125 lines
3.3 KiB
Common Lisp
Executable File
125 lines
3.3 KiB
Common Lisp
Executable File
#!/usr/bin/env -S conlang -r false
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//! A simple five-function pn calculator
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enum Expr {
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Atom(f64),
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Op(char, [Expr]),
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}
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/// executes an expression
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fn execute(expr: Expr) -> f64 {
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match expr {
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Expr::Atom(value) => value,
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Expr::Op('*', [lhs, rhs]) => execute(lhs) * execute(rhs),
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Expr::Op('/', [lhs, rhs]) => execute(lhs) / execute(rhs),
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Expr::Op('%', [lhs, rhs]) => execute(lhs) % execute(rhs),
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Expr::Op('+', [lhs, rhs]) => execute(lhs) + execute(rhs),
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Expr::Op('-', [lhs, rhs]) => execute(lhs) - execute(rhs),
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Expr::Op('>', [lhs, rhs]) => (execute(lhs) as u64 >> execute(rhs) as u64) as f64,
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Expr::Op('<', [lhs, rhs]) => (execute(lhs) as u64 << execute(rhs) as u64) as f64,
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Expr::Op('-', [lhs]) => - execute(lhs),
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other => {
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panic("Unknown operation: " + fmt(other))
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}
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}
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}
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/// Pretty-prints an expression
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fn fmt_expr(expr: Expr) -> str {
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match expr {
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Expr::Atom(value) => fmt(value),
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Expr::Op(operator, [lhs, rhs]) => fmt('(', fmt_expr(lhs), ' ', operator, ' ', fmt_expr(rhs), ')'),
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Expr::Op(operator, [rhs]) => fmt(operator, fmt_expr(rhs)),
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_ => println("Unexpected expr: ", expr),
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}
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}
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fn print_expr(expr: Expr) {
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println(fmt_expr(expr))
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}
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/// Parses expressions
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fn parse(line: [char], power: i32) -> (Expr, [char]) {
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fn map((expr, line): (Expr, [char]), f: fn(Expr) -> Expr) -> (Expr, [char]) {
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(f(expr), line)
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}
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line = space(line);
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let (lhs, line) = match line {
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['0'..='9', ..] => number(line),
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['(', ..rest] => match parse(rest, Power::None) {
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(expr, [')', ..rest]) => (expr, rest),
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(expr, rest) => panic(fmt("Expected ')', got ", expr, ", ", rest)),
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},
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[op, ..rest] => parse(rest, pre_bp(op)).map(|lhs| Expr::Op(op, [lhs])),
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_ => panic("Unexpected end of input"),
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};
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while let [op, ..rest] = space(line) {
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let (before, after) = inf_bp(op);
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if before < power {
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break;
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};
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(lhs, line) = parse(rest, after).map(|rhs| Expr::Op(op, [lhs, rhs]));
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};
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(lhs, line)
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}
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fn number(line: [char]) -> (Expr, [char]) {
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let value = 0.0;
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while (let [first, ..rest] = line) && (let '0'..='9' = first) {
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(value, line) = (value * 10.0 + (first as f64 - '0' as f64), rest)
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} else (Expr::Atom(value), line)
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}
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fn space(line: [char]) -> [char] {
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match line {
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[' ', ..rest] => space(rest),
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['\n', ..rest] => space(rest),
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line => line
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}
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}
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enum Power {
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None,
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Shift,
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Factor,
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Term,
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Exponent,
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Unary,
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}
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fn inf_bp(op: char) -> (i32, i32) {
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(|x| (2 * x, 2 * x + 1))(
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match op {
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'*' => Power::Term,
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'/' => Power::Term,
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'%' => Power::Term,
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'+' => Power::Factor,
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'-' => Power::Factor,
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'>' => Power::Shift,
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'<' => Power::Shift,
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_ => Power::None,
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})
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}
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fn pre_bp(op: char) -> i32 {
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(|x| 2 * x + 1)(
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match op {
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'-' => Power::Unary,
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_ => panic("Unknown unary operator: " + op),
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})
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}
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fn main() {
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loop {
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let line = get_line("calc >");
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let (expr, rest) = line.chars().parse(0);
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println(fmt_expr(expr), " -> ", execute(expr));
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}
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}
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