filled scan sets initial value

changelog.md

@@ -10,6 +10,9 @@ This version is not yet released. If you are reading this on the website, then t
   - This new behavior is more useful
 - **Breaking Change**: [`un °`](https://uiua.org/docs/un) [`json`](https://uiua.org/docs/json) no longer attempts to form multidimensional arrays
   - This makes deserializing JSON more consistent
+- **Breaking Change**: [`fill ⬚`](https://uiua.org/docs/fill)ed [`scan \\`](https://uiua.org/docs/scan) now sets the initial value as well as filling row shapes
+  - This behavior is hard to get otherwise
+  - Fixes to existing code should be simple
 - Stabilize [`sort ⍆`](https://uiua.org/docs/sort)
   - Sorting is a very common operation, and it's useful to have such simple access to it
 - Stabilize [`last ⊣`](https://uiua.org/docs/last)

site/src/primitive.rs

@@ -186,7 +186,7 @@ fn all_fills() -> impl IntoView {
             { fill_row(Reshape, "Fills excess elements", "⬚0↯ 2_4 [1 2 3]") }
             { fill_row(Rotate, "Fills instead of wrapping", "⬚0↻ 2 [1 2 3 4 5]") }
             { fill_row(Reduce, "Sets initial value", "⬚10/+ [1 2 3]") }
-            { fill_row(Scan, "Fills row shapes", "⬚10\\⊂ [1 2 3]") }
+            { fill_row(Scan, "Sets initial value and fills row shapes", "⬚10\\⊂ [1 2 3]") }
             { fill_row(Rows, "Fills row shapes", "⬚0≡⇡ [4 7 3]") }
             { fill_row(Each, "Fills row shapes", "⬚0∵⇡ [3_2 2_4]") }
             { fill_row(Partition, "Fills row shapes", "⬚@ ⊜∘ ≠@ . \"Hey there\"") }

src/algorithm/reduce.rs

@@ -663,6 +663,9 @@ pub fn scan(ops: Ops, env: &mut Uiua) -> UiuaResult {
     if xs.rank() == 0 && f.sig.args <= 2 {
         return Err(env.error(format!("Cannot {} rank 0 array", Primitive::Scan.format())));
     }
+    if env.value_fill().is_some() {
+        return generic_scan(f, xs, env);
+    }
     match (f.node.as_flipped_primitive(), xs) {
         (Some((prim, flipped)), Value::Num(nums)) => {
             let arr = match prim {
@@ -771,12 +774,19 @@ fn generic_scan(f: SigNode, xs: Value, env: &mut Uiua) -> UiuaResult {
         ))),
         2 => {
             if xs.row_count() == 0 {
-                env.push(xs.first_dim_zero());
+                env.push(
+                    env.value_fill()
+                        .cloned()
+                        .unwrap_or_else(|| (xs.first_dim_zero())),
+                );
                 return Ok(());
             }
             let row_count = xs.row_count();
             let mut rows = xs.into_rows();
-            let mut acc = rows.next().unwrap();
+            let mut acc = env
+                .value_fill()
+                .cloned()
+                .unwrap_or_else(|| rows.next().unwrap());
             let mut scanned = Vec::with_capacity(row_count);
             scanned.push(acc.clone());
             env.without_fill(|env| -> UiuaResult {

src/primitive/defs.rs

@@ -1852,6 +1852,13 @@ primitive!(
     /// ex: ⊕□\+=@    . "Everyday man's on the block"
     ///   : ⊕□\+↻¯1=@ . "Everyday man's on the block"
     ///
+    /// [fill] both sets the initial value and fills mismatched shapes if necessary.
+    /// ex:    \+ [1 2 3 4 5]
+    ///   : ⬚@a\+ [1 2 3 4 5]
+    /// ex: +1⇡5
+    ///   : ⬚0\⊂ .
+    ///   : ↘1_1 .
+    ///
     /// If the function takes more than 2 arguments, additional arguments above the array on the stack will be passed to the function on every iteration.
     /// ex: \(+×) 10 [1 2 3 4]
     /// ex: ⬚@ \(⊂⊂) @, "abcd"

tests/loops.ua

@@ -130,7 +130,7 @@ A ← ↯2_3_4⇡24
 
 # Scan
 ⍤⤙≍ [1 3 6 10] \+[1 2 3 4]
-⍤⤙≍ [1_0_0 1_2_0 1_2_3] ⬚0\⊂ [1 2 3]
+⍤⤙≍ [0_0_0_0 0_1_0_0 0_1_2_0 0_1_2_3] ⬚0\⊂ [1 2 3]
 ⍤⤙≍ [1 2 3 4 5] °\+[1 3 6 10 15]
 ⍤⤙≍ [1_2_3 4_5_6 7_8_9] °\+[1_2_3 5_7_9 12_15_18]
 ⍤⤙≍ ⊃(⊂⊢:≡/=◫2.|°\=) [1 0 1 1 0]

todo.md

@@ -3,7 +3,6 @@
 ## 0.14
 The next version of Uiua
 
-- Code macro auto-repr
 - Stabilize `backward`, `case`
 - Optimize `group`/`partition` reduction replacement
 - Compile-time code string evaluation