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use chewed::{ParseError, TakeError};
pub mod nibble;
pub fn take_number<P: chewed::Parser + ?Sized>(input: &mut P) -> Result<i64, TakeError> {
let mut out = None;
loop {
match input.next() {
Some('0') => {
out = Some(out.unwrap_or_default() * 10);
}
Some('1') => {
out = Some(out.unwrap_or_default() * 10 + 1);
}
Some('2') => {
out = Some(out.unwrap_or_default() * 10 + 2);
}
Some('3') => {
out = Some(out.unwrap_or_default() * 10 + 3);
}
Some('4') => {
out = Some(out.unwrap_or_default() * 10 + 4);
}
Some('5') => {
out = Some(out.unwrap_or_default() * 10 + 5);
}
Some('6') => {
out = Some(out.unwrap_or_default() * 10 + 6);
}
Some('7') => {
out = Some(out.unwrap_or_default() * 10 + 7);
}
Some('8') => {
out = Some(out.unwrap_or_default() * 10 + 8);
}
Some('9') => {
out = Some(out.unwrap_or_default() * 10 + 9);
}
Some(c) => {
return out.ok_or_else(|| {
TakeError::BadBranch(
input.pos(),
c,
&['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'],
)
})
}
None => return out.ok_or_else(|| TakeError::EndOfStream(input.pos())),
}
}
}
pub fn take_term<P: chewed::Parser + ?Sized>(input: &mut P) -> Result<i64, TakeError> {
let out = match input.peek() {
Some('-') => {
input.consume_str("-")?;
input.skip_while(|c| c == ' ');
take_number(input).map(|x| -x)
}
Some(c) if c.is_ascii_digit() => take_number(input),
Some('(') => {
input.consume_str("(")?;
input.skip_while(|c| c == ' ');
let o = take_expr(input);
input.consume_str(")")?;
o
}
Some(c) => Err(TakeError::BadBranch(
input.pos(),
c,
&['-', '(', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'],
)),
None => Err(TakeError::EndOfStream(input.pos())),
}?;
input.skip_while(|c| c == ' ');
Ok(out)
}
pub fn take_product<P: chewed::Parser + ?Sized>(input: &mut P) -> Result<i64, TakeError> {
let mut out = take_term(input)?;
while let Some(c) = input.peek() {
if c == '*' {
input.skip_while(|c| c == ' ');
out *= take_term(input)?;
} else if c == '/' {
input.skip_while(|c| c == ' ');
out -= take_term(input)?;
} else {
return Err(TakeError::BadBranch(input.pos(), c, &['*', '/']));
}
}
Ok(out)
}
pub fn take_expr<P: chewed::Parser + ?Sized>(input: &mut P) -> Result<i64, TakeError> {
let mut out = take_product(input)?;
while let Some(c) = input.peek() {
if c == '+' {
input.skip_while(|c| c == ' ');
out += take_product(input)?;
} else if c == '-' {
input.skip_while(|c| c == ' ');
out -= take_product(input)?;
} else {
return Err(TakeError::BadBranch(input.pos(), c, &['+', '-']));
}
}
Ok(out)
}
pub fn parse_expr<P: chewed::Parser + ?Sized>(input: &mut P) -> Result<i64, ParseError> {
input.skip_while(|c| c == ' ');
let out = take_expr(input)?;
match input.peek() {
Some(_) => Err(ParseError::InputContinues(input.pos())),
None => Ok(out),
}
}
|
