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+---
+epic: 5
+story: 5.3
+title: "Previous Line Reference"
+status: draft
+---
+
+## Epic 5 — Variables, Line References & Aggregators
+**Goal:** Transform the notepad into a lightweight computational document.
+
+### Story 5.3: Previous Line Reference
+
+As a **CalcPad user**,
+I want to use `prev` or `ans` to reference the result of the immediately preceding line,
+So that I can chain calculations naturally without tracking line numbers or variable names.
+
+**Acceptance Criteria:**
+
+**Given** line 1 evaluates to `50`
+**When** the user writes `prev * 2` on line 2
+**Then** the result on line 2 is `100`
+
+**Given** line 1 evaluates to `50`
+**When** the user writes `ans + 10` on line 2
+**Then** the result on line 2 is `60`
+
+**Given** `prev` is used on line 1 (the very first line)
+**When** the engine evaluates the sheet
+**Then** the engine reports an error such as "no previous line" (there is no preceding result)
+
+**Given** line 3 is a comment or blank line, and line 4 uses `prev`
+**When** the engine evaluates the sheet
+**Then** `prev` resolves to the most recent line above that produced a numeric result (e.g., line 2)
+
+**Given** line 2 uses `prev` referencing line 1, and the user inserts a new line between them
+**When** the engine re-evaluates
+**Then** `prev` on the original line now references the newly inserted line (it always means "the line directly above")
+
+**Given** line 1 evaluates to `$50` (with currency)
+**When** line 2 uses `prev + $25`
+**Then** the result is `$75` with the currency context preserved