Parsing/RPN to infix conversion: Difference between revisions
→{{header|Haskell}}
Line 1,729:
infix: ((1 + 2) ^ (3 + 4)) ^ (5 + 6)
</pre>
=={{header|Groovy}}==
{{trans|Java}}
<lang groovy>class PostfixToInfix {
static class Expression {
final static String ops = "-+/*^"
String op, ex
int precedence = 3
Expression(String e) {
ex = e
}
Expression(String e1, String e2, String o) {
ex = String.format "%s %s %s", e1, o, e2
op = o
precedence = (ops.indexOf(o) / 2) as int
}
@Override
String toString() {
return ex
}
}
static String postfixToInfix(final String postfix) {
Stack<Expression> expr = new Stack<>()
for (String token in postfix.split("\\s+")) {
char c = token.charAt(0)
int idx = Expression.ops.indexOf(c as int)
if (idx != -1 && token.length() == 1) {
Expression r = expr.pop()
Expression l = expr.pop()
int opPrecedence = (idx / 2) as int
if (l.precedence < opPrecedence || (l.precedence == opPrecedence && c == '^' as char))
l.ex = '(' + l.ex + ')'
if (r.precedence < opPrecedence || (r.precedence == opPrecedence && c != '^' as char))
r.ex = '(' + r.ex + ')'
expr << new Expression(l.ex, r.ex, token)
} else {
expr << new Expression(token)
}
printf "%s -> %s%n", token, expr
}
expr.peek().ex
}
static void main(String[] args) {
(["3 4 2 * 1 5 - 2 3 ^ ^ / +", "1 2 + 3 4 + ^ 5 6 + ^"]).each { String e ->
printf "Postfix : %s%n", e
printf "Infix : %s%n", postfixToInfix(e)
println()
}
}
}</lang>
{{out}}
<pre>Postfix : 3 4 2 * 1 5 - 2 3 ^ ^ / +
3 -> [3]
4 -> [3, 4]
2 -> [3, 4, 2]
* -> [3, 4 * 2]
1 -> [3, 4 * 2, 1]
5 -> [3, 4 * 2, 1, 5]
- -> [3, 4 * 2, 1 - 5]
2 -> [3, 4 * 2, 1 - 5, 2]
3 -> [3, 4 * 2, 1 - 5, 2, 3]
^ -> [3, 4 * 2, 1 - 5, 2 ^ 3]
^ -> [3, 4 * 2, (1 - 5) ^ 2 ^ 3]
/ -> [3, 4 * 2 / (1 - 5) ^ 2 ^ 3]
+ -> [3 + 4 * 2 / (1 - 5) ^ 2 ^ 3]
Infix : 3 + 4 * 2 / (1 - 5) ^ 2 ^ 3
Postfix : 1 2 + 3 4 + ^ 5 6 + ^
1 -> [1]
2 -> [1, 2]
+ -> [1 + 2]
3 -> [1 + 2, 3]
4 -> [1 + 2, 3, 4]
+ -> [1 + 2, 3 + 4]
^ -> [(1 + 2) ^ (3 + 4)]
5 -> [(1 + 2) ^ (3 + 4), 5]
6 -> [(1 + 2) ^ (3 + 4), 5, 6]
+ -> [(1 + 2) ^ (3 + 4), 5 + 6]
^ -> [((1 + 2) ^ (3 + 4)) ^ (5 + 6)]
Infix : ((1 + 2) ^ (3 + 4)) ^ (5 + 6)</pre>
=={{header|Haskell}}==
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