Parsing/Shunting-yard algorithm: Difference between revisions
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<pre>infix: 3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3
postfix: 3 4 2 * 1 5 - 2 3 ^ ^ / + </pre>
=={{header|Julia}}==
Translation from the Wikipedia reference article's pseudocode.
<lang julia>
function parseinfix2rpn(s)
outputq = []
opstack = []
infix = split(s)
for tok in infix
if all(isnumber, tok)
push!(outputq, tok)
elseif tok == "("
push!(opstack, tok)
elseif tok == ")"
while !isempty(opstack) && (op = pop!(opstack)) != "("
push!(outputq, op)
end
else # operator
while !isempty(opstack)
op = pop!(opstack)
if Base.operator_precedence(Symbol(op)) > Base.operator_precedence(Symbol(tok)) ||
(Base.operator_precedence(Symbol(op)) ==
Base.operator_precedence(Symbol(tok)) && op != "^")
push!(outputq, op)
else
push!(opstack, op) # undo peek
break
end
end
push!(opstack, tok)
end
println("The working output stack is $outputq")
end
while !isempty(opstack)
if (op = pop!(opstack)) == "("
throw("mismatched parentheses")
else
push!(outputq, op)
end
end
outputq
end
teststring = "3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3"
println("\nResult: $teststring becomes $(join(parseinfix2rpn(teststring), ' '))")
</lang>
{{output}}
<pre>
The working output stack is Any["3"]
The working output stack is Any["3"]
The working output stack is Any["3", "4"]
The working output stack is Any["3", "4"]
The working output stack is Any["3", "4", "2"]
The working output stack is Any["3", "4", "2", "*"]
The working output stack is Any["3", "4", "2", "*"]
The working output stack is Any["3", "4", "2", "*", "1"]
The working output stack is Any["3", "4", "2", "*", "1"]
The working output stack is Any["3", "4", "2", "*", "1", "5"]
The working output stack is Any["3", "4", "2", "*", "1", "5", "-"]
The working output stack is Any["3", "4", "2", "*", "1", "5", "-"]
The working output stack is Any["3", "4", "2", "*", "1", "5", "-", "2"]
The working output stack is Any["3", "4", "2", "*", "1", "5", "-", "2"]
The working output stack is Any["3", "4", "2", "*", "1", "5", "-", "2", "3"]
Result: 3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3 becomes 3 4 2 * 1 5 - 2 3 ^ ^ / +
</pre>
=={{header|Kotlin}}==
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