I didn't have time to get into this SRFI back when it was being discussed.

I happened to have an application that could benefit from it, so I dug myself in for the past few weeks.   Overall, I'm quite happy with the concept, the compose-ability, & the laziness.

I found & fixed lots of bugs to make it work better on my own Scheme as well as chibi.

I forked chibi and added my commits to https://github.com/jimrees/chibi-scheme .   I have made no other commits to that fork unrelated to (srfi 159) / (chibi show).

(srfi 130) dependency: the sample implementation relies on (chibi

string) which isn't quite (srfi 130):

The show sample implementation relies on:

(string-cursor-next str (string-cursor-end str)) ==> (string-cursor-end str)

...being able to call substring-cursor (substring/cursors) with only two arguments.

...being able to call substring (from (scheme base)) with only two arguments.

...being able to call string-cursor{<,<=,=,>=,>}? without the first string argument.

I was able to add a compatability layer to get around these dependencies for myself.   These have not been committed by my fork.

The documented test case for space-to shows an incorrect number of spaces.

Given the rule that columns are zero-based, the length of the following

string should be 6.

(show #f "a" (space-to 5) "b")

padded vs padded/left vs padded/right code vs. document

There is still confusion here.

Document says padded means padded/left.

Code & tests say padded means padded/right.

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forked vs. fn-forked

Documentation says forked.

Documentation discrepancies:

1) The third test case (numeric/si 608 " ") is missing a base,

sticking 1000 or 1024 both work.

2) The code rounds to one extra decimal place.  One test example

depends on rounding to 1 place, while the last two depend on rounding

to two places.

3) The "micro" character in the SRFI document for the last two test

cases are actually U+03BC, Greek Letter Mu.  The sample implementation

uses "micro" U+00B5.

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state variable WRITER, defaults to WRITTEN per the documentation.

But this implies WRITTEN serves as a default implementation for

writing, but the exact opposite is true.  WRITTEN applies the value

of WRITER, which defaults to #f, or WRITTEN-DEFAULT.

It would be safer to say that WRITTEN applies the WRITER variable, whose

default is implementation-specific.

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state variable DECIMAL-SEP, the doc says it defaults to "."

This is not quite accurate.  It defaults to #f.

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numeric default behavior with unusual radix'es:

(numeric foo 10 #f) invokes (number->string foo 10) which for an

inexact real is required by R7RS to print a minimal number of decimal

place to unabiguously represent the value.

So, then it follows that (numeric foo radix) (with precision == #f) should 

generate distinct strings for distinct inexact values of foo for every radix.

;; 1) number->string fails to do this in chibi for radix 10

(import (srfi 144))

(number->string (fladjacent 1.0 0.0)) ==> "1.0"

(number->string (fladjacent 1.0 2.0)) ==> "1.0"

;; 2) numeric fails to do this for all the other radixes

(show #f (numeric (fladjacent 1.0 0.0) 9)) ==> "1.0"

(show #f (numeric (fladjacent 1.0 2.0) 9)) ==> "1.0"