Proof: Write Stmt Tab Unchanged Expr41

Let's prove the following theorem:

if the following are true:
  • the line at time 41 = 4
  • the tab at time 41 = 2
  • statement at line 4, tab 2 = self."last_name" = last_name
  • expression state at time 41 = "end_expr"

then the tab at time 42 = 2

Proof:

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Given
1 the line at time 41 = 4
2 the tab at time 41 = 2
3 statement at line 4, tab 2 = self."last_name" = last_name
4 expression state at time 41 = "end_expr"
Proof Table
# Claim Reason
1 the tab at time (41 + 1) = the tab at time 41 if the line at time 41 = 4 and the tab at time 41 = 2 and statement at line 4, tab 2 = self."last_name" = last_name and expression state at time 41 = "end_expr", then the tab at time (41 + 1) = the tab at time 41
2 the tab at time (41 + 1) = 2 if the tab at time (41 + 1) = the tab at time 41 and the tab at time 41 = 2, then the tab at time (41 + 1) = 2
3 41 + 1 = 42 41 + 1 = 42
4 the tab at time (41 + 1) = the tab at time 42 if 41 + 1 = 42, then the tab at time (41 + 1) = the tab at time 42
5 the tab at time 42 = 2 if the tab at time (41 + 1) = the tab at time 42 and the tab at time (41 + 1) = 2, then the tab at time 42 = 2

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