From 80ad3f392706c4f6bddd37d317b2519bd0d6f579 Mon Sep 17 00:00:00 2001
From: Ben Bridle <ben@derelict.engineering>
Date: Wed, 15 Oct 2025 14:12:37 +1300
Subject: Add find operator for expressions

The <fnd> operator returns the index of the first element in a list
with the given value.
---
 src/types/expression_stack.rs | 19 +++++++++++++++++++
 src/types/operator.rs         |  3 +++
 2 files changed, 22 insertions(+)

(limited to 'src')

diff --git a/src/types/expression_stack.rs b/src/types/expression_stack.rs
index f197ea7..e60dad7 100644
--- a/src/types/expression_stack.rs
+++ b/src/types/expression_stack.rs
@@ -69,6 +69,7 @@ impl ExpressionStack {
             Operator::BitNot           => {          pop!(a); push!(op_bit_not(a)) },
             Operator::Length           => {          pop!(a); push!(op_length(a)) },
             Operator::Index            => { pop!(b); pop!(a); push!(op_index(a, b)) },
+            Operator::Find             => { pop!(b); pop!(a); push!(op_find(a, b)) },
             Operator::Sum              => {          pop!(a); push!(op_sum(a)) },
             Operator::Absolute         => {          pop!(a); push!(op_absolute(a)) },
             Operator::Debug            => {          pop!(a); op_debug(&a, &source); push!(Ok(a)) },
@@ -192,6 +193,13 @@ fn op_index(l: IntermediateValue, r: IntermediateValue) -> Result<IntermediateVa
         false => Err(ExpressionError::IndexError(l.len(), r)),
     }
 }
+fn op_find(l: IntermediateValue, r: IntermediateValue) -> Result<IntermediateValue, ExpressionError> {
+    let l = to_list(l)?; let r = to_isize(r)?;
+    match l.iter().position(|e| *e == r) {
+        Some(i) => Ok(from_isize(i as isize)),
+        None => Err(ExpressionError::FindError(l.len(), r)),
+    }
+}
 fn op_sum(l: IntermediateValue) -> Result<IntermediateValue, ExpressionError> {
     let sum = match l {
         IntermediateValue::Integer(integer) => ones(*integer) as isize,
@@ -243,6 +251,8 @@ pub enum ExpressionError {
     InvalidArgumentType(&'static str, &'static str),
     // (length, index)
     IndexError(usize, isize),
+    // (length, value)
+    FindError(usize, isize),
 }
 
 
@@ -261,6 +271,15 @@ pub fn report_expression_error(error: &Tracked<ExpressionError>, source_code: &s
             &format!("Operator expected {expected} value, not {received} value"),
         ExpressionError::IndexError(length, index) =>
             &format!("Could not access element {index} from a list of length {length}"),
+        ExpressionError::FindError(length, value) => {
+            let mut character = String::new();
+            if let Ok(value) = u32::try_from(*value) {
+                if let Some(c) = char::from_u32(value) {
+                    character = format!(" (character '{c}')");
+                }
+            }
+            &format!("Could not find value {value}{character} in list of length {length}")
+        }
     };
 
     report_source_issue(LogLevel::Error, &context, message);
diff --git a/src/types/operator.rs b/src/types/operator.rs
index 5bf82b2..e94c67d 100644
--- a/src/types/operator.rs
+++ b/src/types/operator.rs
@@ -20,6 +20,7 @@ pub enum Operator {
     BitNot,
     Length,
     Index,
+    Find,
     Sum,
     Absolute,
     Debug,
@@ -62,6 +63,7 @@ impl Operator {
             "<not>" => Some(Operator::BitNot),
             "<len>" => Some(Operator::Length),
             "<nth>" => Some(Operator::Index),
+            "<fnd>" => Some(Operator::Find),
             "<sum>" => Some(Operator::Sum),
             "<abs>" => Some(Operator::Absolute),
             "<dbg>" => Some(Operator::Debug),
@@ -93,6 +95,7 @@ impl std::fmt::Display for Operator {
             Operator::BitNot           => "<not>",
             Operator::Length           => "<len>",
             Operator::Index            => "<nth>",
+            Operator::Find             => "<fnd>",
             Operator::Sum              => "<sum>",
             Operator::Absolute         => "<abs>",
             Operator::Debug            => "<dbg>",
-- 
cgit v1.2.3-70-g09d2