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|
#! /usr/bin/env gforth
\ Challenge 095
\
\ TASK #2 › Demo Stack
\ Submitted by: Mohammad S Anwar
\ Write a script to demonstrate Stack operations like below:
\
\ push($n) - add $n to the stack
\ pop() - remove the top element
\ top() - get the top element
\ min() - return the minimum element
\
\ Example:
\ my $stack = Stack->new;
\ $stack->push(2);
\ $stack->push(-1);
\ $stack->push(0);
\ $stack->pop; # removes 0
\ print $stack->top; # prints -1
\ $stack->push(0);
\ print $stack->min; # prints -1
100 CONSTANT stack_size
CREATE stack stack_size CELLS ALLOT \ create stack
VARIABLE stack_ptr
-1 stack_ptr ! \ init empty stack
: stack.top-addr ( -- addr )
stack stack_ptr @ CELLS +
;
: stack.push ( n -- )
1 stack_ptr +! \ increment stack pointer
stack.top-addr !
;
: stack.pop ( -- )
-1 stack_ptr +! \ decrement stack pointer
;
: stack.top ( -- n )
stack.top-addr @ \ return data at top of stack
;
: stack.min ( -- n )
stack @ \ init minimum
stack_ptr @ 1+ 0 ?DO
stack I CELLS + @
MIN
LOOP
;
\ example
\ my $stack = Stack->new;
2 stack.push \ $stack->push(2);
-1 stack.push \ $stack->push(-1);
0 stack.push \ $stack->push(0);
stack.pop \ $stack->pop; # removes 0
stack.top . CR \ print $stack->top; # prints -1
0 stack.push \ $stack->push(0);
stack.min . CR \ print $stack->top; # prints -1
BYE
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