rpn(1): better error handling
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885f167afc
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83
src/rpn.rs
83
src/rpn.rs
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@ -45,7 +45,7 @@
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use std::{
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use std::{
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collections::VecDeque,
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collections::VecDeque,
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env::args,
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env::args,
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fmt,
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fmt::{ self, Display, Formatter },
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io::stdin,
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io::stdin,
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process::ExitCode,
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process::ExitCode,
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};
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};
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@ -70,19 +70,6 @@ enum CalcType {
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Empty,
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Empty,
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}
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}
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#[derive(Debug, Clone)]
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struct EvaluationError { pub message: String }
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impl fmt::Display for EvaluationError {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "{}", self.message)
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}
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}
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// I’m no math nerd but I want the highest possible approximation of 0.9
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// repeating and it seems this can give it to me
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const PRECISION_MOD: f64 = 0.9 + f64::EPSILON * 100.0;
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impl From<&str> for CalcType {
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impl From<&str> for CalcType {
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fn from(value: &str) -> Self {
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fn from(value: &str) -> Self {
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match value {
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match value {
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@ -103,15 +90,48 @@ impl From<&str> for CalcType {
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}
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}
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}
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}
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impl Display for CalcType {
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fn fmt(&self, f: &mut Formatter) -> fmt::Result {
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let y: String;
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write!(f, "{}", match self {
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Add => "addition",
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Subtract => "subtraction",
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Multiply => "multiplication",
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Divide => "division",
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Power => "exponentiation",
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Floor => "floor divion",
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Modulo => "modulus",
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Val(x) => {
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y = x.to_string(); &y
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},
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Empty => "",
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})
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}
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}
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#[derive(Debug, Clone)]
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struct EvaluationError { pub message: String }
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impl Display for EvaluationError {
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fn fmt(&self, f: &mut Formatter) -> fmt::Result {
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write!(f, "{}", self.message)
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}
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}
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// I’m no math nerd but I want the highest possible approximation of 0.9
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// repeating and it seems this can give it to me
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const PRECISION_MOD: f64 = 0.9 + f64::EPSILON * 100.0;
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fn eval(
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fn eval(
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input: &str,
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input: &str,
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initial_stack: VecDeque<f64>,
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initial_stack: VecDeque<f64>,
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) -> Result<VecDeque<f64>, EvaluationError> {
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) -> Result<(VecDeque<f64>, bool), EvaluationError> {
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let mut stack = initial_stack;
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let mut stack = initial_stack;
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let mut oper = false;
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if input.is_empty() {
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if input.is_empty() {
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stack.clear();
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stack.clear();
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return Ok(stack);
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return Ok((stack, oper));
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}
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}
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// Split the input into tokens.
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// Split the input into tokens.
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@ -122,7 +142,7 @@ fn eval(
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let x: CalcType = match CalcType::from(tok) {
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let x: CalcType = match CalcType::from(tok) {
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Empty => {
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Empty => {
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return Err(EvaluationError {
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return Err(EvaluationError {
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message: format!("Invalid token: {}", tok),
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message: format!("{}: Invalid token", tok),
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})
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})
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},
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},
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x => x,
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x => x,
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@ -136,13 +156,28 @@ fn eval(
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for op in &ops {
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for op in &ops {
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match op {
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match op {
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Val(v) => {
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Val(_) => {
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return Err(EvaluationError { message: format!(
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return Err(EvaluationError { message: format!(
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"{}: Unexpected value in the operator stack.",
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"{}: Unexpected value in the operator stack.",
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v
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op,
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)});
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)});
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},
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},
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_ => {
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_ => {
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if stack.len() < 2 {
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return Err(EvaluationError {
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message: format!("{}: Unexpected operation.", op)
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})
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}
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if stack.len() > ops.len() + 1 {
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return Err(
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EvaluationError { message: format!("Syntax error.")}
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);
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}
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oper = true;
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let (x, y) = (
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let (x, y) = (
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stack.pop_back().unwrap(),
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stack.pop_back().unwrap(),
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stack.pop_back().unwrap(),
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stack.pop_back().unwrap(),
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@ -162,7 +197,7 @@ fn eval(
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};
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};
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}
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}
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Ok(stack)
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Ok((stack, oper))
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}
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}
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// Round a float to the given precision level
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// Round a float to the given precision level
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@ -183,15 +218,17 @@ fn main() -> ExitCode {
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while let Ok(_) = stdin().read_line(&mut buf) {
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while let Ok(_) = stdin().read_line(&mut buf) {
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match eval(&buf.trim(), stack) {
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match eval(&buf.trim(), stack) {
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Ok(s) => {
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Ok(s) => {
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stack = s.clone();
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buf.clear();
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stack = s.0.clone();
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let val = match stack.iter().last() {
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let val = match stack.iter().last() {
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Some(v) => v,
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Some(v) => v,
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None => break,
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None => break,
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};
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};
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if s.1 == false { continue; }
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println!("{}", round_precise(val, precision).to_string());
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println!("{}", round_precise(val, precision).to_string());
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buf.clear();
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},
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},
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Err(err) => {
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Err(err) => {
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eprintln!("{}: {}", argv[0], err.message);
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eprintln!("{}: {}", argv[0], err.message);
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@ -209,7 +246,7 @@ fn main() -> ExitCode {
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match eval(&input, stack) {
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match eval(&input, stack) {
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Ok(s) => {
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Ok(s) => {
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stack = s.clone();
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stack = s.0.clone();
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let val = match stack.iter().last() {
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let val = match stack.iter().last() {
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Some(v) => v,
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Some(v) => v,
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