Documentation pop

nand2tetris/projects/7/VMTranslator/docs/popPointer.md

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+`push pointer i`
+----
+
+For `pointer` we get the _address_ pointed to by THIS/THAT.
+
+We translate 
+* `pointer 0` to `THIS` and
+* `pointer 1` to `THAT`. 
+
+Store it in `segmentPointer`. 
+
+Output
+----
+
+```
+addr <- segmentPointer      # D_eq_RAM_i.asm
+D <- RAM[addr]              # ^--
+RAM[SP] <- D                # RAM_SP_eq_D.asm
+SP++                        # SPpp.asm
+```

nand2tetris/projects/7/VMTranslator/docs/popSegment.md

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+`pop segment i`
+----
+
+where `segment in ["local", "argument", "this", "that"]`.
+
+We cannot actually directly store `RAM[SP]` in `RAM[D]`, since we have to store `RAM[SP]` in `D`. 
+So, intermediately, we store `RAM[D]` in `R13`, then retrieve `RAM[SP]` in `D` and finish.
+
+Output
+----
+
+```
+D <- segmentPointer + i  # D_eq_segmentPointer_p_i.asm
+SP--                     # SPmm.asm
+R13 <- D                 # R13_eq_D.asm
+RAM[R13] <- RAM[SP]      # RAM_R13_eq_RAM_SP.asm
+```