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Parsing/RPN calculator algorithm: Difference between revisions
add Rust solution
(add Rust solution) |
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Line 4,422:
Push Opr / to stack: 3 1.22070312e-4
Push Opr + to stack: 3.00012207</pre>
=={{header|Rust}}==
<lang rust>fn rpn(text: &str) -> f64 {
let tokens = text.split_whitespace();
let mut stack: Vec<f64> = vec![];
println!("input operation stack");
for token in tokens {
print!("{:^5} ", token);
match token.parse() {
Ok(num) => {
stack.push(num);
println!("push {:?}", stack);
}
Err(_) => {
match token {
"+" => {
let b = stack.pop().expect("missing first operand");
let a = stack.pop().expect("missing second operand");
stack.push(a + b);
}
"-" => {
let b = stack.pop().expect("missing first operand");
let a = stack.pop().expect("missing second operand");
stack.push(a - b);
}
"*" => {
let b = stack.pop().expect("missing first operand");
let a = stack.pop().expect("missing second operand");
stack.push(a * b);
}
"/" => {
let b = stack.pop().expect("missing first operand");
let a = stack.pop().expect("missing second operand");
stack.push(a / b);
}
"^" => {
let b = stack.pop().expect("missing first operand");
let a = stack.pop().expect("missing second operand");
stack.push(a.powf(b));
}
_ => panic!("unknown operator {}", token),
}
println!("calculate {:?}", stack);
}
}
}
stack.pop().unwrap_or(0.0)
}
fn main() {
let text = "3 4 2 * 1 5 - 2 3 ^ ^ / +";
println!("\nresult: {}", rpn(text));
}</lang>
{{out}}
<pre>input operation stack
3 push [3.0]
4 push [3.0, 4.0]
2 push [3.0, 4.0, 2.0]
* calculate [3.0, 8.0]
1 push [3.0, 8.0, 1.0]
5 push [3.0, 8.0, 1.0, 5.0]
- calculate [3.0, 8.0, -4.0]
2 push [3.0, 8.0, -4.0, 2.0]
3 push [3.0, 8.0, -4.0, 2.0, 3.0]
^ calculate [3.0, 8.0, -4.0, 8.0]
^ calculate [3.0, 8.0, 65536.0]
/ calculate [3.0, 0.0001220703125]
+ calculate [3.0001220703125]
result: 3.0001220703125
</pre>
=={{header|Scala}}==
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