Stacks

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Chapter 7 Stacks
Stacks Further Stack Examples Pushing/Popping
a Stack Class Stack (3 slides) Using a Stack to
Create a Hex Uncoupling Stack Elts (6
slides) Activation Records RPN
Infix Notation Summary Slides (4 slides)
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Stacks

• A stack is a sequence of items that are
  accessible at only one end of the sequence.

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Further Stack Examples
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Pushing/Popping a Stack

• Because a pop removes the item last added to the
  stack, we say that a stack has LIFO
  (last-in/first-out) ordering.

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Using a Stack to Create a Hex Number
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Uncoupling Stack Elements
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Uncoupling Stack Elements
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Uncoupling Stack Elements
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Uncoupling Stack Elements
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Uncoupling Stack Elements
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Uncoupling Stack Elements
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Infix Expression Rules   The figure below gives
input precedence, stack precedence, and rank used
for the operators , -, , /, , and , along
with the parentheses. Except for the exponential
operator , the other binary operators are
left-associative and have equal input and stack
precedence.
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Summary Slide 1
- Stack - Storage Structure with insert (push)
and erase (pop) operations occur at one end,
called the top of the stack. - The last
element in is the first element out of the
stack, so a stack is a LIFO structure.
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Summary Slide 2
- Recursion - The system maintains a stack of
activation records that specify 1) the
function arguments 2) the local
variables/objects 3) the return
address - The system pushes an activation record
when calling a function and pops it when
returning.
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Summary Slide 3
- Postfix/RPN Expression Notation - places the
operator after its operands - easy to evaluate
using a single stack to hold operands.
- The rules 1) Immediately push an operand
onto the stack. 2) For a binary operator, pop
the stack twice, perform the operation, and
push the result onto the stack. 3) At the end
a single value remains on the stack. This is
the value of the expression.
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Summary Slide 4
- Infix notation - A binary operator appears
between its operands. - More complex than
postfix, because it requires the use of
operator precedence and parentheses. - In
addition, some operators are left-associative,
and a few are right-associative.