Erlang (programming language)/Tutorials/Command Line: Difference between revisions
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imported>Eric Evers (New page: Getting to know the erlang command line. Erlang has a command line like lisp, python and prolog. In the erlang command line you may not reuse a variable, unless you force it to forget wi...) |
imported>Eric Evers No edit summary |
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Questions: | Questions: | ||
1) | 1) Assume Q=[[a,b],[a,b]]. Is the head of Q equal to the tail of Q? | ||
Why? | |||
2) Is the length of A++B always longer the either A or B? | 2) Is the length of A++B always longer the either A or B? | ||
Can you give a counter example? | |||
3) Is the lenght of A--B always shorter than A? | 3) Is the lenght of A--B always shorter than A? | ||
Can you give a counter example? | |||
Revision as of 13:34, 27 August 2008
Getting to know the erlang command line.
Erlang has a command line like lisp, python and prolog. In the erlang command line you may not reuse a variable, unless you force it to forget with f(). f() makes it forget all variables. Let us do some simple list manipulations at the command line with head, hd(), and tail, tl().
[reason7@localhost ~]$ erl Eshell V5.5 (abort with ^G)
1> L = [b,c,d,5]. [b,c,d,5]
2> hd(L) = b
3> H = [f,t]. [f,t]
4> H++L. [f,t,b,c,d,5]
5> Q = [[a,b],[a,b]]. [[a,b],[a,b]]
6> hd(Q). [a,b]
7> tl(Q). [ [a,b ] ]
Questions:
1) Assume Q=[[a,b],[a,b]]. Is the head of Q equal to the tail of Q? Why?
2) Is the length of A++B always longer the either A or B? Can you give a counter example?
3) Is the lenght of A--B always shorter than A? Can you give a counter example?