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instance method

StringScanner#unscan

unscan

static VALUE
strscan_unscan(VALUE self)
{
    struct strscanner *p;

    GET_SCANNER(self, p);
    if (! MATCHED_P(p))
        rb_raise(ScanError, "unscan failed: previous match record not exist");
    p->curr = p->prev;
    CLEAR_MATCH_STATUS(p);
    return self;
}

Sets the scan pointer to the previous position. Only one previous position is remembered, and it changes with each scanning operation.

Example

s = StringScanner.new('test string')
s.scan(/\w+/)        # => "test"
s.unscan
s.scan(/../)         # => "te"
s.scan(/\d/)         # => nil
s.unscan             # ScanError: unscan failed: previous match record not exist

See also #terminate #values_at #string= also in 4.1 · 4.0 · 3.4 · 3.3 · 3.2 · 3.1

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