Hello,
I'm having a problem with understanding Parsing using recursion. The code
below consists of 4 tests.
Tests 1 and 4 produce the correct results, both in terms of the values in
the block and that they returns TRUE. The [none] in the rule makes this
happen.
Test 2 produces the correct values in the block but returns FALSE,
presumably because [none] is missing from the rule.
However why does Test 3 return TRUE but process the last input value
twice??
Mike.
REBOL []
check: func [
] [clear inps
probe parse "123+" col
print inps
clear inps
probe parse "123+456-" col
print inps
]
inps: []
digits: charset "0123456789"
num: [copy value [some digits] (value: to-decimal value)]
term: [num ["+" (insert tail inps value)|"-" (insert tail inps negate
value)]]
;Test 1
print "Test 1"
col: [term col | [none]]
check
;Test 2
print "Test 2"
col: [term col]
check
;Test 3
print "Test 3"
col: [term col | term]
check
;Test 4
print "Test 4"
col: [term col | term | [none]]
check
