Update HOME_EXAM.md

HOME_EXAM.md

@@ -232,12 +232,21 @@ illegal stuff;
 - c, command
 - v, variable
 - e, expression
+- t, type
 
 ##### Expression can be either a
 - b, boolean 
 - i, integer 
 - f, function 
 
+##### Types are
+- i32, integer
+- bool, boolean
+- (), Unit
+- &t, reference to type
+- &mut t, mutable reference to type
+- *t, dereference to type
+
 ### Function sequence
 ```math
 <f, σ>⇓σ'
@@ -245,12 +254,12 @@ illegal stuff;
 
 ### Command sequence
 ```math
-\frac{<c1,σ> ⇓ σ' <c2,σ'> ⇓ σ''}{<c1;c2,σ> ⇓ σ''}
+\frac{<c_1,σ> ⇓ σ' <c_2,σ'> ⇓ σ''}{<c_1;c_2,σ> ⇓ σ''}
 ```
 
 ### Operands for integer expressions
 ```math
-\frac{<e1,σ> ⇓ n1 <e2, σ> ⇓ n2}{<e1 + e2, σ> ⇓ n1 \text{ plus } n2}
+\frac{<e_1,σ> ⇓ i_1 <e_2, σ> ⇓ i_2}{<e_1 + e2, σ> ⇓ i_1 \text{ plus } i_2}
 ```
 The other integer expressions are
 - -, minus
@@ -265,7 +274,7 @@ The other integer expressions are
 
 ### Operands for boolean expressions
 ```math
-\frac{<e1,σ> ⇓ b1 <e2, σ> ⇓ b2}{<e1 == e2, σ> ⇓ b1 \text{ equal } b2}
+\frac{<e_1,σ> ⇓ b_1 <e_2, σ> ⇓ b_2}{<e_1 == e_2, σ> ⇓ b_1 \text{ equal } b_2}
 ```
 Other boolean expressions are
 - "==", equal
@@ -294,12 +303,15 @@ Other boolean expressions are
 ```
 
 ### Let expression
-
 ```math
 \frac{<v, σ>⇓<\text{let } v:=e, σ>⇓σ'}{<\text{let } v := e, σ> ⇓ σ[v := e]}
 ```
 
-### If expression
+### Assign expression
+```math
+{<v := e, σ> ⇓ σ[v := e]}
+```
+
 
 
 - Explain (in text) what an interpretation of your example should produce, do that by dry running your given example step by step. Relate back to the SOS rules. You may skip repetitions to avoid cluttering.