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/04-indian-grouping.txt

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+== what the JDK gives for 123456789 ==
+String.format(en_IN, "%,d")      : 123,456,789
+String.format(hi_IN, "%,d")      : 123,456,789
+NumberFormat.getInstance(en_IN)   : 123,456,789
+NumberFormat currency (en_IN)     : ₹123,456,789.50
+CLDR pattern for en_IN            : #,##0.###
+
+== a DecimalFormat pattern that LOOKS like it should work ==
+pattern #,##,##0 -> grouping size : 3
+pattern #,##,##0 -> output        : 123,456,789
+
+== compact formatting knows crore but drops the digits ==
+compact (default rounding)        : 12Cr
+compact (2 fraction digits)       : 12.35Cr
+
+== IndianNumberFormat ==
+              0  ->  0
+            999  ->  999
+          1,000  ->  1,000
+         12,345  ->  12,345
+        123,456  ->  1,23,456
+      1,234,567  ->  12,34,567
+    123,456,789  ->  12,34,56,789
+   -123,456,789  ->  -12,34,56,789
+12,34,567.89
+-1,00,000.00
+Rs. 12,34,567.50
+
+== plugging it into a format string through %s ==
+Balance            9,87,65,432.10