Pop a snapshot from the Undo stack onto the current stack
The STKPOP command clears current stack and replaces it with a snapshot recalled from the top of the Undo stack. Subsequently the snapshot is removed from the Undo stack and all remaining snapshots drop one place.
The command has little utility in interactive mode, since each time a command is typed and XEQted a snapshot of the stack is already pushed on the Undo stack: the only effect of STKPOP would be to overwrite the current stack with a snapshot of itself.
This command is new in newRPL and does not exist in userRPL.
The following program
« 123 456 789 STKPUSH CLEAR 999 STKPOP »
creates the following stack (before STKPOP is executed):
1: 999 ……………………………………………………………………………………
The effect of STKPOP is to replace it with
3: 123 2: 456 1: 789 ……………………………………………………………………………………
| Command | Short Description | |
|---|---|---|
| CLEAR | Remove all objects from the stack | |
| DEPTH | Get the current stack depth | |
| DROP | Remove an object from the stack | |
| DROP2 | Remove two objects form the stack | |
| DROPN | Remove N objects from the stack | |
| DUP | Duplicate an object on the stack | |
| DUP2 | Duplicate two objects on the stack | |
| DUPDUP | Duplicate the same object twice on the stack | |
| DUPN | Duplicate a group of N objects | |
| NDUPN | Replicate one object N times and return N | |
| NIP | Remove object at level 2 on the stack | |
| OVER | Duplicate object at level 2 on the stack | |
| PICK | Duplicate object at position N on the stack | |
| PICK3 | Duplicate object at level 3 on the stack | |
| ROLL | Move object at level N to level 1 | |
| ROLLD | Move object from level 1 to level N | |
| ROT | Move object from level 3 to level 1 | |
| SWAP | Exchange objects in levels 1 and 2 | |
| UNPICK | Move object from level 1 to level N. | |
| UNROT | Move object from level 1 to level 3 | |
| IFT | Evaluate objects on the stack conditionally | |
| IFTE | Evaluate objects on the stack conditionally | |
| STKPUSH | Push a snapshot of the current stack on the undo stack | NEW |
| STKPOP | Pop a stack snapshot from the undo stack | NEW |
| STKDROP | Drop a snapshot from the undo stack | NEW |
| STKPICK | Copy snapshot in level N to the current stack | NEW |
| STKDEPTH | Get the depth of the undo stack | NEW |