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Prototype tokenizer+parser for update function expressions.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,4 +1,4 @@ | ||
| pub mod bma_fn_tree; | ||
| mod enums; | ||
| mod parser; | ||
| mod tokenizer; | ||
| pub mod enums; | ||
| pub mod parser; | ||
| pub mod tokenizer; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1 +1,268 @@ | ||
| // todo | ||
| use crate::update_fn::bma_fn_tree::*; | ||
| use crate::update_fn::enums::*; | ||
| use crate::update_fn::tokenizer::{try_tokenize_bma_formula, BmaFnToken}; | ||
|
|
||
| /// Parse an BMA update function formula string representation into an actual expression tree. | ||
| /// Basically a wrapper for tokenize+parse (used often for testing/debug purposes). | ||
| /// | ||
| /// NEEDS to call [validate_props] to fully finish the preprocessing step. | ||
| pub fn parse_bma_formula(formula: &str) -> Result<BmaFnNode, String> { | ||
| let tokens = try_tokenize_bma_formula(formula.to_string())?; | ||
| let tree = parse_bma_fn_tokens(&tokens)?; | ||
| Ok(tree) | ||
| } | ||
|
|
||
| /// Utility method to find the first occurrence of a specific token in the token tree. | ||
| fn index_of_first(tokens: &[BmaFnToken], token: BmaFnToken) -> Option<usize> { | ||
| return tokens.iter().position(|t| *t == token); | ||
| } | ||
|
|
||
| /// Parse `tokens` of BMA update fn formula into an abstract syntax tree using recursive steps. | ||
| pub fn parse_bma_fn_tokens(tokens: &[BmaFnToken]) -> Result<BmaFnNode, String> { | ||
| parse_1_div(tokens) | ||
| } | ||
|
|
||
| /// Recursive parsing step 1: extract `/` operators. | ||
| fn parse_1_div(tokens: &[BmaFnToken]) -> Result<BmaFnNode, String> { | ||
| let div_token = index_of_first(tokens, BmaFnToken::Binary(ArithOp::Div)); | ||
| Ok(if let Some(i) = div_token { | ||
| BmaFnNode::mk_arithmetic( | ||
| parse_2_mul(&tokens[..i])?, | ||
| parse_1_div(&tokens[(i + 1)..])?, | ||
| ArithOp::Div, | ||
| ) | ||
| } else { | ||
| parse_2_mul(tokens)? | ||
| }) | ||
| } | ||
|
|
||
| /// Recursive parsing step 2: extract `*` operators. | ||
| fn parse_2_mul(tokens: &[BmaFnToken]) -> Result<BmaFnNode, String> { | ||
| let mul_token = index_of_first(tokens, BmaFnToken::Binary(ArithOp::Times)); | ||
| Ok(if let Some(i) = mul_token { | ||
| BmaFnNode::mk_arithmetic( | ||
| parse_3_minus(&tokens[..i])?, | ||
| parse_2_mul(&tokens[(i + 1)..])?, | ||
| ArithOp::Times, | ||
| ) | ||
| } else { | ||
| parse_3_minus(tokens)? | ||
| }) | ||
| } | ||
|
|
||
| /// Recursive parsing step 3: extract `-` operators. | ||
| fn parse_3_minus(tokens: &[BmaFnToken]) -> Result<BmaFnNode, String> { | ||
| let minus_token = index_of_first(tokens, BmaFnToken::Binary(ArithOp::Minus)); | ||
| Ok(if let Some(i) = minus_token { | ||
| BmaFnNode::mk_arithmetic( | ||
| parse_4_plus(&tokens[..i])?, | ||
| parse_3_minus(&tokens[(i + 1)..])?, | ||
| ArithOp::Minus, | ||
| ) | ||
| } else { | ||
| parse_4_plus(tokens)? | ||
| }) | ||
| } | ||
|
|
||
| /// Recursive parsing step 4: extract `+` operators. | ||
| fn parse_4_plus(tokens: &[BmaFnToken]) -> Result<BmaFnNode, String> { | ||
| let minus_token = index_of_first(tokens, BmaFnToken::Binary(ArithOp::Add)); | ||
| Ok(if let Some(i) = minus_token { | ||
| BmaFnNode::mk_arithmetic( | ||
| parse_5_others(&tokens[..i])?, | ||
| parse_4_plus(&tokens[(i + 1)..])?, | ||
| ArithOp::Add, | ||
| ) | ||
| } else { | ||
| parse_5_others(tokens)? | ||
| }) | ||
| } | ||
|
|
||
| /// Recursive parsing step 5: extract literals and recursively solve sub-formulae in parentheses | ||
| /// and in functions. | ||
| fn parse_5_others(tokens: &[BmaFnToken]) -> Result<BmaFnNode, String> { | ||
| if tokens.is_empty() { | ||
| Err("Expected formula, found nothing.".to_string()) | ||
| } else { | ||
| if tokens.len() == 1 { | ||
| // This should be name (var/function) or a parenthesis group, anything | ||
| // else does not make sense. | ||
| match &tokens[0] { | ||
| BmaFnToken::Atomic(Literal::Str(name)) => { | ||
| return Ok(BmaFnNode::mk_variable(name.as_str())); | ||
| } | ||
| BmaFnToken::Atomic(Literal::Int(num)) => { | ||
| return Ok(BmaFnNode::mk_constant(*num)); | ||
| } | ||
| BmaFnToken::Aggregate(operator, arguments) => { | ||
| let mut arg_expression_nodes = Vec::new(); | ||
| for inner in arguments { | ||
| // it must be a token list | ||
| if let BmaFnToken::TokenList(inner_token_list) = inner { | ||
| arg_expression_nodes.push(parse_bma_fn_tokens(inner_token_list)?); | ||
| } else { | ||
| return Err( | ||
| "Function must be applied on `BmaFnToken::TokenList` args." | ||
| .to_string(), | ||
| ); | ||
| } | ||
| } | ||
| return Ok(BmaFnNode::mk_aggregation( | ||
| operator.clone(), | ||
| arg_expression_nodes, | ||
| )); | ||
| } | ||
| BmaFnToken::Unary(operator, argument) => { | ||
| return if let BmaFnToken::TokenList(inner_token_list) = *argument.clone() { | ||
| Ok(BmaFnNode::mk_unary( | ||
| parse_bma_fn_tokens(&inner_token_list)?, | ||
| operator.clone(), | ||
| )) | ||
| } else { | ||
| return Err( | ||
| "Function must be applied on `BmaFnToken::TokenList` args.".to_string() | ||
| ); | ||
| } | ||
| } | ||
| // recursively solve sub-formulae in parentheses | ||
| BmaFnToken::TokenList(inner) => { | ||
| return parse_bma_fn_tokens(inner); | ||
| } | ||
| _ => {} // otherwise, fall through to the error at the end. | ||
| } | ||
| } | ||
| Err(format!("Unexpected: {tokens:?}. Expecting formula.")) | ||
| } | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
| use crate::update_fn::bma_fn_tree::BmaFnNode; | ||
| use crate::update_fn::enums::{AggregateOp, ArithOp, UnaryOp}; | ||
|
|
||
| #[test] | ||
| fn test_parse_simple_addition() { | ||
| let input = "3 + 5"; | ||
| let result = parse_bma_formula(input); | ||
| let expected = BmaFnNode::mk_arithmetic( | ||
| BmaFnNode::mk_constant(3), | ||
| BmaFnNode::mk_constant(5), | ||
| ArithOp::Add, | ||
| ); | ||
| assert_eq!(result, Ok(expected)); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_parse_simple_subtraction() { | ||
| let input = "10 - 7"; | ||
| let result = parse_bma_formula(input); | ||
| let expected = BmaFnNode::mk_arithmetic( | ||
| BmaFnNode::mk_constant(10), | ||
| BmaFnNode::mk_constant(7), | ||
| ArithOp::Minus, | ||
| ); | ||
| assert_eq!(result, Ok(expected)); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_parse_multiplication_and_division() { | ||
| let input = "8 * 4 / 2"; | ||
| let result = parse_bma_formula(input); | ||
| let expected = BmaFnNode::mk_arithmetic( | ||
| BmaFnNode::mk_arithmetic( | ||
| BmaFnNode::mk_constant(8), | ||
| BmaFnNode::mk_constant(4), | ||
| ArithOp::Times, | ||
| ), | ||
| BmaFnNode::mk_constant(2), | ||
| ArithOp::Div, | ||
| ); | ||
| assert_eq!(result, Ok(expected)); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_parse_nested_arithmetic() { | ||
| let input = "3 + (5 * 2)"; | ||
| let result = parse_bma_formula(input); | ||
| let expected = BmaFnNode::mk_arithmetic( | ||
| BmaFnNode::mk_constant(3), | ||
| BmaFnNode::mk_arithmetic( | ||
| BmaFnNode::mk_constant(5), | ||
| BmaFnNode::mk_constant(2), | ||
| ArithOp::Times, | ||
| ), | ||
| ArithOp::Add, | ||
| ); | ||
| assert_eq!(result, Ok(expected)); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_parse_abs_function() { | ||
| let input = "abs(5)"; | ||
| let result = parse_bma_formula(input); | ||
| let expected = BmaFnNode::mk_unary(BmaFnNode::mk_constant(5), UnaryOp::Abs); | ||
| assert_eq!(result, Ok(expected)); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_parse_aggregate_min() { | ||
| let input = "min(3, 5, 5 + variable)"; | ||
| let result = parse_bma_formula(input); | ||
| let expected = BmaFnNode::mk_aggregation( | ||
| AggregateOp::Min, | ||
| vec![ | ||
| BmaFnNode::mk_constant(3), | ||
| BmaFnNode::mk_constant(5), | ||
| BmaFnNode::mk_arithmetic( | ||
| BmaFnNode::mk_constant(5), | ||
| BmaFnNode::mk_variable("variable"), | ||
| ArithOp::Add, | ||
| ), | ||
| ], | ||
| ); | ||
| assert_eq!(result, Ok(expected)); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_parse_unmatched_parentheses() { | ||
| let input = "3 + (5 * 2"; | ||
| let result = parse_bma_formula(input); | ||
| assert!(result.is_err()); | ||
| assert_eq!( | ||
| result, | ||
| Err("Expected ')' to previously encountered opening counterpart.".to_string()) | ||
| ); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_parse_invalid_token() { | ||
| let input = "5 + @"; | ||
| let result = parse_bma_formula(input); | ||
| assert!(result.is_err()); | ||
| assert_eq!(result, Err("Unexpected character: '@'".to_string())); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_parse_function_with_multiple_arguments() { | ||
| let input = "max(3, 5, 10)"; | ||
| let result = parse_bma_formula(input); | ||
| let expected = BmaFnNode::mk_aggregation( | ||
| AggregateOp::Max, | ||
| vec![ | ||
| BmaFnNode::mk_constant(3), | ||
| BmaFnNode::mk_constant(5), | ||
| BmaFnNode::mk_constant(10), | ||
| ], | ||
| ); | ||
| assert_eq!(result, Ok(expected)); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_parse_empty_formula() { | ||
| let input = ""; | ||
| let result = parse_bma_formula(input); | ||
| assert!(result.is_err()); | ||
| assert_eq!(result, Err("Expected formula, found nothing.".to_string())); | ||
| } | ||
| } |
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