Data update

Task/Euler-method/DuckDB/euler-method.duckdb

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+# Declaration for the sake of euler_table()
+create or replace function cooling(x,y) as NULL;
+
+# Euler method assuming cooling/2 is available
+create or replace function euler_table(x_start, y_start, x2, h) as table (
+  with recursive cte as (
+    select x_start::DOUBLE as x, y_start::DOUBLE as y
+    union all
+    select x + h as x,
+           y + h*cooling(x, y)
+    from cte
+    where (x < x2 and x_start < x2) or
+          (x > x2 and x_start > x2)
+  )
+  from cte
+);
+
+create or replace function euler(x_start, y_start, x2, h) as (
+  select last(y order by x) from euler_method(x_start, y_start, x2, h)
+);
+
+## Example:
+create or replace function cooling(x,y) as
+  -0.07 * (y - 20);
+
+select h, euler(0,100, 100, h) from unnest([1,2,5,10,20]) _(h);