pop$()
+            case precedence(op1$) < precedence(op2$)
+                call queue.push stack.pop$()
+            case else
+                exit while
+            end select
+        wend
+        call stack.push op1$
+
+    case else   'number
+        'actually, wrong operator could end up here, like say %
+        'If the token is a number, then add it to the output queue.
+        call queue.push token$
+    end select
+
+wend
+
+while stack$<>""
+    if stack.peek$() = "(" then print "no matching ')'": end
+    call queue.push stack.pop$()
+wend
+
+print "Output:"
+while queue$<>""
+    print queue.pop$();" ";
+wend
+print
+
+end
+
+'------------------------------------------
+function isOperator(op$)
+    isOperator = instr("+-*/^", op$)<>0 AND len(op$)=1
+end function
+
+function precedence(op$)
+    if isOperator(op$) then
+        precedence = 1 _
+            + (instr("+-*/^", op$)<>0) _
+            + (instr("*/^", op$)<>0) _
+            + (instr("^", op$)<>0)
+    end if
+end function
+
+'------------------------------------------
+sub stack.push s$
+    stack$=s$+"|"+stack$
+end sub
+
+sub queue.push s$
+    queue$=queue$+s$+"|"
+end sub
+
+function queue.pop$()
+    'it does return empty on empty stack or queue
+    queue.pop$=word$(queue$,1,"|")
+    queue$=mid$(queue$,instr(queue$,"|")+1)
+end function
+
+function stack.pop$()
+    'it does return empty on empty stack or queue
+    stack.pop$=word$(stack$,1,"|")
+    stack$=mid$(stack$,instr(stack$,"|")+1)
+end function
+
+function stack.peek$()
+    'it does return empty on empty stack or queue
+    stack.peek$=word$(stack$,1,"|")
+end function
+
+function reverse$(s$)
+    reverse$ = ""
+    token$="#"
+    while token$<>""
+        i=i+1
+        token$=word$(s$,i,"|")
+        reverse$ = token$;" ";reverse$
+    wend
+end function