add money library

extra/money/authors.txt

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+Doug Coleman
+Slava Pestov

extra/money/money-tests.factor

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+USING: money parser tools.test ;
+IN: temporary
+
+[ -1/10 ] [ DECIMAL: -.1 ] unit-test
+[ -1/10 ] [ DECIMAL: -0.1 ] unit-test
+[ -1/10 ] [ DECIMAL: -00.10 ] unit-test
+
+[ 0 ] [ DECIMAL: .0 ] unit-test
+[ 0 ] [ DECIMAL: 0.0 ] unit-test
+[ 0 ] [ DECIMAL: 0. ] unit-test
+[ 0 ] [ DECIMAL: 0 ] unit-test
+[ 1/10 ] [ DECIMAL: .1 ] unit-test
+[ 1/10 ] [ DECIMAL: 0.1 ] unit-test
+[ 1/10 ] [ DECIMAL: 00.10 ] unit-test
+
+
+
+[ "DECIMAL: ." eval ] must-fail
+[ "DECIMAL: f" eval ] must-fail
+[ "DECIMAL: 0.f" eval ] must-fail
+[ "DECIMAL: f.0" eval ] must-fail

extra/money/money.factor

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+USING: io kernel math math.functions math.parser parser
+namespaces sequences splitting combinators continuations
+sequences.lib ;
+IN: money
+
+: dollars/cents ( dollars -- dollars cents )
+    100 * 100 /mod round ;
+
+: money. ( object -- )
+    dollars/cents
+    [
+        "$" %
+        swap number>string
+        <reversed> 3 group "," join <reversed> %
+        "." % number>string 2 48 pad-left %
+    ] "" make print ;
+
+TUPLE: not-a-decimal ;
+: DECIMAL:
+    scan
+    "." split dup length 1 2 between? [
+        T{ not-a-decimal } throw
+    ] unless
+    ?first2
+    >r dup ?first CHAR: - = [ drop t "0" ] [ f swap ] if r>
+    [ dup empty? [ drop "0" ] when ] 2apply
+    dup length
+    >r [ string>number dup [ T{ not-a-decimal } throw ] unless ] 2apply r>
+    10 swap ^ / + swap [ neg ] when parsed ; parsing

extra/money/summary.txt

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+Utility for calculating money with rationals