Hi Factor List,
I'm new to factor, and am in the 'kicking the tyres' stage.
Using a stack language is so different to anything else I'm used to
(scheme, python, C) that I've been struggling to grok the idiomatic ways
of doing things. I was hoping that somebody might be able to comment on
some code to point me in the right directions.
I'm writing a tool to index data. For this I need a mechanism to
generate sequential IDs for strings seen in the input data. It must
remember old strings and return their IDs, or generate a new ID if not
seen before.
After a few goes I came up with the code below, so I'm wondering:
- am I overusing variables to store state where I could be using the stack?
- are there any obvious features I'm missing that makes this easier?
(i.e. basically is there a cleaner way to solve the problem in factor?)
Any hints and pointers would be appreciated since I'm trying to work out
if factor may be a better general-purpose language than scheme for my needs.
Many thanks,
Phil
unittests
---------
(The public interface is with-idmap and str>id)
[ 0 ]
[ [ "hello" str>id ] with-idmap ] unit-test
[ 0 1 2 1 0 ]
[ [ { "s0" "s1" "s2" "s1" "s0" } [ str>id ] each ] with-idmap ] unit-test
implementation
--------------
<PRIVATE
SYMBOL: current-id
SYMBOL: ids-hash
: set-id ( id string -- )
ids-hash get set-at ;
: get-id ( string -- id/f )
ids-hash get at ;
: new-id ( -- id )
current-id dup inc get ;
: str>new-id ( string -- id )
new-id dup rot set-id ;
PRIVATE>
: with-idmap ( quotation -- )
[ H{ } clone ids-hash set
-1 current-id set
call ] with-scope ;
: str>id ( string -- id )
dup get-id [ swap drop ] [ str>new-id ] if* ;
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