/usr/share/hol88-2.02.19940316/Library/string/stringconv.ml is in hol88-library-source 2.02.19940316-31.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 | % ===================================================================== %
% FILE : stringconv.ml %
% DESCRIPTION : define the axiom scheme for character strings. %
% %
% %
% AUTHOR : T. Melham %
% DATE : 87.08.23 %
% REVISED : 90.10.27 %
% ===================================================================== %
% --------------------------------------------------------------------- %
% string_CONV "defines" the infinite family of constants: %
% %
% 'a' = STRING(ASCII F T T F F F F T)`` %
% 'ab' = STRING(ASCII F T T F F F F T)`b` %
% %
% ... etc %
% %
% The auxiliary function bits n m computes the representation in n %
% bits of m (MOD 2**n) %
% --------------------------------------------------------------------- %
let string_CONV =
let T = "T" and F = "F" and A = "ASCII" in
let STR = curry mk_comb "STRING" in
let chkty = assert (\t.fst(dest_type t) = `string`) in
letrec bits n m =
if (n=0) then [] else
let hm = m/2 in (hm*2 = m => F | T) . bits (n-1) hm in
\tm. (let str,ty = (I # chkty) (dest_const tm) in
if (str = `\`\``) then fail else
let q.h.t = explode str in
let code = rev (bits 8 (ascii_code h)) in
let tm1 = STR (list_mk_comb(A,code)) in
let def = mk_comb(tm1,mk_const(implode (q.t),ty)) in
mk_thm([], mk_eq(tm,def))) ?
failwith `string_CONV`;;
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