func()

in unicode/bidi/core.go [486:603]

• 80 lines of code
• 32 McCabe index (conditional complexity)

func (s *isolatingRunSequence) resolveWeakTypes() {

	// on entry, only these types remain
	s.assertOnly(L, R, AL, EN, ES, ET, AN, CS, B, S, WS, ON, NSM, LRI, RLI, FSI, PDI)

	// Rule W1.
	// Changes all NSMs.
	precedingCharacterType := s.sos
	for i, t := range s.types {
		if t == NSM {
			s.types[i] = precedingCharacterType
		} else {
			// if t.in(LRI, RLI, FSI, PDI) {
			// 	precedingCharacterType = ON
			// }
			precedingCharacterType = t
		}
	}

	// Rule W2.
	// EN does not change at the start of the run, because sos != AL.
	for i, t := range s.types {
		if t == EN {
			for j := i - 1; j >= 0; j-- {
				if t := s.types[j]; t.in(L, R, AL) {
					if t == AL {
						s.types[i] = AN
					}
					break
				}
			}
		}
	}

	// Rule W3.
	for i, t := range s.types {
		if t == AL {
			s.types[i] = R
		}
	}

	// Rule W4.
	// Since there must be values on both sides for this rule to have an
	// effect, the scan skips the first and last value.
	//
	// Although the scan proceeds left to right, and changes the type
	// values in a way that would appear to affect the computations
	// later in the scan, there is actually no problem. A change in the
	// current value can only affect the value to its immediate right,
	// and only affect it if it is ES or CS. But the current value can
	// only change if the value to its right is not ES or CS. Thus
	// either the current value will not change, or its change will have
	// no effect on the remainder of the analysis.

	for i := 1; i < s.Len()-1; i++ {
		t := s.types[i]
		if t == ES || t == CS {
			prevSepType := s.types[i-1]
			succSepType := s.types[i+1]
			if prevSepType == EN && succSepType == EN {
				s.types[i] = EN
			} else if s.types[i] == CS && prevSepType == AN && succSepType == AN {
				s.types[i] = AN
			}
		}
	}

	// Rule W5.
	for i, t := range s.types {
		if t == ET {
			// locate end of sequence
			runStart := i
			runEnd := s.findRunLimit(runStart, ET)

			// check values at ends of sequence
			t := s.sos
			if runStart > 0 {
				t = s.types[runStart-1]
			}
			if t != EN {
				t = s.eos
				if runEnd < len(s.types) {
					t = s.types[runEnd]
				}
			}
			if t == EN {
				setTypes(s.types[runStart:runEnd], EN)
			}
			// continue at end of sequence
			i = runEnd
		}
	}

	// Rule W6.
	for i, t := range s.types {
		if t.in(ES, ET, CS) {
			s.types[i] = ON
		}
	}

	// Rule W7.
	for i, t := range s.types {
		if t == EN {
			// set default if we reach start of run
			prevStrongType := s.sos
			for j := i - 1; j >= 0; j-- {
				t = s.types[j]
				if t == L || t == R { // AL's have been changed to R
					prevStrongType = t
					break
				}
			}
			if prevStrongType == L {
				s.types[i] = L
			}
		}
	}
}