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If a pop operation on the stack causes the stack pointer to move past the origin of the stack, a stack underflow occurs. If a push operation causes the stack pointer to increment or decrement beyond the maximum extent of the stack, a stack overflow occurs. Some environments that rely heavily on stacks may provide additional operations, for example:
This type of stack is also known as an execution stack, program stack, control stack, run-time stack, or machine stack, and is often shortened to simply the "stack". Although maintenance of the call stack is important for the proper functioning of most software , the details are normally hidden and automatic in high-level programming languages .
Commonly provided are dup, to duplicate the element atop the stack, exch (or swap), to exchange elements atop the stack (the first becomes second and the second becomes first), roll, to cyclically permute elements in the stack or on part of the stack, pop (or drop), to discard the element atop the stack (push is implicit), and others. These ...
A push operation decrements the pointer and copies the data to the stack; a pop operation copies data from the stack and then increments the pointer. Each procedure called in the program stores procedure return information (in yellow) and local data (in other colors) by pushing them onto the stack.
With a stack stored completely in RAM, this does implicit writes and reads of the in-memory stack: Load X, push to memory; Load 1, push to memory; Pop 2 values from memory, add, and push result to memory; for a total of 5 data cache references. The next step up from this is a stack machine or interpreter with a single top-of-stack register.
In the operational definition of an abstract stack, push(S, x) returns nothing and pop(S) yields the value as the result but not the new state of the stack. There is then the constraint that, for any value x and any abstract variable V, the sequence of operations { push(S, x); V ← pop(S) } is equivalent to V ← x.
Don’t skip the parsley and tarragon as both add a nice pop of color, and their flavors play so well with the mushrooms. View Recipe. 3-Ingredient Roasted Red Pepper Soup with Chickpeas.
Input: 3 + 4 Push 3 to the output queue (whenever a number is read it is pushed to the output); Push + (or its ID) onto the operator stack; Push 4 to the output queue; After reading the expression, pop the operators off the stack and add them to the output.