string-format: String.format/formatted/printf cheat sheet module (specifier anatomy, rounding vs C printf, locales, Indian lakh/crore grouping Formatter cannot do, format exceptions, %t dates, concat cost), 11 contract tests

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ic4b7Sr2zcoRD2watXv1G

string-format/output/01-basics.txt

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+== conversions: what kind of value ==
+text | 42 | 3.141590 | ff | A | true
+== width: minimum characters ==
+[      ab] [ab      ] [      42] [42      ]
+== precision: digits after the point (f), or max chars (s) ==
+[3.14] [4] [   3.142] [abc]
+== flags ==
+[00042] [+42] [-42] [ 42] [(42)] [1,234,567]
+[0xff] [010] [FF] [-003.142]
+== argument index: reuse and reorder ==
+hello world
+echo, echo and again echo
+== %n and %% ==
+100% sure
+next line
+== %s accepts anything (calls String.valueOf / toString) ==
+[null] [7] [[1, 2]] [SHOUT]
+== %b is not 'is this the string true' ==
+true true false false
+== %c takes a char or a code point ==
+A A 😀