Template:Square root with defaults

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{{subst:subst}}square root with defaults|{{{1}}}|{{subst:#expr:{{subst:#ifeq:+|-|{{{2}}}|1}}/2+{{{1}}}/{{subst:#ifeq:+|-|{{{2}}}|1}}/2}}}}
{{subst:#ifeq:+|-|{{{2}}}|1}}

Substituting this template produces one or more new substitution template calls, allowing recursive change of a page, see Help:Recursive conversion of wikitext.